Working memory (WM) plays an important role in everyday visual behavior. Most studies that have examined visual WM have looked at the amount and quality of the information that can be stored the system (e.g. see Cowan, 2010 for a review). Bae and colleagues (2015) were among the first scientists to examine the content of information in visual WM. More specifically, they proposed a dual-content model of colour representation in which they argue for the importance of colour categories defined by commonly used terms (e.g. ‘red’, ‘blue’, ‘green’, etc.) in visual perception and WM. In their first set of experiments, they asked participants to name colours on a colour wheel containing 180 equally spaced colour hues and subsequently used categorization experiments with the most frequently mentioned colour names to define category boundaries. In a second set of experiments, they found that colour estimations drawn from memory are systematically biased away from the boundaries of the colour-term category towards the category centre. Their findings indicate that perceiving and reproducing a certain colour relies on both continuous hue estimations and on categorical representations of hue that correspond to the verbal terms they use to describe a colour. The findings of Bea and colleagues are appealing, because colour perception seems to have a strong categorical nature in human subjects. For example, English speakers feel comfortable using only 11 terms or less to describe colours, while they are able to distinguish up to 100.000 shades within each of these categories (Pointer & Attridge, 1997; Linhares, Pinto, & Nascimento, 2008). The dual nature of colour perception and WM that was proposed by Bae and colleagues is also supported by neuroscientific evidence, that shows that both continuous and categorical representations of colour can be found in human brains (Bird et al., 2014). Recent advancements in cognitive psychology and psychophysiology have shown that it is possible to infer the content of visual WM from pupil measurements (Mathôt, 2018). Olmos-Solis and colleagues (2016) conducted an experiment in which participants needed to store a colour in visual working memory. During the retention interval, they showed task-irrelevant probes that either matched or did not match the colour that was maintained in working memory. Olmos-Solis and colleagues showed that when a stimulus matches the content of visual WM, it triggers a stronger pupil constriction compared to stimuli that do not match the content of WM. This effect is mediated by the fact that stimuli that match the content of WM are likely to capture attention (Olivers, Meijer & Theeuwes, 2006), which is known to elicit a pupil response (Mathôt, 2018). In this research project, we aim to further explore the effects of verbal colour categories on colour perception, visual WM and colour reproduction by using pupillometry. This open science framework repository contains a project proposal and python-scripts for colour selction.
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