2024 January Vision Meeting

2024 January Vision Meeting









We’re looking forward to seeing you for a packed schedule of great scientific talks in all things colour vision, including this years Palmer Lecture: “Animal Colour Vision,” given by Professor Daniel Osorio. Coffee, lunch, Halstead-Granville tea and post-meeting drinks and food all included with registration fees:
Member £40
Student Member £20
Non-member £60
Student Non-member £30

Why not renew or join our 2024 membership to benefit from the Member rates for this meeting?
Become a Colour Group (GB) member or renew your membership

2024 January Vision Meeting will be held at:
Drysdale Building (lower ground floor)
City, University of London
Room ELG01
Northampton Square, London

Abstracts following programme

10:00 – Coffee and Registration

10:20 – Welcome & Tribute to Sophie Wuerger

10:35 – Chromatic discrimination for stimuli of different sizes
Marina Danilova University of Cambridge

11:05 – Re-examining the validity of the visual Mismatch Negativity (vMMN) as a measure of the categorical colour processing
Jasna Martinovic University of Edinburgh

11:35 – The relationship between waveguild cone photoreceptors and colour vision in patients with diabetes mellitus
Megan Vaughan Anglia Ruskin University

12:05 – Lunch

13:30 – Characterising the evolutionary relationship between colour visions and colouration in primates
Robert Macdonald University of Sheffield

14:00 – A journey through colour and space with good friends, food and wine

14:05 – Palmer Lecture: Animal Colour Vision
Daniel Osorio University of Sussex

15:00 – Halstead-Granville Tea

15:30 – The neural mechanisms underlying colour afterimages
Christoph Witzel University of Southampton

16:00 – The “super-importance of hue” in psychophysics, physiology and AI
Laysa Hedjar University of Giessen

16:30 – Chromatic Scene Statistics and Aesthetics
Anna Franklin University of Sussex

17:00 – Food and drink reception at The Pool (formerly AG19) at the College Building


Chromatic discrimination for stimuli of different sizes
Marina Danilova University of Cambridge

It is already known that chromatic discrimination deteriorates as the size of the stimulus is reduced.  However, in classical studies the observer was exposed for long periods to the chromaticity at which discrimination was measured and therefore the results for different chromaticities were obtained with the observer in different states of adaptation.  The results of such studies cannot be used to estimate human colour sensitivity in a constant state of adaptation.  In the present set of psychophysical experiments, discrimination ellipses were measured for several regions of the MacLeod-Boynton (1979) chromaticity diagram and for three different sizes of the stimulus, from 32 min to 2.4 deg in diameter.  The observers were constantly adapted to a metamer of D65 (standard CIE Daylight Illuminant); the stimulus duration was 100 ms to minimally disturb adaptation.  As in previous studies, the smallest thresholds were measured for larger stimuli.  In addition, however, in some parts of the chromaticity diagram, we observed rotation of the discrimination ellipses and transition from elliptical to more circular shapes as size changed.  Often the changes reflected a change in the relative thresholds for hue and for saturation.  These changes in the shape of discrimination ellipses with the size of the stimuli question current models of chromatic discrimination.

Supported by the Huawei Research project “Psychophysical studies of appearance models for color reproduction in scaled images”.

Re-examining the validity of the visual Mismatch Negativity (vMMN) as a measure of the categorical colour processing
Jasna Martinovic University of Edinburgh

Purpose: Although it is well known that photoreceptor damage and colour vision loss occur in patients with diabetes mellitus (DM), the relationship between these structural and functional changes remains unclear. By using highly sensitive measures of photoreceptor structure and function, we aim to determine whether early loss of colour sensitivity in DM is also accompanied by decreased cone density. Methods: Monocular data from 25 patients with DM, along with 25 controls, were examined to assess the integrity of their cone photoreceptors and their red/green (RG) and yellow/blue (YB) colour vision. Central cone density was assessed using confocal adaptive optics scanning light ophthalmoscopy and colour vision was assessed using the Colour Assessment and Diagnosis test. Results: Both RG and YB thresholds were significantly greater in patients with DM than in controls (RG: p < 0.001; YB: p < 0.001), and there were statistically significant differences in confocal cone density between the two groups at 1T (p = 0.016), but not at 0.5T (p = 0.094). In patients with DM, cone density at 1T was inversely correlated with RG and YB chromatic discrimination thresholds (RG: p = 0.014; YB: p = 0.007), whereas for 0.5T only YB was correlated with cone density (p = 0.009). Conclusion: This is the first study to investigate the relationship between cone density and chromatic discrimination in patients with DM and shows that there is a significant inverse relationship observed between confocal cone density and colour vision at the locations assessed within the foveal region, representing an advancement in oculomics.

Characterising the evolutionary relationship between colour visions and colouration in primates
Robert Macdonald University of Sheffield

Primates are remarkably colourful in comparison to other mammals. In particular, several species exhibit striking red-orange fur or bright red skin, thought to signal fertility or advertise social status in dominance interactions. One potential reason for this high diversity in red colouration is the primate visual system, which, uniquely among mammals, varies among species and even among members of the same species in the ability to distinguish shades of red and green (trichromatic colour vision). Trichromatic vision theoretically allows red colour signals to appear conspicuous to conspecifics yet camouflaged among vegetation to colour-blind mammalian predators, so it has often been assumed that the evolution of this visual system has facilitated the co-evolution of red.

Palmer Lecture: Animal Colour Vision
Daniel Osorio University of Sussex

In the Origin of Species Darwin saw that a ‘nearly similar taste for beautiful colours runs through a large part of the animal kingdom’, but cautioned that explanation was ‘very obscure’. For much of the 20th century research on animal colour vision was concerned with testing what was obvious to Darwin – that non-human species saw colour. I will look at how research in recent decades has built on knowledge of photoreceptor spectral sensitivities and models of colour discrimination to explore how non-human species, especially birds and fish, perceive and learn about colour. To finish I will offer a simple answer to Darwin’s question about why we might share a nearly similar taste for beautiful colours with species whose eyes are brains are very different from our own.

