Introduction

The escalating cost of textbooks and instructional materials is a global concern for higher education. In the USA, for example, during 2018–2019, students in 4-year public institutions paid on average $1272 USD in books and supplies per year in addition to $9126 paid in tuition and fees (National Center for Education Statistics, 2019). Similar textbook and instructional costs are found in Canada where students pay between $800 and $1000 CAD per year for these materials (Government of Canada, 2022). Increasing textbook and material costs are also seen in the UK where book and equipment costs increased approximately £115 between 2011–2012 and 2014–2015 (Pitt et al., 2019). Textbook costs in the Global South are even higher due in part to the costs associated with importing them from the Global North (Arinto et al., 2017). These costs impact students both academically and financially.

Students suffer academically because high price contributes to not purchasing required materials and books. In one survey, nearly 54% did not purchase required materials, while 32% of those same students reported that lack of required materials resulted in earning a poorer grade (Florida Virtual Campus, 2022). Book and material requirements also impact the number of courses students take and course enrollment. Students take fewer courses, opt out from specific courses, or drop courses because of the cost of textbooks and instructional materials (Florida Virtual Campus, 2022).

Cost is a primary factor influencing students’ higher education enrollment decisions (Rowan-Kenyon, 2007) and has a stronger influence on low-income students than their more affluent peers (Declercq & Verboven, 2015). For example, only 47% of students in the 38 Organisation for Economic Cooperation and Development (OECD) member countries come from a lower socioeconomic status (OECD, 2019b). Examining participation rates based on income quartile reveals wide disparities between the highest and lowest quartiles globally. In the USA, for example, 48% of students in the lowest quartile compared to 78% of those in the highest attend college (Pell Institute, 2021). The impact of income on higher education is even more pronounced in many countries of the Global South (Arinto et al., 2017). For example, in Vietnam, just over 4% of individuals from the poorest quartile attend a higher education institute compared to over 64% of those from the richest quartile (UNESCO, 2023). As a result, there is a disproportional impact on the enrollment probability of disadvantaged groups in higher education compared to their more affluent peers (Pell Institute, 2021).

Socioeconomic status has a further impact on completion rates and time to degree attainment (OECD, 2019a). Students from higher socioeconomic statuses complete their educational programs within 3 years over the expected duration at higher rates than those from lower socioeconomic statuses (OECD, 2019a). This difference in completion rate varies from as low as 5% in countries such as Estonia and Portugal to as high as 20% in countries like the USA (OECD, 2019a). Without question, limited higher education inhibits earning power and restricts social mobility (Murphy, 2020; OECD, 2019a; U.S. Bureau of Labor, 2020). Mediating disparities is one reason that educational policies worldwide have sought to address cost and increase educational access.

One cost mitigation strategy is the use of open educational resources (OER), defined as “learning, teaching and research materials in any format and medium that reside in the public domain or are under copyright that have been released under an open license, that permit no-cost access, re-use, re-purpose, adaptation and redistribution by others” (UNESCO, 2019, p. 5). These materials were initially advocated during 2002 by the United Nations Educational, Scientific, and Cultural Organization (UNESCO) and are an extension of the Universal Declaration of Human Rights which promotes the right to education (UNESCO, 2019). OER were designed to increase educational access and to help eliminate financial barriers related to cost, while supporting “quality education that is equitable, inclusive, open and participatory” (UNESCO, 2019, p. 4). As a result, OER provide an opportunity for promoting educational transformation through increased access and cost reduction (Butcher, 2015).

Key to this transformative power is the adaptability of these resources. OER are flexible materials that can be customized to specific courses to better meet their objectives (DeRosa & Robison, 2017). In addition, OER can be modified to be more locally relevant, directly tied to the cultures in which courses are taught and translated into local languages (Biswas-Diener & Jhangiani, 2017; UNESCO, 2019). These materials can be interactive and promote engagement (Biswas-Diener & Jhangiani, 2017). OER also provide opportunities for collaboration between faculty and staff that empowers individuals to work together (DeRosa & Robison, 2017). Because these materials are more easily shared, they provide opportunities for instructors to build on each other’s innovations (Biswas-Diener & Jhangiani, 2017). As a result of this collaborative process, OER reframe the relationship between students and instructors, reconceptualizing students’ role as learners from merely receiving knowledge to actively engaging with and creating knowledge (Butcher, 2015; DeRosa & Robison, 2017). These educational benefits are further supported by the cost savings afforded by OER.

OER provide a free alternative to commercial textbooks and instructional materials that enable more students to obtain their required materials and gain access on the first day of class. Grimaldi et al. (2019) argued that easy access improves academic outcomes by increasing the number of students who have required materials. As a result, OER should have a greater proportional impact on students who may not otherwise be able to obtain course materials (Grimaldi et al., 2019). OER allow faculty to begin their courses with the knowledge that all students, regardless of their financial resources, have the required materials needed for academic success.

Globally, educational policies have provided support for initiatives seeking to reduce educational costs and increase access. In the USA, nineteen states have enacted OER statutes or state-funded initiatives supporting these materials (SPARC, 2018). For example, Florida and California passed legislation to establish organizations responsible for hosting, promoting, and providing recommendations on the use of open-access textbooks and educational resources to reduce educational costs (Academic Materials, 2020; Florida Postsecondary Academic Library Network, 2021). In addition to establishing organizations that promote the use of OER, states such as Florida have enacted legislation that requires cost to be a consideration when seeking course materials. Florida statute 1004.085 (2022) requires state universities and colleges to publicly post for five years lists of all required and recommended instructional materials at least 45 days prior to the start of an academic semester. In addition, the statute requires instructors or academic departments to determine if OER are a viable option for their courses based in part on the financial impact to students. Similar policies exist in the European Union where 20 member states have policies with open education components ranging from those that directly promote OER to those that include open education with other educational strategies and initiatives (dos Santos et al., 2017).

Gaps in Existing Reviews

Existing reviews of OER research focus on the impacts that adoption has on outcomes as well as faculty and student perceptions of their quality. Clinton (2019), Clinton and Khan (2019), and Hilton (2016, 2019) synthesized the literature on student outcomes and faculty and student perceptions of OER. They found that students generally perform as well as or better when using OER as they do when using commercial materials. In addition, students and faculty generally had positive views of the quality of these materials. However, existing reviews are limited by their timeframes and their focus on cost and general perceptions. Except for Clinton and Khan (2019), none of the reviews included articles that were published after 2018. OER research is on the rise and 37 studies on perceptions and efficacy of these materials were published in peer-reviewed journals since these reviews. Clinton (2019), Clinton and Khan (2019), and Hilton (2016, 2019) examined student outcomes across all measures of success, combining analysis of final course grades with withdrawal rates, exam grades, and non-course specific outcomes. Conflation could result in an over- or under-estimation of the impact of OER on student outcomes. Additionally, discussions of faculty and student perceptions are limited to perceptions of quality and helpfulness but do not include discussions of barriers or incentives to adopt or challenges and benefits of using these materials.

