Introduction to the drawing book

After posting thirty-seven of the chapters of my four books, I realise that I have missed out the “Introduction” to “Drawing on Both Sides of the Brain”. In the edited extract from it below, some general remarks are followed by a brief focus on two issues of fundamental relevance to what follows. Also, as an extra bonus, I have added three images .



A drawing by Auguste Rodin, one of two artists who set me on the way to scientific research



This volume differs in fundamental respects from earlier books on the same subjects. It offers new and practical guidance on drawing-from-observation. It does so whether the artist is seeking:

  • Greater accuracy.
  • More expressive power.
  • Ways of speeding up without losing control.

Its starting point is an analysis of widely used artistic practices and teaching methods. The next step is to explain not only why these have both proved to be of lasting value but also why, as they are currently taught, they have significant limitations.

A main source of evidence for the proposals elaborated in the following pages is research, done by myself and colleagues at the University of Stirling in Scotland, into how artists use their eyes when drawing or painting. This forced me to a number of conclusions that differ fundamentally from those provided by other authors, including those promoted by Betty Edwards in her extremely popular  book, “Drawing on the Right Side of the Brain”.

A similarity between Betty Edwards and myself is that both of us link our main explanations to contemporary science, with a special focus on neurophysiology. The difference is that the conclusions to which we come are radically different. While she relies heavily on a false theory of brain function, my arguments are are wider ranging, more up to date and demonstrably more relevant to drawing practice. As a result, I am able to offer a great deal of  new and reassuring information on human visual capacities, clarify the nature of the obstacles facing all who engage in drawing from observation and indicate effective ways of circumventing them.

During my 30 years teaching at the Painting School of Montmiral, I have had the opportunity of testing the research-based ideas on hundreds of students of all levels of attainment and a wide variety of aspirations. Although the outcome is clear and encouraging, a word of warning is appropriate. Both experience and theory make it clear that, while early progress will almost always be rapid, both for beginners and experienced artists, there is no escaping the fact that, as with all skills, the highest levels of attainment require a longer term commitment.

Experience and theory also show why early difficulties seem more daunting to some people than for others. Should this turn out to be your case, there is no need to be discouraged. No matter what your starting level, you can have confidence that, if you have the motivation to persevere, the new ways of looking and doing that I advocate will help you to far exceed your expectations.




A drawing by Edgar Degas, the other of the two artist who set me on the way to scientific research.


My experience as a teacher makes clear that everyone has difficulties with the accurate depiction of the outlines of objects. My research at the University of Stirling helps us understand why. It also sets us on the way to achieving the combination of accuracy, speed and expressive power mentioned above.le of

As the  science upon which much of my teaching depends will be unfamiliar to readers, a few words on two key ideas are appropriate. These centre on the subjects of “the variability of appearances” and “recognition”.


A useful preparation for understanding the nature of  the problem with which variability confronts us, is the realisation that no two objects or parts of objects ever present the eyes with the same outline, even ones that are classified as the same object-type. Indeed, because appearances are altered by every change in viewing angle and/or viewing distance, even the same object (unless it is a sphere) will never be identical in shape unless viewed from exactly the same position. Each set of relationships, whether between different sections of contour or regions colour will always be unique.

This fundamental truth of visual perception brings us to an extremely important implication of this unvarying rule of variability and the consequent uniqueness of all perceived objects. It is that, since, by definition, recognition depends on seeing something as being the same on different occasions, the precise characteristics of the contours artists seek to represent can only have a supplementary role in the processes that enable it.  Accordingly recognition must regularly involve overlooking the details of shape in favour of more general information. As we shall see in the following pages, the extent of overlooking can be huge.


