From spectral information to animal colour vision: experiments and concepts

Abstract

Many animals use the spectral distribution of light to guide behaviour, but whether they have colour vision has been debated for over a century. Our strong subjective experience of colour and the fact that human vision is the paradigm for colour science inevitably raises the question of how we compare with other species. This article outlines four grades of 'colour vision' that can be related to the behavioural uses of spectral information, and perhaps to the underlying mechanisms. In the first, even without an (image-forming) eye, simple organisms can compare photoreceptor signals to locate a desired light environment. At the next grade, chromatic mechanisms along with spatial vision guide innate preferences for objects such as food or mates; this is sometimes described as wavelength-specific behaviour. Here, we compare the capabilities of di-and trichromatic vision, and ask why some animals have more than three spectral types of receptors. Behaviours guided by innate preferences are then distinguished from a grade that allows learning, in part because the ability to learn an arbitrary colour is evidence for a neural representation of colour. The fourth grade concerns colour appearance rather than colour difference: for instance, the distinction between hue and saturation, and colour categorization. These higher-level phenomena are essential to human colour perception but poorly known in animals, and we suggest how they can be studied. Finally, we observe that awareness of colour and colour qualia cannot be easily tested in animals.

Nocturnal light environments and species ecology: implications for nocturnal color vision in forests

“…Nocturnal animals thus encounter changing visual environments at temporal and spatial scales, particularly in seasonally deciduous forests. Kelber and colleagues have recently argued that nocturnal color vision may be advantageous in changing light environments in some nocturnal vertebrates (Kelber et al, 2002;Kelber et al, 2003;Johnsen et al, 2006;Kelber and Roth, 2006;Kelber and Lind, 2010;Kelber and Osorio, 2010). Similar arguments for the selective advantage of using color vision rather than achromatic cues in conditions that exhibit great spatial and temporal fluctuations in intensity have been made for terrestrial (Mollon, 1989) and aquatic forests (Cummings, 2004) in diurnal conditions.…”

Photoreception and vision in the ultraviolet

“…Many animals with UV photosensitivity, particularly invertebrates, have both wavelength-specific behaviors and color vision (Menzel, 1979; see also Kelber and Osorio, 2010).…”

Visual acuity trade-offs and microhabitat driven adaptation of searching behaviour in psyllids (Hemiptera: Psylloidea: Aphalaridae)

“…Hence, the capacity of the psyllid's visual system to detect host leaves relies on its perception of leaf colours and its ability to resolve objects in natural conditions. Colour vision is the perception and discrimination of light wavelength radiation independently from intensity (Kelber and Osorio, 2010). The basic requirements to demonstrate colour vision in an organism include the presence of at least two classes of photoreceptor of varying spectral sensitivity, behavioural evidence for intensityindependent colour discrimination and evidence of the ability to process different spectra inputs via colour opponency mechanisms (Kelber and Osorio, 2010;Kemp et al, 2015).…”

“…Colour vision is the perception and discrimination of light wavelength radiation independently from intensity (Kelber and Osorio, 2010). The basic requirements to demonstrate colour vision in an organism include the presence of at least two classes of photoreceptor of varying spectral sensitivity, behavioural evidence for intensityindependent colour discrimination and evidence of the ability to process different spectra inputs via colour opponency mechanisms (Kelber and Osorio, 2010;Kemp et al, 2015). Considering colour vision has, to date, only been conclusively demonstrated for a limited number of vertebrate and invertebrate model organisms, a framework was recently presented for contributions pertaining to the possible existence of colour perception in new taxa for which not all information currently exists to definitely prove colour vision (Kemp et al, 2015).…”