Existing reviews are further limited by their methodological design. Except for Clinton and Khan (2019), current reviews of OER research are non-systematic as defined by Page et al. (2021), providing only a descriptive synthesis of findings, and have narrow inclusion criteria. Non-systematic reviews such as narrative and descriptive reviews differ methodologically and in purpose to systematic reviews. Narrative and descriptive reviews provide an overview of existing research by summarizing and synthesizing results to find trends and patterns (Paré et al., 2015). Non-systematic reviews provide scant details on how included studies were identified, selected, and evaluated, limiting their replicability (Paré et al., 2015). Systematic reviews, on the other hand, aggregate and integrate empirical results quantitatively or qualitatively to answer research questions and identify methodological and quality issues of existing research studies (Page et al., 2021; Paré et al., 2015). Systematic reviews follow established research protocols and provide details on the methods used to identify, select, and evaluate research studies to increase research transparency and promote replicability (Page et al., 2021).

Clinton (2019), for example, conducted a narrative review of student outcomes and perceptions of OER in postsecondary psychology courses. Hilton’s (2016, 2019) reviews synthesized findings on OER in postsecondary education but excluded all studies with fewer than 50 participants. This limits the number of perception studies analyzed and potentially excluded qualitative research with more in-depth information on how faculty view these materials. Clinton and Khan (2019) performed a meta-analysis of findings on the impact of using open access textbooks on student outcomes. In addition to limiting their definition of OER to open access textbooks, Clinton and Khan (2019) only included studies that provided adequate statistics for conducting a meta-analysis. Focusing on textbooks excludes many types of OER that are implemented in courses and potentially under- or over-estimates the impact that OER has on student outcomes. This literature review supplements these studies by conducting a systematic review (Page et al., 2021) and seeks to fill existing gaps in the literature.

Existing reviews lack a theoretical framework for analyzing OER research. Clinton (2018) used the COUP framework to organize the results of her review. The COUP framework is an approach to studying OER impact and stands for cost, outcomes, usage, and perceptions (Open Education Group, n.d.). While this framework provides a useful strategy for organizing results, it does not rely on theory. Instead, it provides a list of questions in these four areas that researchers can use when analyzing OER impact. This review addresses this gap by using self-determination theory (SDT). SDT, a broad motivational framework, explains the importance of meeting basic psychological needs for promoting motivation and focuses on the needs for autonomy, competency, and relatedness (Ryan & Deci, 2020). Autonomy describes the feeling of control or ownership that an individual feels over their behavior, competency is the degree to which an individual feels they have expertise or the ability to succeed, and relatedness is how connected a person feels to their culture and peers (Ryan & Deci, 2020). SDT has been applied to a variety of higher education practices, including syllabi language (Tamayo et al., 2022) and faculty motivation (Yasué et al., 2019). In addition, Ford and Alemneh (2021) and Herbert et al. (2023) proposed SDT as a framework for analyzing OER.

SDT is an appropriate lens to examine OER because it provides an explanatory framework for how these materials can help meet faculty and students’ basic psychological needs. OER can promote autonomy by providing faculty with more course material choices that enable them to enact their course visions (Ford & Alemneh, 2021). Adaptation of commercial materials is limited by copyright laws. OER, on the other hand, are adaptable materials that faculty can adjust to meet their course goals and course structure. In addition, OER promote inclusivity by removing financial barriers to inclusion. Financial barriers to inclusion reduce students’ belongingness, especially for low-income students who feel excluded due to being unable to afford required course materials (Nguyen & Herron, 2021). As a result, OER can promote relatedness, or students’ sense of belonging on campus, by eliminating this financial barrier.

The purpose of this systematic review is to synthesize disparate findings and provide an analysis of barriers and incentives to adoption and use. This review expands on previous reviews by systematizing a disparate field and analyzing previously excluded topics. We addressed three research questions:

  1. 1.

    What are student perceptions and faculty perceptions of OER?

  2. 2.

    What incentives and barriers impact OER adoption and use?

  3. 3.

    What is the impact of OER on student achievement?

Methods

This review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) 2020 guidelines (Page et al., 2021). Page et al. (2021) stated that for a review to be considered systematic it must include a discussion of eligibility criteria, the search and selection process, and details on how data was collected and analyzed.

Eligibility Criteria

Five inclusion criteria were used. First, studies had to be published in a peer-reviewed journal between 2002 and 2023 and examine open educational resources in a postsecondary setting. Inclusion required a focus on faculty perceptions, faculty motives and barriers to adopt OER, student perceptions, or student outcomes. Studies had to be published in English. This review expanded the inclusion criteria of Clinton (2019), Clinton and Khan (2019), and Hilton (2016, 2019) by including studies of all sample sizes, sampling methods, analysis types, academic fields, and OER formats. All included studies employed a quantitative or qualitative research design such as experimental, quasi-experimental, survey, or case study.

Sources, Search Strategy, and Selection Processes

Studies were identified through a search of Academic Search Premier and Google Scholar conducted through April 2023 using combinations of the terms open educational resources, OER, faculty perceptions, faculty beliefs, faculty motivations, student perceptions, student success, student outcomes, and student achievement. Initial search parameters were limited by language and publication year. The initial search produced 1276 records. Two hundred and three duplicates and 585 non-journal entries were removed from the initial search results. Both authors screened journal titles to verify inclusion. Authors discussed disagreements until a consensus was reached. One author then reviewed the abstracts of the remaining articles to determine if they met inclusion criteria. Three hundred and twenty-nine articles were removed after reviews of title (n = 195) and abstract (n = 184). Articles meeting inclusion based on a screening of title and abstract were read in full. An additional 19 articles were removed after this review. Seven additional articles were identified using forward and backward searches of selected articles, resulting in a final sample of 97 reports. The search and selection process is further detailed in Fig. 1.

Fig. 1
figure 1

Search and screening process

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Data Collection and Synthesis Methods

Details from reviewed articles were analyzed and synthesized based on the type of research question. First, one author examined studies to determine their method of data analysis and categorized them as either inferential or descriptive and qualitative. This same author recorded bibliographical information, research design, participant type, number of participants, operational definition of academic outcome, differences in performance between students using OER and commercial materials, and effect sizes in Tables 1 and 2. Participant type was further categorized as student or faculty. Operational definitions of academic outcome were listed based on how the study measured this term and include course grade, exam grade, course throughput rate, drop, fail, and withdrawal (DFW) and completion rates, and non-course specific measures.