Figure 1: A diagram of the working principles of the analytic looking cycle


Most people feel that they experience “recognition” as a conscious activity. But they are wrong to do so. As illustrated in Figure 1 (the details of which will be explained in due course), this key process in sensory perception always takes place before conscious awareness is achieved. The reason is that the function of recognition is not to produce an image of an object, but rather to access the knowledge required for activating instructions as to how to react to it.
As the diagram illustrates, the the knowledge accessed is always in the form of action instructions. These may be concerned with guiding arm, leg or other body movement or they may direct the movements of eye, head or body that enable us to target aspects of appearances that require special attention. It is only at this analytic-looking stage that consciousness has a role in visual perception.
But how does the eye/brain know where to target attention? It may help when seeking an answer to this question to remember that analytic-looking skills, like all other skills, are developed for specific purposes. Some skills, such as the ones learnt when very young, create platforms for more advanced ones. Anybody who sets themselves to learn a totally new skill has no option but to start with existing skills. All of these will be a compound of basic skills learnt as an infant, such as those required for grasping objects or for guiding the direction of crawling, and more advanced ones that have been developed later, such as those required for washing up, for using a computer or for any kind of sport.
This being the case, it follows that, if we wish to acquire complex visually mediated skills, we will have to learn the action instructions necessary for guiding appropriate ways of looking. Accordingly, although people learning to draw for the first time might have had experiences relating to other tasks that have allowed them to develop skills that could contribute the acquisition of drawing skills, they will never be enough. No matter how near the fit, they can only be of limited use unless appropriate ways of building upon them are developed.
If advanced artists assume that all this has no relevance to them, they should think again. The handicap of being saddled with old knowledge when facing new situations does not only apply to learning skills in hitherto untried domains of activity. It also applies to developing any skill at all beyond its present stage, no matter how well honed that may be. When Edgar Degas, one of the most skilled drawers in history, asserted, “I must impress on myself that I know nothing at all, for it is the only way to make progress”, he was making the claim that, no matter what the subject matter, fresh ways of looking will always be required.  In view of the unvarying variability of appearances, there is no alternative but to agree with him.
A more familiar and general way of expressing the above conclusions is that learning a new visually mediated task requires leaving aside bad, old habits in favour of adopting good, new ones. This book provides comprehensive information concerning how this can be done in the domain of drawing from observation
My son Thomas at a difficult moment in his life, a drawing that owed a great deal to my scientific research

An artist among scientists

Mutual benefits

During the twelve years I worked among scientists at the University of Stirling in Scotland, a transformation took place in my understanding of just about everything to do with the role of the eye and the brain in the organisation of the  the main perceptual and motor skills used in the making of drawings and paintings. PART 2 of my book “What Scientists can Learn from Artists” tells of experiments done by myself, colleagues and other scientists that made especially significant contributions to this exciting development.

Chapter 7, (accessed by clicking on link below) offers an autobiographical introduction the contents of PART 2 that gives a flavour of what I was up to in those years. A theme that runs through its pages is that the transformative learning was a two way process, offering benefits to all concerned. Time revealed many unexpected advantages in my being a combination of an experienced artist/teacher and a naive beginner in all the scientific disciplines in which I was to participate. My new colleagues found themselves faced with a drip feed of questions coming from unfamiliar perspectives that were to prove their value as catalysts capable of stimulating new ideas for a surprising number of highly expert scientists, working in a variety of disciplines. In return, their often participatory responses enabled me to put together the body of ideas that underpin the originality of my books, my teaching and, to an important extent, my work as an artist.




artist aong scientists
Two stripy paintings, made while the story above was unfolding.


Chapters from “What Scientists can Learn from Artists”

These deal in greater depth with subjects that feature in the other volumes


More information on my main colleagues


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Illusory pictorial space

Illusion in painting

Over the centuries, at least since the Italian Renaissance, artists have sought to represent three dimensional objects and scenes on two dimensional surfaces. By implication, this required them to create an eye-deceiving third dimension (‘trompe-l’œil).

To achieve their objective, they and their successors:  (a) mastered the laws of ‘linear perspective’, (b) delved deeply into the subject of ‘anatomy’, (c) explored the form-making properties of ‘gradation’, (d) recognised the importance of ‘overlap’,  (e) provided explanations for the phenomenon of ‘aerial perspective’, (f) explored whole-field lightness relations (‘chiaroscuro’) and (g) demonstrated the value of existing knowledge of the form of objects and the layout of scenes in influencing how viewers would perceive them (‘cognitive  cues‘).  In other words, over the centuries the artists have pioneered our understanding of just about everything that psychologists of perception needs to know about illusory pictorial space.

However, there was one big absence and it is this that dominates the discussion of illusory pictorial space in two of my books. In “Painting with Light and Colour” the subject is approached from the perspective of artistic practice. In “What Scientists can Learn from Artists”, which contains the chapter that can be obtained by clicking on the link below, its treatment has both scientists and artists in mind.

