Colour spaces in ecology and evolutionary biology

Abstract

The recognition that animals sense the world in a different way than we do has unlocked important lines of research in ecology and evolutionary biology. In practice, the subjective study of natural stimuli has been permitted by perceptual spaces, which are graphical models of how stimuli are perceived by a given animal. Because colour vision is arguably the best-known sensory modality in most animals, a diversity of colour spaces are now available to visual ecologists, ranging from generalist and basic models allowing rough but robust predictions on colour perception, to species-specific, more complex models giving accurate but context-dependent predictions. Selecting among these models is most often influenced by historical contingencies that have associated models to specific questions and organisms; however, these associations are not always optimal. The aim of this review is to provide visual ecologists with a critical perspective on how models of colour space are built, how well they perform and where their main limitations are with regard to their most frequent uses in ecology and evolutionary biology. We propose a classification of models based on their complexity, defined as whether and how they model the mechanisms of chromatic adaptation and receptor opponency, the nonlinear association between the stimulus and its perception, and whether or not models have been fitted to experimental data. Then, we review the effect of modelling these mechanisms on predictions of colour detection and discrimination, colour conspicuousness, colour diversity and diversification, and for comparing the perception of colour traits between distinct perceivers. While a few rules emerge (e.g. opponent log-linear models should be preferred when analysing very distinct colours), in general model parameters still have poorly known effects. Colour spaces have nonetheless permitted significant advances in ecology and evolutionary biology, and more progress is expected if ecologists compare results between models and perform behavioural experiments more routinely. Such an approach would further contribute to a better understanding of colour vision and its links to the behavioural ecology of animals. While visual ecology is essentially a transfer of knowledge from visual sciences to evolutionary ecology, we hope that the discipline will benefit both fields more evenly in the future.

Assessing Sexual Dicromatism: The Importance of Proper Parameterization in Tetrachromatic Visual Models

“…Is a color patch differing by 5 JNDs as discriminable from a reference as a patch differing by 7 JNDs? Following Fechner’s assumption of additivity, large colorspace should be possible to model (discussed in [95, 96] among others). Furthermore, the only study investigating a behavioral response (in this case the visual attention reflex) in relation to perceptually large color distances found that just-noticeable-differences, as calculated by the receptor noise model, are effective in describing colors separated by large distances in visual space [97].…”

Relative colour cues improve colour constancy in birds

“…We trained chickens to discriminate a rewarded orange (S+) from an unrewarded yellow (S2) in the control illumination (Renoult et al, 2015;. (C) Chromaticity diagram (VS, S, M and L indicate violet-, shortwavelength-, medium-wavelength-and longwavelength-sensitive cone types, respectively) of all stimuli in experiment 1, using the RNL model, for adaptation to the grey background under white illumination (grey circle).…”

Spaces in the Brain: From Neurons to Meanings

“…In other animal species, the psychological color space has only been investigated, via discrimination tasks, for a limited number of species (Renoult et al, 2015). However, the dimensionality of the space varies from one-dimensional (black-white) two-dimensional (in most mammals), three-dimensional (e.g., in primates), to four-dimensional (in some birds and fish).…”

“…A paradigmatic example is the color space (Vos, 2006; Renoult et al, 2015), but also, for example, the emotion space (Russell, 1980; Mehrabian, 1996) and musical space (Longuet-Higgins, 1976; Shepard, 1982; Large, 2010) have been extensively studied. Within cognitive linguistics, such spaces are also assumed to be carriers of meaning.…”

“…For example, it is rather well understood how the different types of cones and rods in the human retina result in the psychological color space (see Renoult et al, 2015 for a review). The mammalian brain sometimes represents space in topographic structures.…”