SUMMARY

The work for the report was initiated by CIE Division 1: Vision and Colour and was carried out in the Reportership R 1-11: "Cognitive Aspects of Colour", under the following terms of reference:

To report on the cognitive aspects of colour in terms of behavioural, neuropsychological, and neuro-physiological data. Cognitive aspects of colour are not given in the CIE definitions of psychophysical colour and perceived colour.

The final report from R 1-11 was published with the title "Cognitive Color" in Color Research and Application, 29(1), pp. 7-19. 2004. In this article, the concept of cognitive colour was discussed in relation to colour categorization, colour coding, colour naming, the Stroop effect, spatial organization of coloured visual objects, attention, visual search and colour memory.

The results show that there are aspects of colour that the CIE definitions of psychophysical and perceived colour do not cover, although it gives notes to some of them. These phenomena could be referred to as "cognitive colour" and they point to the need for a new formal definition of colour in the CIE terminology. It is recommended that the term "cognitive colour" be added to ILV.

Cognitive colour is very important in certain specific tasks. Some of these tasks are listed in Derefeldt et al.'s paper (Cognitive Color. Color Research and Application, 29(1), pp. 7-19, 2004). A common property of these tasks is the importance of the economy of cognition of the human brain. It means that perceived colours are represented and stored in a compressed form i.e. as "cognitive colours". This accelerates complex tasks like visual attention, visual search, figural organization, figural segregation, etc. This economy has probably been of great survival value. For these tasks, colour appearance models alone, including the calculations recommended for assessing colour appearance and colour differences, may be limited for predicting how an observer will behave in these complex tasks. We must define cognitive colours by the boundaries of a continuous perceived colour set, or by a "representative item" of this set, and assign a name to the cognitive colour. If the perceived colour changes, e.g. due to illumination change and colour inconstancy, then the cognitive colour may also change.

We must be able to describe whether the cognitive colour changes or not. We can provide some guidance on how to select colours that are "cognitively consistent". These "cognitively consistent" perceived colours may be the "representative items" mentioned above, e.g. the focal colours or the prototypical colours of familiar objects (skin, sky, grass, fruits, vegetables, natural objects like sand, soil, water). At the boundaries of the set of perceived colours, observers tend to disagree, see Boynton, R.M., Olson, C.X. Locating basic colours in the OSA space. Color Res. Appl., 12, pp. 94-105, 1987.

It is also recommended that the work carried out in TC 1-42 "Colour Appearance in Peripheral Vision", in TC 1-61: "Categorical Colour Identification" and TC 1-65: "Visual Appearance Measurement", all of them representing interesting aspects of cognitive colour, should incorporate the findings and conclusions from this report. The results presented in "Cognitive Colour" should also be of significance for the work carried out on electronic imaging within Division 8: Image Technology.

Finally, it is recommended that work on the "emotional aspects of colour" be initiated. Emotions and feelings are related to both the cognitive and perceptual aspects of colour but the emotional aspects of colour are not addressed within any TC within CIE Division 1. Emotions and feelings are important aspects of how colour and light affect human expectations, motivations, and performance.