The chapter also touches briefly on the issue of what they saw as the immorality of deceiving the eye, which was to have both a decisive and long lasting effect on the evolution of painting from the Impressionists until the late 1960s at least. More on this in my other books.




A pictorial history of illusory pictorial space


 pictorial depth cues illustrated
Vittore Carpaccio (565-1625) – Lots of depth cues: overlap, shading, linear perspective, etc.


 pictorial depth cues illustrated
Claude Loraine (1600-1682) – Using aerial perspective to deceive the eye


 pictorial depth cues illustrated
Berth Morisot (1841-1895) – Brush marks made evident to emphasise the picture surface


 pictorial depth cues illustrated
Cézanne (1839 – 1906) – Doing his best to hold everything on the picture surface


 pictorial depth cues illustrated
Picasso (1882-1973) – Intent on keeping depicted surfaces near the actual picture space


 pictorial depth cues illustrated
Peit Mondrian (1872 1944) – Sought to depict a “spiritual space” within the flat picture surface.


Jackson Pollock – The critic Clement Greenberg, described him as creating as “A space within the picture surface”


Ellsworth Kelly (1953-2015) – Failing to eliminate illusory pictorial space


Michael Kidner (1917 – 2009) – Gave priority to keeping colours flat on the picture surface


illusory pictorial space illiminated
Ellsworth Kelly (1953-2015): Unambiguous flatness at last. But is it a painting or a sculpture?



Other Chapters from “What Scientists can Learn from Artists”

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Delacroix and his mistress

Delacroix and Elizabeth Cavé.

A portrait of Elizabeth Cavé by Jean-Auguste-Dominique Ingres


In an earlier Post I told of the teaching of Horace Lecoq Boisbaudran and its widespread influence. In it I did not mention another important figure who also developed a method for training the memory. Her name was Elizabeth Cavé. Like Lecoq Boisbaudran her method eventually found favour with the establishment and was to some extent introduced into the national curriculum. She was also, over some 30 years, a personal friend and confidant, often described as “mistress”, of Eugène Delacroix, who was something of a Father figure to the young Impressionists, including:

Homage to Eugene Delacroix by Henri Fintin Latour, including fellow students of Horace Lecoq Boisbaudran


Why I wrote a letter to LRB

With all this information in my head, you can imagine how my interest perked up when I came across a quotation from Delacroix in an article by T.J.Clark, published in the London Review of Books in October 2019. In this Delacroix tells us that he experienced a paradigm shift in his approach to painting, from being “hounded by a love of exactitude” to employing his memory to sift out “what is striking and poetic”. He also states that this transformation occurred as a spinoff from his “African voyage” in 1832.

On reading this endorsement of the virtues of channeling experience through memory, I was immediately reminded of the philosophy of Lecoq Boisbaudran. From there my mind jumped to Elizabeth Cavé and to wondering whether Delacroix’s change of direction had any link to her teaching method. When I discovered that their liaison had started in earnest in 1832, I could not resist the thought that either she had influenced Delacroix or, perhaps more likely, vice versa. If so, there seemed to be quite a lot to add to what T.J.Clark had to say. Below is what I wrote.

The letter

T.J.Clark (LRB 10-10-2019) quotes Eugene Delacroix as dating a change from being hounded by a love of exactitude to making work based on “recalling” what is striking and poetic. He asserted that it came after his “African voyage”, which mean after his return from Morocco in 1832. When I read this I immediately realised that this date roughly coincided with the beginning of his relationship with Elizabeth Cave in 1833. Whether or not her ideas were influenced by Delacroix or visa versa , she published ‘Le dessin sans maître’, which received a laudatory review from her by now long standing friend (in the ‘Revue de deux Mondes’ of September 1850). In it, she explained her method of teaching drawing which, according to her, she had been practicing since 1847. Key to this was training of the memory. Two years earlier, in 1848, Horace Lecoq Boisbaudran published a compilation of two texts, ‘L’Éducation de la mémoire pittoresque’ and ‘la formation de l’artiste’, in which he explained his method, also based on training the memory. His connection with Delacroix can be inferred from the personages in the 1864 painting ‘Homage à Delacroix’ by his pupil Henri Fantin-Latour, in which we see others two students of Lecoq Boisbaudran, Alphonse Legros and Felix Bracquemond. Also in the painting is James MacNeil Whistler who is know to have learnt Lecoq Boisbaudran’s method from Alphonse Legros and who famously demonstrated it to a doubter. He did this, first, by looking at an unfamiliar landscape and, then, turning his back on it and painting it from memory (for more about the influence of Lecoq Boisbaudran and its plausible ramifications see < >).

