Keywords

1 Introduction

Photos and other images are quite simple and efficient tool to be used for induction where are proposed as stimuli for experimental psychology [1]. On the other hand the use of personal image provided directly by the participants to the experiment are very rare. One of the main problems that makes personal images not so used is that they are not able to be standard, by definition.

As empirical based science, psychology need to use standard tests that can be replicated and so used also for other studies [2]. However the chance to use personalized stimuli can be a catalyst for new ideas and indeed keen empirical science.

Personalized stimuli can be used, for example for working with episodic memory pushing both cognitive psychology and emotional science [3].

1.1 Toward an Integrated Approach

Since we used a personalized tool, the experimental complexity increased a lot and the risk of biases was to be taken into serious consideration.

Even if standardization of experimental stimuli remains in our opinion very crucial, there are different situations or studies, in both clinical and experimental settings, in which the enrichment of personal cues might be crucial and keen. The role of emotions and episodic memory, might be related to personal images in a very strong way [4]. Potentially these aspects could be driver of our behavior already in focus attentional process and so having an impact in decision making processes and other outcome of consequent actions [5].

Our hypothesis, in this study, was to find a preliminary evidence of a relationship between personal images and focused attention measured with eye-tracking, being this an objective and reliable instrument to catch such a sensible and fast construct such as the attention.

Moreover, we hypothesized that some personality traits were able to affect this relationship, and in particular we considered that more introvert people was prone to focus more on personal image, being them more focused on their own sphere than the social one.

2 Materials and Methods

2.1 Participants

Twenty-three students (19 females) attended the Faculty of Psychology at the Catholic University of Sacred Heart of Milan, Italy, and took part in the experiment. All the participants were students, also in psychology or communication, but without previous knowledge of eye-tracking and in particular with no knowledge of the attentional processes investigated in the experiment. Social, economic, cultural and historical background were all similar since all the participants were student in the same University and with similar background. They were first met by one of the researchers during academic courses or through personal contacts and then contacted via mail and/or telephone to schedule a meeting at the laboratory where the eye-tracker were installed. The topics associated with the experiment were not mentioned during academic courses or personally.

Two of the participants failed to complete the experimental session due to personal or technical problems and were excluded from statistical analyses. The final sample was composed of 21 students, who were assessed with the TIPI personality test [6] to be considered more or less introverts or extroverts.

2.2 Procedure

Participants where contacted months before of the experimental session and were required to provide soon after 30 personal photos mixing people and places. Xx of these photos were selected by a psychology researcher to be comparable with the neutral photos. An analysis of perceptive salience of all the photos has been done by using Matlab, in order to endure that all the stimuli were not able to grab the attention due to perceptive processes.

Researchers then created specific algorithms to include all the photos of each participants in the pipeline to be be presented to each subject as her/his own personal stimulus but mixed with the neutral photos.

Once in the laboratory the day of the experiment, the participants were required to fulfill some questionnaires. In particular the TAS-20 for alexitimia [7]; State Traits Anxiety Inventory, STAI-Y [8]; TIPI for personality [6]; and finally the Self Assessment Manikin SAM [9], for evaluating perceived level of physiological arousal, emotional valence, and dominance.

At this point the experimental task started. The participants were required to watch the monitor in front of them, staying still, while the head position was kept through an opportune hardware support for the chin. The photos were showed from the custom algorithm while the eye-movements were tracked at the same time.

2.3 Signal Acquisition and Data Analysis

The experiment was carried out in the labs, equipped with two portable PCs, one for delivering the stimuli and the other for acquiring eye-tracker data.

The pupillometry data were acquired using an Eye-link 1000, including experimental design software to record all raw signals, then exported and resampled at 1000 Hz.

In our study, by using the eye-tracker data extraction, we obtained for each participant a matrix of gaze and pupil data corresponding to each stimuli presentation (all the personal and neutral photos); in particular, we collected 1000 rows for each second (sampling to 1000 Hz), thereby making it possible to establish the exact period of each stimulus in the pipeline.

The software for the eye tracker was programmed to process the eye-movement indicators in terms of the number of fixations and saccades, that quantify the level of attention spent in each photo.

3 Results

Results have been highlighted following. In particular, we reported the descriptive statistics for both the questionnaires (Table 1) and for eye-tracking indexes (Table 2).

Table 1. Descriptive statistics for questionnaires
Full size table
Table 2. Descriptive statistics for eye-tracking indexes
Full size table

Within, between and interaction effects are highlighted in a 2 × 2 mixed experimental design with the within condition (Personal vs. Neutral) by the between condition TP score (extroverts vs. introverts) (Table 3).

Table 3. Univariated tests for eye-tracking indexes
Full size table

Results showed that personal images have in general higher number of fixation and more saccades (Fig. 1). This means that participants were more prone to focus to personal images than neutral, but this was of course expected, being the photo personal. Indeed, the interesting result is the different attentional levels of introverts and extroverts. In fact, while extroverts showed no differences in exploring personal and neutral photos, introverts participants showed an higher number of fixations and more saccades for personal images than neutral (Table 2 and Fig. 1).

Fig. 1.
figure 1

Fixation and saccades in both personal and neutral photos for both introverts and extroverts.

Full size image

This indicates that the difference between personal and neutral images is mostly due to the contribution of introverts that tends to focus significantly more than extroverts when they focus on personal images than neutral.

4 Discussion

With this preliminary study we were interested in understanding (1) if personal images were related to attentional processes, and (2) if personality traits, and in particular more introvert people, were more focused on their own personal images that others.

Results showed that the relationship between personal images and attentional processes is crucial, but the extend to which this can be considered so strong to have an effect is still to be verified in further studies.

On the other hand, we faced statistical differences in the attention that introverts dedicated to personal images, where extroverts showed no differences. The results are still too preliminary to draft any conclusions but the effects that, once verified, this could have on the field is really interesting and deserve to be discussed and explored in further works, even exploiting other aspects of personality and also focusing on the whole spectrum of the personality traits than in two opposite extreme.