Abstract
Goodhew et al. (Attention Perception & Psychophysics, 79, 1147–1164, 2017) claim we (Skottun & Skoyles) hold: (1) that it is not possible to separate contributions from the magno- and parvocellular systems to psychophysical tasks, and (2) that there are no differences between magno- and parvocellular cells. Neither of these claims is correct.
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Goodhew and colleagues (2017) make the following two claims: (1) That we (Skottun and Skoyles) hold that contributions from the magno- and parvocellular systems cannot be differentiated in psychophysical experiments. However, the situation is the opposite: As we have repeatedly pointed out, such differentiation can be obtained by testing contrast sensitivity to high versus low spatial frequencies (Skottun, 2000, 2015; Skottun & Skoyles, 2007). (2) That we hold that there are no differences between magno- and parvocellular cells. As we have also pointed out on numerous occasions (Skottun, 2000, 2013, 2014, 2016; Skottun & Skoyles, 2007) such differences do exist. Thus, both claims by Goodhew et al. (2017) are incorrect. What we have done is to point out difficulties using suprathreshold stimuli (i.e., at contrast levels above threshold) to differentiate contributions from the magno- and parvocellular systems to psychophysical tasks. Based on reviews of the literature and quantitatve analyses, we have found such difficulties in connection with tasks based on contrast-response functions (Skottun, 2014), spatial frequency (Skottun, 2015), and temporal frequency (Skottun, 2013, 2016). Quantitative analyses also indicate that it is difficult to use visual persistence/temporal gap detection to assess magnocellular contributions because the stimuli used in such tasks have their largest amplitudes at the very lowest temporal frequencies (Skottun, 2004; Skottun & Skoyles, 2008).
References
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Skottun, B.C., Skoyles, J.R. On separating the magnocellular from the parvocellular: Responses to two statements by Goodhew et al.. Atten Percept Psychophys 79, 2233 (2017). https://doi.org/10.3758/s13414-017-1386-6
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DOI: https://doi.org/10.3758/s13414-017-1386-6