Table 1 Description of studies: inferential analyses
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Table 2 Description of studies: descriptive and qualitative analyses
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Studies were then categorized based on their research questions as student perceptions, faculty perceptions, barriers and incentives, and academic outcomes and were included in all categories they addressed. These categories were analyzed thematically. Thematic analysis, a qualitative method that is used to identify recurrent themes across studies (Popay et al., 2006), was deemed appropriate because quantitative and qualitative analyses were reviewed.

Results

Perceptions

Of the 97 studies reviewed, 67 discussed student or faculty perceptions of OER. As indicated in Tables 1 and 2, most of these studies used surveys and descriptive results narrative. These studies focused on student and faculty views of the quality of OER.

Forty-eight studies examined student perceptions of OER. Across studies, students believed that OER are as good as or better in quality than materials they used in other courses. These studies do not define quality and leave interpretation to respondents. Quality is measured using Likert-scale responses and participants are asked to report their perceptions of OER. These decisions are made as a comparison to other materials and follow-up questions are not asked. As such, these subjective findings should be viewed cautiously because it is unclear how students are defining the term “quality.” In an experimental study comparing student perceptions of passages from OER and commercial textbooks, students reported that their ratings of de-identified passages changed when bibliographical data such as material cost and publication date was revealed (Sheu & Grissett, 2020). This study took place in a laboratory with randomly selected passages that were not directly connected to students’ courses. Survey results on views of OER used within a class asked students to compare OER materials to their other course materials. For example, Kersey (2019b) surveyed students in a calculus course about their views of OER compared to commercial materials by asking to what degree students believed that free materials are as good as paid materials. As a result, what is measured through these questions might not be views of quality so much as how much a student liked the material. Factors such as frequency of use, cost, and interest in the subject may impact answer choices. In addition, students may be comparing OER in one subject to commercial materials in a different subject and their personal interest in these topics may impact their responses. Despite these concerns, this subjective view of OER quality is also held by faculty.

Thirty-five studies, including 16 that discussed student perceptions, evaluated faculty perceptions of OER. The findings of these studies varied more widely than student perceptions with faculty beliefs about OER quality tied to their familiarity and adoption of these resources. In four studies, faculty who had not adopted OER expressed negative views of these resources including concerns about quality or beliefs that OER are inferior to commercial materials (Anderson et al., 2017; Belikov & Bodily, 2016; Magro & Tabaei, 2020; Martin & Kimmons, 2020). In other studies, faculty who adopted OER tended to view these materials as being similar in quality or higher quality compared to commercial textbooks (Abramovich & McBride, 2018; Bliss et al., 2013a; Bliss et al., 2013b; Bond et al., 2021; Coleman-Prisco, 2017; Hilton et al., 2013; Jaggars et al., 2018; Jung et al., 2017; Lantrip & Ray, 2020; Ozdemir & Hendricks, 2017; Pounds & Bostock, 2019; Vander Waal Mills et al., 2019; Watson et al., 2017). Baas et al. (2022) directly analyzed the impact that familiarity with OER had on beliefs about their quality and concluded that as faculty gained familiarity with these materials, they grew less skeptical about their quality. Like examinations of student perceptions, these studies did not define quality and what makes a quality educational resource is left to faculty respondents to determine.

Faculty beliefs about what constitutes quality educational resources, the usefulness and relevance of materials to their teaching, the benefits of materials to students, and the compatibility of materials with pedagogical beliefs impact assessment of OER quality. These contributing characteristics to assessing quality are identified by faculty in Likert-scale responses, self-reports, and interview questions on important characteristics of OER and strategies for finding these materials. Faculty reported that they trusted materials produced by prestigious authors and institutions more than other materials (Baas et al., 2019; Pitt, 2015; Pounds & Bostock, 2019). Survey responses indicated faculty were more likely to adopt OER that were produced by a reputable author or organization (Pitt, 2015). Other studies found usefulness and relevancy (Harold & Rolfe, 2019; Jaggars et al., 2018), helpfulness for students (Abramovich & McBride, 2018; Coleman-Prisco, 2017), and compatibility with teaching and learning beliefs (Coleman-Prisco, 2017; Delimont et al., 2016) influenced quality considerations.

Barriers and Incentives

Fifty-nine studies discussed barriers and incentives to OER adoption and use. As indicated in Tables 1 and 2, these studies used a combination of focus groups and surveys. Several trends emerged across studies and faculty and students identified common barriers and incentives to using OER. While there are some similarities in responses, faculty and students also reported incentives and barriers that were unique to their experiences.

Barriers

Students identified a variety of barriers to using OER. Students cited a preference for printed materials as the most common challenge (Anderson & Cuttler, 2020; Jhangiani & Jhangiani, 2017; Jhangiani et al., 2018; Lin, 2019). Students disliked the lack of tactility associated with digital materials and believed print materials were more convenient to read and highlight (Anderson & Cuttler, 2020; Jhangiani & Jhangiani, 2017; Jhangiani et al., 2018; Lin, 2019). In one study, students reported self-regulation issues when using OER because of their interactive designs and the ability to explore additional information at their own pace (Lin, 2019). The design of OER may place additional strain on students’ cognitive load by providing ample distractions under the guise of additional resources. Adding to this additional load on cognitive functioning is the frustration some students encounter with technological issues when using OER.

Technological barriers center on access, categorization, and difficulty adapting course materials. In three studies, students reported difficulties accessing OER due to challenges locating them or not having consistent internet access (Lawrence & Lester, 2018; Lin, 2019; Vollman, 2021). Inconsistent internet access is an issue that directly impacts the students who may benefit the most from OER. A 2020 study revealed that 59% of school-aged children who were lower-income faced digital obstacles in conducting remote schooling such as a lack of reliable home internet, no home computer, or having to use a smart phone to complete schoolwork (Vogels, 2021). Faculty reported similar issues with locating OER to adopt for their courses. Lack of effective search capabilities, including repositories for materials, was a primary issue that faculty faced in locating OER (Belikov & Bodily, 2016; Martin & Kimmons, 2020; Martin et al., 2017; Nagashima & Hrach, 2021; Pitt, 2015; Pitt et al., 2020). Existing OER repositories can be cumbersome and difficult to navigate. The MERLOT repository, for example, provides a list of OER that can be searched using keywords and material type, but contains everything from free Kindle books to open website textbooks of unknown quality. This lack of technological solutions to OER cataloging and the ensuing requirement to search through lengthy lists of materials of varying quality to find appropriate resources can lead to frustration and discouragement. When materials are found they often need to be modified or adapted to fit the needs of the course requiring additional technical knowledge to effectively adapt and edit existing materials. Faculty described challenges with modifying downloaded OER due to unclear instructions, lack of appropriate software, or cumbersome processes requiring multiple steps and multiple software programs (Martin & Kimmons, 2020). The adaptation process involves a substantial time commitment.

