In his seminal overview entitled Inner vision: An exploration of art and the brain, Semir Zeki postulated that 'artists are in some sense neurologists, studying the brain with techniques that are unique to them, but studying unknowingly the brain and its organisation nevertheless.' The present contribution aims to consider this view in relation to what appears to be an unexplored direction: the neuropsychological consequences of art depicted in black and white.
An historical approach is particularly revealing for outlining the issues. To consider a few examples, 500 years ago, the humanist Erasmus of Rotterdam wrote of the artist Albrecht Dürer,
'is there anything that he [Dürer] does not express in one color, that is, with black lines?… Is it not more wonderful to excel, independent of the radiance of color, at that art which [the greatest of the ancient Greek artists] Apelles distinguished himself under the protection of color?' 
Fast forward to the 19th century and Francisco Goya's The Disasters of War series of etchings (Figure 1); to the 20th century and Pablo Picasso's iconic picture Guernica, and Nick Ut's photograph of the girl burned by napalm during the Vietnam War bombing; and to the 21st century and the celebrated contemporary photographer and environmentalist Sebastião Salgado's 200 images of the vast landscapes of the Amazon rain forest in his work Amazȏnia (Figure 2). All these artists and photographers, while also superb practitioners in colour, selected black and white for their creations. Why, and what are the implications for understanding brain function?
Plate 3 from Goya's 'Disasters of War' series. Etching, c. 1810. Courtesy of The Metropolitan Museum of Art, Jacob H. Schiff Bequest, 1922. Image in the public domain.
'The heart is there yet'… Kampa do Rio Amonea Indigenous Territory in the rain. From Amazȏnia, c. 2021. © Sebastiao Salgado/nbpictures.
Although painting in monochrome was discussed two millennia ago by Pliny the Elder, perhaps the earliest hints that pictures which are coloured have different neuropsychological effects compared to images in black and white can again be traced back to the time of Dürer, when the Renaissance witnessed the so-called Disegno e Colore controversy: whether a painting's aesthetic value was attributable to its origin in the artist's mind that began with the initial drawings (the 'invention' or drawing—disegno), or the subsequent painterly execution of the picture itself that was frequently coloured—hence colore. Relevant here, the disegno with its points, lines and forms was most often executed in black and white and typically featured in preliminary sketches and under-drawings. Crucially, disegno was thought intellectual and theoretical in nature; in comparison, the finished work, colore, was considered more likely to be a lifelike and colourful imitation of nature. A different form of near monochrome painting, grisaille, often comprises shades of grey; Picasso's Guernica is a more recent example, but the technique dates over 800 years and some have suggested, without supporting evidence, that it can reflect the mental state of the artist.
Over the past century the different neuropsychological sequelae which appear to result from coloured or black and white pictures have been considered from the scientific perspective, initially by an unlikely investigator, Hermann Rorschach. His famous collection of ink-blots comprised both coloured and black and white cards, the former Rorschach held to be associated with more emotional and 'energizing' effects, and the latter more depressive or morbid thoughts. Rorschach's observations were taken up by Rudolf Arnheim, Harvard's first Professor of the Psychology of Art, who, while paraphrasing Rorschach's observations as 'color produces an essentially emotional experience, whereas shape corresponds to intellectual control', thought such a formulation seemed too narrow, particularly when it refers to art:
'It is probably true that receptivity and immediacy of experience are more typical for color responses, whereas active control characterizes the perception of shape … More generally, it is probably the expressive qualities (primarily of color, but also of shape) that spontaneously affect the passively receiving mind, whereas the tectonic structure of pattern (characteristic of shape, but also found in color) engages the actively organizing mind.' 
But as recounted elsewhere, Richard Gregory had perceptively mused in his Millennium Essay in Nature that Rorschach's inkblots 'might be able to tell us more about creativity than personality … and that reversing the test—from kinds of people to kinds of patterns—might show what stimulates creativity', and of course creativity forms the very basis of art.
Thus far the historical record suggests that different neuropsychological effects can result from images created in colour compared with black and white: the former more 'emotional' or 'energizing', the latter more 'intellectual' or 'cognitive'. Colour comprises one of several forms of surface feature, whereas black and white (and grey) images—which are necessarily features that remain in the absence of colour—are limited to the depiction of points, lines, edges and thus form, although it is acknowledged that abutting areas of colours too will give rise to a line or edge. Presumably these differences must be mediated by different cerebral processes through functional specialization, much of which takes place initially in the visual cortex.
