Gunilla Derefeldt

Colour concept retrieval by free colour naming. Identification of up to 30 colours without training

Abstract Recent neuroscientific findings concerning the relationship between the perceptive, cognitive and linguistic aspects of colour suggest that colour concept retrieval would be enhanced by free colour naming or by the use of natural associations between colour concepts and colour words. To test this hypothesis, we had subjects give their own free associations to a set of 35 colours presented on a display. The results suggest that subjects with normal colour vision are able to identify absolutely 30 colours or more without training if colours are well separated, basic colours are used and colour concepts and colour words are naturally associated.

Cognitive aspects of color

This report surveys cognitive aspects of color in terms of behavioral, neuropsychological, and neurophysiological data. Color is usually defined as psychophysical color or as perceived color. Behavioral data on categorical color perception, absolute judgement of colors, color coding, visual search, and visual awareness refer to the more cognitive aspects of color. These are of major importance in visual synthesis and spatial organization, as already shown by the Gestalt psychologists. Neuropsychological and neurophysiological findings provide evidence for an interrelation between cognitive color and spatial organization. Color also enhances planning strategies, as has been shown by studies on color and eye movements. Memory colors and the color- language connections in the brain also belong among the cognitive aspects of color.

Visualization of VDU colours by means of the CIELUV colour space

The CIE 1976 (L∗ u∗ v∗) system, abbreviated CIELUV, has been widely used for specification of colours, for specification of colour differences, and for selection of colours presented on CRT screens. However, VDU colours have not earlier been visually presented as a virtual colour atlas with coloured patches occupying the appropriate positions in the CIELUV colour space. In this paper, CIELUV is illustrated by displaying the colours of 4 096 digital RGB combinations in chroma (C∗uv) — lightness (L∗) diagrams at five-degree increments in hue angle (huv) around the entire CIELUV hue circle. The 4 096 colours are quite nonuniformly distributed in the space. In particular, some yellows, blue-greens, and oranges are completely inaccessible by the VDU because of sparse sampling. Thus sampling, as well as gamut constraints, limit the colours accessible on a VDU.

Transformation of NCS data into CIELUV colour space

The CIE (L∗, u∗, v∗) system, abbreviated CIELUV, and the Swedish Natural Colour System (NCS) have been compared. The data for the NCS was transformed to CIELUV; the transformation involved taking the CIE tristimulus values of the nominal NCS notations, i.e. the colorimetric aimpoints representing the NCS, converting these values to CIELUV and plotting them in the CIELUV space. All the data has been calculated using CIE standard illuminant C and the 1931 standard observer. Although the data shows that no simple linear relationship exists between the NCS and CIELUV systems, the systems may nevertheless be considered closely related. Of the existing colour order systems, i.e. NCS, Munsell etc., the NCS is closest to CIELUV. As NCS represents the perceptual and cognitive aspects of colour better than CIELUV, the NCS may be considered as highly appropriate for a descriptive specification of colours for VDUs.

NCS colour space for VDU colours

Abstract Perceptually based colour spaces, colour order systems and colour naming systems based on natural language categories are being increasingly applied to the specification of colour appearance of colour VDUs. Since the Natural Colour System (NCS) is defined according to fundamental attributes of colour perception and the NCS colour notations agree well with cognitive and linguistic aspects of colour, the NCS is very convenient for colour selection in human-computer interaction. However, VDU colours have not earlier been visually presented as a virtual NCS colour atlas with coloured patches occupying the appropriate positions in the NCS colour space. In this paper, the NCS is illustrated by displaying the colour stimuli of 4 096 digital RGB combinations into NCS colour triangles representing 80 different NCS hues.

How to identify up to 30 colors without training: color concept retrieval by free color naming

Used as a redundant code, color is shown to be advantageous in visual search tasks. It enhances attention, detection, and recall of information. Neuropsychological and neurophysiological findings have shown color and spatial perception to be interrelated functions. Studies on eye movements show that colored symbols are easier to detect and that eye fixations are more correctly directed to color-coded symbols. Usually between 5 and 15 colors have been found useful in classification tasks, but this umber can be increased to between 20 to 30 by careful selection of colors, and by a subjects practice with the identification task and familiarity with the particular colors. Recent neurophysiological findings concerning the language-concept connection in color suggest that color concept retrieval would be enhanced by free color naming or by the use of natural associations between color concepts and color words. To test this hypothesis, we had subjects give their own free associations to a set of 35 colors presented on a display. They were able to identify as many as 30 colors without training.