Faculty reported the time-consuming process of finding, adopting, and adapting OER as a major barrier to adoption. In thirteen studies, faculty perceived the time it takes to find OER and adapt them as prohibitive and a primary barrier to their adoption (Baas et al., 2022; Belikov & Bodily, 2016; Cardoso et al., 2019; Delimont et al., 2016; Hassall & Lewis, 2017; Lantrip & Ray, 2020; Martin & Kimmons, 2020; Martin et al., 2017; Nagashima & Hrach, 2021; Oelfke et al., 2021; Petrides et al., 2011; Tillinghast, 2021; Watson et al., 2017). In addition to the time required to locate materials, OER present an additional time-constraint in preparing for class due to the time needed to adapt these resources and the lack of ancillary materials such as test banks and sample questions. Faculty spend more time preparing for class when using OER as compared to commercial textbooks (Bliss et al., 2013a, 2013b; Chetna, 2021; Magro & Tabaei, 2020). Faculty who use OER must devote more time to finding appropriate materials, which often involves evaluating unorganized lists of materials for relevance and quality. Once appropriate materials are found they must be adapted to fit instructional needs. Even when native materials can be used the process of incorporating resources into a course involves making changes, especially in classes that rely on sample problems and online homework platforms. The amount of time required to find, adapt, and incorporate OER into courses is often substantially more than using commercial materials that are frequently advertised by publishers and contain supplementary materials. This additional time can lead to the belief that using these materials are not worthwhile as faculty have other obligations that require their time and expertise.

Faculty reported inadequate institutional support as a barrier affecting their decision to adopt OER. Institutional support can include providing resources such as experts in OER as well as providing recognition for adopting, adapting, and creating these materials. Faculty believed institutions need to provide technical and copyright support to better facilitate OER adoption (Baas et al., 2019; Bliss et al., 2013b; Delimont et al., 2016; Hassall & Lewis, 2017; Lantrip & Ray, 2020; Martin et al., 2017; Petrides et al., 2011). Faculty reluctance to adopt and create OER was tied to their perceptions of the value their institutions placed on these resources (Cardoso et al., 2019; Martin & Kimmons, 2020; Pitt et al., 2020). Martin & Kimmons (2020), for example, concluded that faculty did not allocate their time to finding OER because of competing professional obligations such as research that were more valued by their institutions. This lack of support is echoed in findings from five studies which indicated lack of recognition of OER authorship by departments and colleagues hindered adoption (Bond et al., 2021; Cardoso et al., 2019; Hassall & Lewis, 2017; Lantrip & Ray, 2020; Watson et al., 2017). Institutional pressures on faculty for research, teaching, and service make the time-consuming process of adoption and adaptation of OER nearly prohibitive, especially in institutions that do not recognize this development as part of the promotion and tenure process. Institutions not valuing OER as part of scholarship or research combined with existing job-related pressures force faculty to make judgements about the best use of their time. One of the factors that faculty take into consideration in making these decisions is the benefits afforded by using OER.

Incentives

Our review of studies verified that students and faculty identified cost savings as the primary incentive to using OER. This is unsurprising given student reports on the negative impact of cost on their education (Fischer et al., 2020; Jhangiani & Jhangiani, 2017; Martin et al., 2017). The results of nine studies indicated faculty are aware of the burden that textbook costs place on students and are motivated to adopt these materials to help offset student costs (Bliss et al., 2013b; Bond et al., 2021; Coleman-Prisco, 2017; Jung et al., 2017; Lantrip & Ray, 2020; Ozdemir & Hendricks, 2017; Petrides et al., 2011; Pitt, 2015; Tillinghast, 2021). This awareness has led to programs like Florida’s Affordability Counts program. Affordability Counts provides both a list of courses across the Florida state system that use low-cost materials as well as a badge that faculty can imbed into their course syllabi and online courses to inform students of the use of these affordable materials (Affordability Counts, 2022). Students appreciated the cost savings associated with OER and valued instructors’ efforts to reduce costs (Choi & Carpenter, 2017; Farrow et al., 2015; Fine & Read, 2020; Ikahihifo et al., 2017; Jhangiani & Jhangiani, 2017; Kinskey et al., 2018; Lin, 2019; Magro & Tabaei, 2020; Ozdemir & Hendricks, 2017; Petrides et al., 2011; Ross et al., 2018; Sheu & Grissett, 2020; Vojtech & Grissett, 2017; Vollman, 2021; Watson et al., 2017). Students rated instructors using OER as kinder, more encouraging, and more creative than those using commercial textbooks (Vojtech & Grissett, 2017). As freely available resources, OER have the potential to save students hundreds of dollars. These cost savings are used by students to reinvest in their education or to defray their daily living expenses leading to lowered stress and improved mental health (Collins et al., 2020; Ikahihifo et al., 2017; Jhangiani & Jhangiani, 2017; Martin et al., 2017; Sanchez et al., 2021; Vollman, 2021). Students associated OER with reduced stress due to having access to the materials from the start of class (Vollman, 2021). By reducing anxiety and stress, OER can have a further positive impact on academic outcomes by reducing extraneous cognitive load caused by negative emotions (Plass & Kalyuga, 2019). When students worry less, they can focus more on their academics and less on their financial burdens. As free materials, students do not have to wait to have the funds to purchase materials and can access them on the first day of courses.

Increased access was reported by students and faculty as an incentive to using OER. Students and faculty appreciated the ability to access materials on the first day of classes (Ikahihifo et al., 2017; Lantrip & Ray, 2020; Magro & Tabaei, 2020; Martin et al., 2017; Ozdemir & Hendricks, 2017; Pitt, 2015; Ross et al., 2018; Ryan & Nawalaniec, 2021; Sanchez et al., 2021; Sheu & Grissett, 2020; Tillinghast, 2021; Young, 2016). Because students have access to their materials on the first day of class faculty can begin their instruction with the knowledge that all students have the materials needed to be successful in the course. In addition, students identified portability as a benefit to using OER (Feldstein et al., 2012; Jhangiani & Jhangiani, 2017; Lin, 2019; Petrides et al., 2011; Ross et al., 2018; Verkuyl et al., 2023). In a survey of students, Jhangiani & Jhangiani (2017) determined that just over half of students believed OER’s convenience and portability was a very important or essential characteristic of these materials. This access to resources may be especially important for students who have historically been excluded from higher education such as low-income students and non-traditional students who may have to work to pay for their educational expenses. Increased access and flexibility in use allow students to be better prepared for class from the start and provide students with opportunities to further their educational aims.