Although functional specialization is now beyond doubt, the idea that the visual brain consists simply of cells responding to specific attributes such as colour, lines and form and are concentrated in particular cortical areas is now outdated. Zeki has summarized in considerable detail the evidence for 'The general principle … is (i) that there are multiple hierarchies in the visual brain—anatomical, temporal and perceptual—which are in different directions; and (ii) that these hierarchies operate in parallel but asynchronously'. He admits that 'Such disjunctive hierarchies appear to make of the visual brain a hopelessly intricate organ' and that 'the operations of the visual brain, and probably the brain at large, are massively asynchronous and parallel'.
A similar complexity arises in relation to circuitry that is harnessed beyond the visual cortex and which might be especially relevant to the distinct neuropsychological sequelae which follow coloured or black and white images such as those described above. For example, although, amongst several other structures, the amygdala in particular is generally considered central to processing emotion, and the lateral prefrontal cortex is considered central to cognitive processes, Pessoa has persuasively argued that such separation is 'problematic', arguing 'often true integration of emotion and cognition takes place, strongly blurring the distinction between the two' as a result of 'dynamic coalitions of networks of brain areas'. It has been further argued that structures including both the amygdala and pulvinar 'coordinate the function of cortical networks during evaluation of the biological significance of affective visual stimuli'.
Paradoxically, the very multiplicity of these complex processes inherent in the visual brain at both cortical and subcortical levels would appear to preclude the specialization necessary for the neuropsychological differences resulting from coloured and achromatic images. Yet functional specialization clearly remains and, despite the complexity of the visual brain referred to above, the neuropsychological effects experienced by patients who involuntarily acquire black and white or grey vision demonstrate that there must be some form of continuous 'thread' running from retina to visual brain to the psyche. These patients who sustain brain lesions resulting in acquired cerebral achromatopsia typically report that everything looks grey, but attention has been drawn to the remarkable paucity of descriptive accounts describing the actual neuropsychological effects of newly experienced deprivation of colour vision.
However, described in detail by Sacks and Wasserman, the most enlightening account is the case of the colour-blind painter, Jonathan I, who sustained traumatic damage to his visual association area. He first responded to the resultant greyness with distaste, depression and despair, but over time these psychological features were gradually replaced by acceptance, indeed contentment, and he was able to analyse the counter-intuitive rewards of 'becoming a night person'. This rare and admittedly largely anecdotal report reveals the neuropsychological effects of acquiring achromic vision; that these effects can change; and perhaps what was initially an emotional response subsequently evolved into one that became identifiable as more cognitive and 'intellectual'.
It should be noted that conclusions drawn from experimental studies are very different to those from clinical observations. Firstly, many imaging and neurophysiological studies have used black and white images as a baseline for comparison with results obtained with colour, rather than studies of black and white images themselves. Secondly, experimental studies frequently involve extremely short timescales, compared with the many minutes often entailed when carefully viewing a painting or a photograph.
While Sacks and Wasserman's patient may have eventually found his black and white world engaging, nearly always it is colour which is so attractive and so readily engages the viewer—a feature long known and exploited by advertisers. Why, then, would Dürer, Goya, Picasso, Rorschach, Ut, Santiago and numerous other artists have sometimes chosen to use black and white? I suggest that it is because these artists, sometimes perhaps subconsciously, chose to reject the very attractiveness of colour; rather, by using black and white they sought to promote a less emotional and what some would term intellectual response. Indeed, the distinguished art historian Ernst Gombrich controversially went so far as to comment that 'Great art, of course, must speak to the intellect and not to the senses'. Goya, Picasso and Ut were railing against war; Santiago against destruction of the environment. Colour would have rendered their pictures too 'pretty', and arguably artists such as these specifically harness those cerebral circuits which process black and white and convey form with which to engage cognition and the intellect. Of course, art in its broadest sense is a 'special case'; few would render architectural plans or engineering drawings in colour other than for purposes of identification and clarification, although it could be argued that the information they provide in black and white is indeed 'intellectual' and certainly not 'emotional'.
Considering those examples of the black and white artworks created over the past 500 years, it remains open to debate to what extent they indeed engage the intellect rather than the emotions. However, repeating the opening quotation from Zeki, that 'artists are in some sense neurologists, studying the brain with techniques that are unique to them, but studying unknowingly the brain and its organisation nevertheless', black and white artworks compared with those which are coloured may, unexpectedly, provide tools for the study of visual processes in the brain and for determining whether Rorschach and Arnheim were justified in distinguishing the emotional and intellectual neuropsychological responses to seeing.
Brain. 2022;145(4):1193-1195. © 2022 Oxford University Press