The neural mechanisms underlying colour afterimages
Christoph Witzel University of Southampton

Despite their fundamental importance, the mechanisms underlying negative colour afterimages are controversial. It is not clear whether colour afterimages are caused by adaptation in the cone photoreceptors, of colour-opponent neurons in the subcortical pathway, or require the assumption of yet unknown cortical mechanisms. The most common assumption in textbooks and contemporary research is that negative afterimages are cone- opponent. It has not been recognised that the role of those mechanisms can be distinguished because they make fundamentally different predictions about the hue and saturation of afterimages. To test these predictions, we developed experimental paradigms to measure the exact colours perceived in afterimages. The results reveal that afterimages do not align with cone-opponency but closely follow a well-founded model of cone adaptation (cone contrasts). The asymmetric way afterimage colours relate to inducer hue and saturation and mix with background colours is specific to cone adaptation. These findings establish that cone-adaptation is the sole origin of negative colour afterimages. The quantitative cone-contrast model provides a comprehensive, straight-forward explanation of the adaptive mechanisms underlying colour afterimages that resolves apparent contradictions and debunks wide-spread misconceptions.

The “super-importance of hue” in psychophysics, physiology and AI
Laysa Hedjar University of Giessen

Hue is thought to play a more important role for color discrimination than chroma. However, whether this is true appears to depend on the region of color space. In physiologically-based color opponent spaces, previous literature has shown that for orangish and bluish colors, hue thresholds are much smaller than chroma. But for purplish and greenish colors, hue and chroma thresholds are nearly equal. It is unclear why the visual system prioritizes some mechanisms over others. We first present neural evidence of this effect: we took magnetoencephalography measurements while subjects performed a simple discrimination task with either purplish or orangish uniform discs. We found greater amplitude modulation – indicating better discriminability – when the orangish stimuli differed in hue compared to chroma, and compared to both hue and chroma for purplish stimuli. Behaviorally, we explored whether the psychophysical differences would also arise in color discrimination of single-hue rendered objects, which elicit a distribution of points in color space. We found thresholds were merely elevated for the rendered objects compared to single patches of light. Hue superiority was present only for orangish colors, not purplish. We then analyzed multiple image databases to see whether the color distribution of objects found in the environment was biased and found that they overwhelmingly plot in the orangish regions of color space. We used the linear probe technique to interpret the internal representation of several deep neural networks trained on such biased image sets with high-level visual tasks such as object recognition and text-image pairing. The pattern of thresholds estimated from the networks, in particular the hue-chroma asymmetry, was similar to humans. We conclude that hue is indeed of superior importance for color discrimination, and that the peculiarities of this are shaped by the color statistics of our environment.

Chromatic Scene Statistics and Aesthetics
Anna Franklin University of Sussex

A popular idea from vision science is that visual perception and aesthetics are calibrated to the statistical regularities of natural scenes. For the case of aesthetics, stimuli that have the most ‘natural’ spectral slope, fractal dimension and chromatic distribution elicit more positive aesthetic judgements than stimuli which are uncharacteristic of natural scenes (e.g., Spehar et al., 2003). Here, we further investigate the relationship of chromatic scene statistics and aesthetic judgements of abstract stimuli and art.

First, we present a set of experiments which further investigate the finding that artistic merit is highest and visual discomfort is lowest for coloured ‘Mondrians’ which conform to the blue-yellow chromatic distribution of natural scenes (Juricevic et al., 2010). We test the hypothesis that aesthetic preference or visual discomfort calibrates to the chromatic scene statistics of an individual’s current ‘visual diet’. Using the same Mondrian stimuli as Juricevic et al., we compared the aesthetic judgements of people living in different environments (Ecuadorian rainforest, Quito City and Sussex), and different seasons (Norwegian adults tested at all 4 seasons). We captured the visual diet of people by using colour-calibrated head mounted cameras that they wore as they went about daily life, and we computed a set of chromatic statistics for the different environments and seasons. We find mixed evidence that aesthetic judgements calibrate to the chromatic statistics of people’s visual diet. Whilst there was a strong relationship between variation in aesthetic judgements and chromatic statistics for all groups, Quito participants in fact preferred the chromatic distribution that was most unnatural in their visual diet. In addition, although there was variation in Norwegian chromatic statistics with season and latitude, aesthetic judgements did not similarly vary.

Second, we present a set of studies which further investigate the role of chromatic statistics in aesthetic judgements of art. In one study, we find that a combination of chromatic and spatial image statistics accounted for over two thirds of the variance in adult judgments of the pleasantness of 40 van Gogh landscapes. Chromatic and luminance contrast as well as the proportion of greenish pixels were particularly important predictors. These chromatic statistics also predicted how long 4-6 month old infants looked at the landscapes, and infant looking and adult pleasantness judgements were highly related (McAdams et al., 2023, JOV). In another study we investigate the extent to which adult beauty ratings of a set of western oil paintings are predicted by chromatic and spatial scene statistics. We find that the perceived beauty of art increased the more similar the chromatic distributions and edge densities of the art were to that of natural scenes. However, for other scene statistics, images with greater deviation from natural scenes were judged as more beautiful. 

We discuss the implications of these findings for the theory that visual perception and aesthetics calibrate to chromatic scene statistics, and consider the potential mechanisms and timescales of such environmental calibration.

Funding from a European Research Council Consolidator Grant to AF (Project COLOURMIND, ref 772193).