OER are beneficial for meeting students’ academic goals. Students believed these materials helped them in meeting their instructors’ stated course objectives (Abramovich & McBride, 2018; Cooney, 2017; Feldstein et al., 2012; Finlayson, 2020; Gil et al., 2013; Lin, 2019; Oelfke et al., 2021; Ryan & Nawalaniec, 2021). For example, Cooney (2017) surveyed students on the use of OER and concluded most believed that their course materials supported their learning. In addition, students believed OER were as helpful as other materials in meeting academic goals (Abramovich & McBride, 2018; Bliss et al., 2013b; Collins et al., 2020; Kersey, 2019b; Kinskey et al., 2018) with results from one survey indicating that 86% of students believed that OER were as useful or more useful than other materials in meeting course objectives (Abramovich & McBride, 2018). These materials can be customized by instructors to reach desired learning outcomes providing students with opportunities to engage with materials and course work. As customized materials, OER can be modified to use only the portions desired by instructors without having additional materials that are not covered by the course, but which may present distractions to students and potentially hinder their learning. These factors provide faculty with opportunities to enhance their course instruction and improve student learning.

Faculty reported pedagogical improvements because of OER adoption. Faculty perceived these materials as a way to improve their teaching (Belikov & Bodily, 2016; Coleman-Prisco, 2017; Fischer et al., 2020). This improvement is based in part on faculty rethinking their courses (Watson et al., 2017) and faculty teaching becoming more aligned with materials when using OER (Martin & Kimmons, 2020). The ability to develop content and repurpose it to fit the specific needs of the course is another way in which OER adoption can help to facilitate pedagogical improvements and an additional consideration when adopting (Delimont et al., 2016; Farrow et al., 2015; Fischer et al., 2020; Lantrip & Ray, 2020; Ozdemir & Hendricks, 2017). Fischer et al. (2020), for example, determined just over 16% of faculty respondents were willing to adopt OER because these materials are adaptable. Faculty reported OER use promoted reflection, fostered changes to instructional practices, and increased teacher self-efficacy (Chetna, 2021; Lantrip & Ray, 2020; Magro & Tabaei, 2020; Pitt, 2015; Tillinghast, 2021; Weller et al., 2015) by encouraging them to take greater ownership of their materials and courses, evaluate what specific materials are needed without being limited by the structure of commercial textbooks, and create additional materials and new assignments. OER provided faculty with opportunities for self-reflection and assessment (Chetna, 2021). Results of three studies indicated faculty experiment and innovate more when using these materials (Fischer et al., 2020; Lantrip & Ray, 2020; Pitt, 2015) leading to changes in course structure and increased technology use in the classroom. In one study, 59% of faculty reported that they used OER because they allowed them to be more innovative with their teaching (Lantrip & Ray, 2020). In other studies, faculty believed changes made by implementing OER encouraged students to engage more with the course leading them to be more prepared (Delimont et al., 2016; Lantrip & Ray, 2020; Magro & Tabaei, 2020; Ozdemir & Hendricks, 2017; Pitt, 2015; Weller et al., 2015). For example, the majority of faculty believed that OER use improved student engagement (Weller et al, 2015). Adapting materials to align with course objectives and individual instructional practices can lead to an enhanced sense of ownership with the materials and the course, increasing faculty enthusiasm, motivation, and engagement with the course and encouraging students to further engage with the instructor, the course, and the materials.

The review of studies indicated students were more engaged with their courses when using OER. In six studies, students reported that OER made learning more fun thus prompting engagement with their courses and their instructors (Collins et al., 2020; Cooney, 2017; Gil et al., 2013; Ikahihifo et al., 2017; Vollman, 2021; Weller et al., 2015). Collins et al. (2020) examined the impact of OER use on student outcomes and perceptions and determined students believed using OER increased their course participation, improved their engagement, and promoted academic interest. Engagement is not defined in these studies and the interpretation is left to respondents. As a result, these responses should be viewed cautiously. One possible explanation for increased engagement is that students have the required materials and are better prepared to participate in the course. An additional explanation for these perceptions is the interactive nature of these materials, allowing for more directed learning and user interactions. OER can be edited and adapted to include relevant videos and links to additional resources that students can explore on their own to gain further information on course topics. As digital resources, these materials are easier to adapt and edit than commercial materials. Their licensing structure allows authors to edit existing materials to directly embed additional resources within them allowing students to interact with a cohesive instructional material instead of the multiple resources that are required under commercial copyright.

Additional explanations for increased student engagement included the variety of materials, which provide a broader perspective on topics (Choi & Carpenter, 2017; Feldstein et al., 2012) and the ability for materials to be tailored to the course allowing relevance to be more obvious to students (Fine & Read, 2020; Ikahihifo et al., 2017; Jaggars et al., 2018; Ozdemir & Hendricks, 2017). Survey responses about an OER created for a human factors and ergonomics course indicated students believed the OER provided them with more variety of perspectives than those provided in a commercial textbook (Choi & Carpenter, 2017) while results from another survey found 63% of students believed that the OER they used were more relevant than commercial materials (Jaggars et al., 2018). OER that are tailored to courses and the local environments in which students live can enable students to make more personal connections with their courses and course materials. These materials enable faculty to embed information more easily on how a topic is relevant to students’ communities and tailor the information to local environments without having to provide additional materials. Fialkowski et al. (2020), for example, adapted their OER to include a section on the nutritional needs of adults living in their local community. Adaptation and personalization provide an enriched learning environment that motivates students to engage with the materials and explore on their own. OER that are tailored to courses and learning environments can enable students to make a more personal connection with their courses and course materials, providing an enriched learning environment that motivates students to engage with the materials and explore on their own. This adaptation to fit local learning environments can increase student learning and improve academic outcomes by increasing students’ interest in course topics and motivation.

Academic Outcomes

Forty-five studies examined the impact of OER on academic outcomes. As seen in Tables 1 and 2, these studies used experimental, quasi-experimental, or case study designs and consisted of sample sizes ranging from n = 28 to n = 45,237. Studies evaluated the impact of OER on academic achievement using several different measures such as course grades, exam grades, completion and DFW rates, course throughput rate, and non-course specific measures. Studies will be discussed using their primary student outcome measurement.

Course Grades

Seventy-one percent of efficacy studies examined the impact of OER on final course grade. Results from 19 studies (59%) indicated no difference in final course grades between students using OER and commercial materials while results of 11 studies determined students using OER earned higher grades than students using commercial materials. For example, Baker and Sibona (2020) examined the impact of using an OER on performance in an information systems course and found that course grades increased with OER. Findings from the remaining two studies proposed student performance using OER was influenced by demographic characteristics such as student age and race. OER improved course grades for traditionally aged students but had no impact on older students (Clinton-Lisell, 2022). In addition, OER positively impacted final course grades for Latino students but negatively impacted Black students’ course grades (Dempsey, 2021). In addition to these trends, three studies analyzed the impact of OER on grade distribution and concluded OER use resulted in more A’s and B’s (Chang, 2020; Collins et al., 2020; Ryan & Nawalaniec, 2021). While failure rate remained the same, the percentage of students earning an A or a B increased to 66.6% of students compared to 33.3% and 37.6% of students using commercial materials (Ryan & Nawalaniec, 2021). OER provide students with access to materials from the start of the semester and this factor could potentially increase the number of students with needed materials resulting in a decrease in grade distribution and more students earning higher grades. Grade distribution affects course grades as more A’s and B’s result in a higher average overall course grade. The impact that early access has on course grades is mirrored in the impact OER use has on exam grades.

Exam Grades

Fifteen studies, including eight that discussed final course grades, examined the impact of OER on subject exam grades. Students performed the same when using OER as when using commercial textbooks in six studies while in four studies, students performed better when using OER. In a simple random experiment comparing OER use to commercial textbooks, students earned similar final exam grades (Bol et al., 2021). In one study (Delgado et al., 2019), students performed worse when using OER. In the remaining four studies, the impact of OER on exam scores varied (Allen et al., 2015; Choi & Carpenter, 2017; Kalaf-Hughes, 2019; Kersey, 2019a). Choi and Carpenter (2017) concluded differences in exam grades were short-lived and only occurred the semester OER was implemented. This was possibly due to alignment between exam questions and course materials as Choi and Carpenter (2017) used the same test bank with OER as was used with the commercial textbook. In three studies, the difference in performance between students using OER and commercial materials was based on the timing of the exam (Allen et al., 2015; Kalaf-Hughes, 2019; Kersey, 2019a). Students using OER performed worse on the first exam but similarly on later tests as students gained familiarity with the OER’s structure (Allen et al., 2015). Students performed better using OER on the first test while they performed worse on the midterm or final exam (Kalaf-Hughes, 2019; Kersey, 2019a). Earlier performance gains may be the result of earlier access to the materials and these results level out as the semester progresses and more students acquire commercial materials. The impact that early access to materials has on academic outcomes is more clearly seen in the effect OER has on completion and DFW rates.

Completion and DFW Rates

Sixteen studies examined student completion rates, withdrawal rates, or DFW rates which are a combination of drop, failure, and withdrawal. Eight studies examined student completion rates and determined they increased or remained the same when using OER. For example, Gil et al. (2013) examined the impact of using an OER in a computer science course and verified that students were less likely to drop the course after OER implementation. In two studies, OER reduced the drop rates (Bol et al., 2021; Wiley et al., 2016) while another four studies examined withdrawal rates, measured as students who earned a W grade on their transcript (Clinton-Lisell, 2022; Delgado et al., 2019; Dempsey, 2021; Vander Waal Mills et al., 2019). Only Dempsey (2021) concluded withdrawal rate increased in courses using OER which may be the result of students needing to access the OER through their course learning management system. Withdrawal rates decreased (Delgado et al., 2019) or were stable (Clinton-Lisell, 2022; Vander Waal Mills et al., 2019) in the remaining studies. DFW rates are reduced (Colvard et al., 2018; Croteau, 2017; Feldstein et al., 2012) or remain the same (Winitzky-Stephens & Pickavance, 2017) when using OER. In general, students are less likely to drop, fail, or withdraw from a course that uses an OER.

One possible explanation for course retention is students have the materials they need to be successful, and their success is not hindered by an inability to purchase required materials. According to Grimaldi et al.’s (2019) access hypothesis which stated that OER will be more beneficial for students who would not otherwise have the material, these results should be more pronounced for low-income students. While Colvard et al. (2018) did not control for student purchase of materials, they observed this result and found that DFW rates decreased more substantially for low-income students. This explanation is further supported by student survey results indicating that students withdraw or drop courses because of material cost.

Course Throughput Rate

The course throughput rate is a combination of drop rate, withdrawal rate, and grades of C or better in a course (Hilton et al., 2016). Only one study (Hilton et al., 2016) examined the impact of OER on this measure of academic outcome. As such, no further analysis of this topic was conducted.

Non-course Specific Measurements

Only three reports (Gurung, 2017; Hardin et al., 2019; Stovall et al., 2019) analyzed the impact of OER on non-course specific measurements such as standardized tests and department assessments. Given the lack of studies on this topic, no further analysis was conducted.

Research Methodologies and Limitations

As seen in Tables 1 and 2, most studies used quantitative research methods. Twenty-nine percent of reports were quasi-experimental studies, 16% were case studies conducted within a classroom, and another 3% were experimental studies, including two studies on student perceptions of OER. Just over a third (36%) of studies used surveys, including many of the studies examining barriers and incentives to OER adoption and use. While some of these surveys used open-ended questions, many of them relied on Likert-scale responses such as preference for print materials. Only 15% of studies primarily used qualitative or mixed methods in analyzing findings. As a result of these methodological designs, observed limitations primarily focus on quantitative studies.

Perception studies are impacted by several limitations, including reliance on self-report and not controlling for confounding variables. This reliance on self-reported responses may be impacted by self-selection bias which is tenable because these studies rely on convenience samples or those who already use OER. Jung et al. (2017) and Ozdemir & Hendricks (2017), for example, examined the perceptions of faculty users of OpenStax materials and the Cool4Ed repository. OpenStax is a publisher of open-access, peer-reviewed textbooks while Cool4Ed is a California state run repository of OER. Faculty perception studies do not typically control for faculty awareness and use of OER when examining their perceptions of these materials. Faculty awareness and adoption of OER may be a confounding variable when examining faculty perceptions, especially those of quality as it is unlikely that faculty would continue to use materials that they believe to be of low quality. Bliss et al. (2013a), Bliss et al. (2013b), and Coleman-Prisco (2017) evaluated the perceptions and experiences of faculty participating in a multi-institutional OER initiative. While Bliss et al., (2013a, 2013b) did not examine the perceptions of faculty who created these materials, it is unclear what influence familiarity with the author had on respondents’ perceptions. Faculty perception studies do not always identify faculty discipline or the level of courses they frequently teach. Given that OER are not found equally across all disciplines, this is an important confounding variable that should be examined to clarify perception studies. Student perception studies do not examine why students rate materials the way they do and do not provide information on what is being compared. Student rates may be indicative of their interest in the subject matter rather than a comparison of the materials used in their courses. Similar issues are found in the design of efficacy studies.

Causal conclusions require an established correlation between two variables, that one variable occur prior to the second variable, and that alternative plausible explanations have been eliminated. OER research does not typically meet these requirements, thus conducting a meta-analysis was not justified. While some studies show a correlation between OER and academic outcomes and examinations occur after OER have been introduced, none of the studies discussed offered alternative explanations such as alignment between course materials and exams, changes to instructional practices, or prior academic achievement.

Studies on the impact of OER on academic outcomes are limited by a failure to control for confounding variables. While 20 studies controlled for instructor variables by using data from courses taught by the same instructor, the degree to which changes were made varied and is often unclear. Observed results could be attributed to changes in instructional method in addition to or instead of material type. Even in instances where instructional practices were similar, OER was implemented in a later semester, and history and practice effects may account for perceived achievement growth over time (Shadish et al., 2002).

Adoption of OER can occur alongside other instructional changes. Finlayson (2020) used OER as part of an overall course redesign that implemented a flipped classroom approach. Lovett et al. (2008) adopted OER as part of the online redesign of their course. These redesigns may have impacted the results and changes in course performance could be attributed to these instructional changes rather than the use of OER. Nine studies, including three that controlled for instructor variables, controlled for student variables such as demographics or prior student achievement. Most studies examined student demographics or study time but did not consider academic achievement and its influence on future academic success. Sixteen studies did not control for any confounding variables. These cofounding variables, including prior academic achievement and changes made to instruction because of adopting OER, may provide alternative and plausible explanations for changes in outcomes between students using OER and those using commercial materials.

Studies do not always report effect sizes for observed results. As indicated in Table 1, only 13 studies reported an effect size. Most of these studies reported a small effect size for observed differences (Cohen, 1992). Failure to report an effect size limits interpretation of the practical significance of reported differences. These limitations should be addressed in future research with design recommendations advanced in a later section.

Discussion

In the previous section, we discussed the results of a systematic review of 97 studies describing OER research on student and faculty perceptions, barriers and incentives to adoption and use, and the impact of OER use on academic outcomes. This review extends previous research by conducting a systematic review using the PRISMA 2020 guidelines, examining incentives and barriers to OER adoption and use, disaggregating academic outcomes, and using self-determination theory as a framework to explain five main conclusions that emerge from this review.

First, OER increases student course engagement and promotes academic interest. OER that are adapted to students’ learning environments make material relevancy clearer and as a result can provide support for fulfilling students’ psychological needs for relatedness. By clearly connecting course materials to students’ lived experiences, OER help students to see how course information is directly related to their lives. Relevance can promote a feeling of relatedness not only to course materials but to the communities where students live by connecting course knowledge to students’ localities. Finlayson (2020) added a component to their OER that addressed the nutritional needs of individuals living in the area around their university providing students with a direct connection to how their coursework applied to their local environments.

In addition to directly connecting to local communities by providing local examples, OER can promote relatedness for students by involving them in OER development. Student involvement in OER development can not only promote their subject matter knowledge but also increase their feelings of belongingness in the academic community. Involving students in this way can help inform students about academic writing conventions and incorporates them into the academic community through the creation of a resource that is available for others to use in their classrooms, research, or other professional work. For example, Stovall et al. (2019) included students in the writing process of an OER for forestry studies that could be used by professionals in forestry management, potentially increasing students’ sense of belonging in their course, their university, and as professionals within their chosen field. In addition, student involvement in OER provides support for feelings of competency. In the same study, more students volunteered to write OER chapters after seeing student-written chapters published and Stovall et al. (2019) proposed that these students wanted to contribute to their peers learning and be recognized for this work. An additional explanation for this finding is that students’ sense of competency increased by seeing other students’ involvement in OER development.

Second, OER promote faculty innovation and create a greater sense of ownership of courses and course materials. As adaptable materials, OER provide opportunities for faculty to make them their own and to share their creations with one another. This ownership characteristic of OER provides support for instructors’ psychological needs of autonomy and relatedness. By providing faculty with opportunities to make materials their own and create learning materials that best fit their visions for the course, OER support faculty autonomy within their classes. Commercial materials are limited in their adaptability due to their licensing structures. While faculty have autonomy to choose their course materials and can use portions of multiple resources, OER provide faculty with options for editing and adapting materials to create cohesive course material that fits their needs.

In addition, the ability for faculty to share these materials and build on one another’s innovations supports relatedness by promoting connections with colleagues and creating a network of individuals working together to create, adapt, and promote OER use. Commercial materials are limited in their ability to be shared for adaptation due to their copyright structures. While faculty can co-author commercial materials or recommend these materials to one another, OER provide opportunities for faculty to create materials more collaboratively by building on each other’s work in a way that is not limited by copyright.

Third, despite the positive influence on autonomy and relatedness, faculty are hesitant to adopt OER due to the time constraints associated with it. Faculty reluctance to adopt OER is often the result of competing obligations resulting in faculty having to make a value judgement on the best use of their time. In some cases, faculty do not feel qualified or competent to find and adapt appropriate OER for their courses. In these situations, OER adaptation inhibits instructors’ psychological needs of competence due to self-doubt and a lack of self-efficacy in effectively incorporating these materials while in others faculty are reluctant to use these materials because their institutions do not provide support for OER and do not acknowledge work in this field as research and scholarship. In this case, it is not that faculty feel unqualified to adapt these materials but rather that faculty believe that the cost associated with finding and adapting OER is not worth the effort required to successfully complete this task. This lack of return on invested time is more prominent in institutions that do not include OER scholarship as part of the promotion and tenure process as faculty will “prioritize elements of their jobs that they will be evaluated for” (Martin & Kimmons, 2020, p. 140).

Fourth, almost 47% of studies examining the impact of OER on student academic achievement found that there was no difference between using these resources and using commercial materials. This finding is revealing not because OER did not improve student outcomes but rather because they do not harm them. A lack of improvement in student grades does not mean that OER should be dismissed but rather illustrates the other affordances of OER. From a purely economic perspective, outcome results remaining steady provide support for OER adoption as the cost-savings alone provide student advantages. Additionally, OER adoption is further supported from a motivation and learning standpoint. As indicated earlier, OER promote student engagement, increased subject-matter interest, and improved perspectives toward learning. Absent a direct negative impact on student outcomes, OER use may serve to promote greater lifelong learning and persistence by promoting students’ connections to academia and knowledge acquisition.

Finally, two academic outcomes that see improvement with OER use are DFW rates and grade distributions. Students using OER are less likely to withdraw from a course. In addition, courses using OER have a narrower grade distribution with more students earning higher grades. This finding was not seen in previous reviews which examined academic outcomes wholistically and potentially underestimated OER’s impact on grade distribution as a result. While OER may not drastically change student outcomes on a statistically significant scale, these findings are promising for promoting equity. The impact of OER on grade distribution and DFW rates may be the result of increased student access to course materials further increasing inclusivity and promoting relatedness. In addition, use of OER eliminates lack of course materials as an academic barrier to success which in turn can provide support for students’ feelings of competence and lead to better academic outcomes.

Limitations

There are several limitations to this review. First, the review was limited to articles that were published in peer-reviewed journals. This may have introduced a publication bias in the results. Publication bias is the result of included studies not systematically representing all studies that could have been included (Banks et al., 2012). Bias can be introduced by excluding gray literature due to what Rosenthal (1979) calls the “file drawer problem.” This common publication bias is due to an emphasis on publishing studies with large samples and statistically significant results (Banks et al., 2012). While we excluded gray literature and relied on peer-reviewed journals, it is encouraging that 46.67% of efficacy studies reported non-significant findings. In addition, 24.7% of all studies had fewer than 100 participants while 42% of studies had fewer than 200 participants.

The review was focused on postsecondary education and may not generalize to OER in other settings such as the K-12 system or corporate and non-formal learning environments. In addition, most studies (n = 79) were conducted in the USA. Of the remaining 18 studies, seven were conducted in either the UK or Canada. Eight studies included participants from across the globe, but most participants were in the USA, UK, or Canada. In addition to the focus on North American and European contexts, most studies were limited to English-speaking participants. As a result, it is unclear to what degree these findings are generalizable to countries outside of North America and Europe.

This review was limited to studies published in English. Arinto et al. (2017) argued that this is a general limitation of OER as most available resources are in English. The exclusion of non-English studies may have excluded studies from non-English speaking countries. Whether the predominance of the USA as a study location is a factor of excluding non-English studies or a factor of the state of OER research is unclear. Future research should address this issue to ensure generalizability of findings to non-Anglosphere countries.

Implications and Future Research

Despite the limitations of existing studies and the need for future research, existing scholarship on OER has pedagogical and practical implications for faculty, university and college administrators, and researchers. These implications provide a framework for effectively incorporating OER into courses, creating and implementing OER initiatives, and furthering OER research.

From a pedagogical perspective, the effective use of OER involves more than just adopting them. A distinguishing feature of these materials is the ability to adapt and modify them to align with course goals and student learning outcomes. Materials can be adjusted to fit local environmental factors and needs. Fialkowski et al. (2020), for example, created an OER that examined the nutritional needs of their local population while Stovall et al. (2019) added a section to their OER that addressed local environmental factors in forestry studies. This adaptability provides opportunities for students to make more personal connections to the materials and connects the classroom to the local environment in which students live. Faculty wanting to adopt OER are encouraged to customize these materials and adapt them to their classroom and university environments. This adaptation process is time-consuming and often requires expertise in technology and copyright laws that faculty may lack. It is recommended that faculty interested in adapting and creating OER seek out technological and copyright experts to assist them. Faculty can also involve their students in the creation of OER.

Student involvement in OER can benefit students academically and has implications for universities and policymakers. Students interested in OER are encouraged to work with instructors to create and adapt these resources. This involvement could involve independent study or research projects that provide students with direct experience in their disciplines. Students can also become involved in OER policies by joining student public interest groups such as the Student PIRG, Open Textbook Alliance, that advocates for the use of these resources. By working directly with higher education faculty and staff, student advocacy has direct applications to the practical implications of OER scholarship.

OER research provides a framework for university and college administrators wanting to promote these resources. The adaptation and adoption process are time-prohibitive for many faculty, especially in institutions that do not provide support for OER initiatives. Institutions wanting to promote these resources should provide direct support for faculty, including technical and copyright expertise, general support staff, and financial incentives to encourage their use. A well-developed university initiative would involve faculty, staff, and administrators from across university offices and ensure faculty recognition. Universities are encouraged to include OER as scholarship and consider authorship of these materials in promotion and tenure criteria. Initiatives providing institutional support for OER will create a culture where faculty are motivated to adopt and adapt these resources. A university culture that supports these materials can help further research on this topic.

Future OER research should address the limitations of existing studies. Perception studies would benefit from clearer definitions of quality or follow-up questions about what factors respondents used in making their determination. Factors external to the materials including frequency of use and subject matter interest could impact student ratings of these materials. Faculty perception studies would benefit from including a wider range of faculty, including those who are not currently using OER. These studies should also examine the correlation between the adoption of OER and the perceptions of the OER quality among faculty. Future research on faculty perceptions of OER limited to those who have adopted them should add questions regarding OER usage. Questions on adaptation rather than just adoption will help to better address the potential benefits of OER and better capture the possibilities afforded by their licensing structure. Impending research should address questions of faculty engagement with the adaptation process such as: What adaptations do faculty make to adopted OER? How does OER adoption impact faculty engagement with their courses? In what ways has course structure changed as a result of OER adoption?

Studies examining academic outcomes should control for confounding variables such as the impact of possible instructional change and student prior academic achievement. Instructional change has the potential to confound the results of OER studies as it is possible that what is being measured is not the impact of OER but rather the impact of closer alignment between teaching and instructional goals or changes in student/teacher relationships. Research should include a wider range of courses, especially those at the upper and graduate levels to improve the generalizability of results. Further information is needed on these populations to determine what impact, if any, OER has on student outcomes beyond the introductory level.

OER research should include longitudinal studies. Results of existing studies indicated that students are less likely to withdraw or drop courses that use OER than those that use commercial textbooks. Understanding the relationship between OER and student retention is an important area for future research. Impending research should seek to address the following questions to clarify the impact of OER on academic outcomes: What impact does the use of OER have on 4-year graduation rates? What impact does the use of OER have on retention at the university level? What impact does the use of OER have on academic course achievement in later courses, including the transfer of skills? These questions and others will enhance OER research beyond the impacts of academics within a single course which might be an effect of instructional method.

Conclusions

Governments and higher education institutions are concerned with rising educational costs and promote the use of cost saving initiatives designed to reduce fees and expand educational access. OER are one of the methods used to achieve these goals. Given external pressures to adopt these materials, it is important to understand how they are perceived by faculty and students and what impact they have on academic outcomes.

Based on a systematic review of the literature, faculty and students viewed these materials positively. In addition, students using OER performed no worse than those using commercial materials and are less likely to withdraw from courses. While these outcomes are encouraging in terms of academic achievement, initiatives designed to promote OER should be implemented with careful consideration. Faculty face many barriers to adopting these materials, including many that are beyond their control. Ensuring that faculty have necessary support such as technological and copyright expertise and recognition is an essential component of creating OER initiatives at the institutional level. These findings and the fact that many students do not purchase course materials due to cost emphasize the need to explore alternatives to costly instructional materials. OER provide one alternative that increases access to education and academically and financially serves the needs of students.