So how does all this relate to the quotation from Delacroix? The clue lies in his youthful “love of exactitude” being replaced by a more mature approach based on “recalling what was striking and poetic.” What Lecoq Boisbaudran would surely have argued is that the great man’s earlier obsession with ‘accuracy’ prepared him for his later personalised use of memory with all its benefits, for this was exactly what his teaching method (and presumably that of Elizabeth Cave) aimed at achieving. The main differences, he could argue, lay in the shortness of the time in which his students were expected to make their transition and the methodical progression from simple to complicated that characterised the learning exercises that made it possible. Surely, both Delacroix and Lecoq Boisbaudran would have concurred with Edgar Degas, significantly a great friend of Alphonse Legros, when he said, “It is always very well to copy what you see, but much better to draw what only the memory sees. Then you get a transformation, in which imagination works hand in hand with the memory and you reproduce only what has particularly struck you.”

Rodin acknowledged the importance to him of Horace Lecoq Boisbaudran’s memory training


As well as the personalisation of artistic output, the method had huge advantages in terms of rapidity of information pick up. The famous late watercolours (‘Cambodian dancers’, etc) of Rodin, another student and a lifelong admirer of Lecoq Boisbaudran and his teaching, illustrate both these advantages. Likewise the post-African paintings and drawings of Delacroix. Also, I find it hard to believe that there is not some connection here with Delacroix’s famous assertion that “any artists worth his salt should be able to draw a man that has been thrown out of a sixth floor window before he hits the ground.”

PS. For your interest, I was teaching on much the same principles as Lecoq Boisbaudran for at leat 25 years before I learnt of his existence. These I derived from research done at the University of Stirling in the early 1980s <>.


Why read my science book?

A paradigm shift

Back in November 2019 I started posting chapters from “What Scientists can Learn from Artists”, the book which presents the research and the science based ideas that that lie behind much of the contents of my three other books: “Drawing on Both Sides of the Brain”, “Painting with Light and Colour” and ” Fresh Perspectives on Creativity”. I set the ball rolling with with six of the chapters that describe research findings which were in large part responsible for:

  • Overturning almost all the preconceptions I had about the nature of visual perception.
  • Providing the building blocks required for replacing them with the coherent picture presented in these books.

When I first came across the material I have summarised in these chapters, their cumulative effect on me was more than just fascinating. It amounted to a paradigm shift. My hope is that reading them will perform the same service for others, particularly when buttressed by the contents of earlier and later chapters.

Below is an extract from the “Preface” to “What Scientists can Learn from Artists”, which summarises its structure. The chapters so far published in my Posts come from PART 2. In the next weeks I will be posting chapters from PART 1 and in the coming months chapters from PART 3.  I will wait to see the level of interest before I go on to PART 4, which I have reason to believe will be is considerably more demanding on non scientists.

Also below are links to already published Posts.

The structure of the book

Because the context of the knowledge of scientists and artists is so different, it seems prudent to provide a certain amount of background material which, while likely to be familiar to readers from one side of the arts/science divide, may well not be to those from the other. Thus PART 1 contains a number of general ideas both artistic and scientific many of which may well be familiar to one community and not the other, and PART 3 provides a basic introduction for non scientists to the nature of visual perception that emphasises the variety of visual systems involved in different aspects of visual processing. The function of PART 2 is to describe the main experiments used to underpin the theoretical speculations which lead to the general model of perceptual and cognitive processes that provides the subject matter for PART 4. Throughout the attempt has been made to present ideas in such a way that they will be understood by both groups.

Chapters from my book “What Scientists can Learn from Artists”

These deal with subjects that feature in the other volumes in greater depth.


A reminder

There are still places vacant for the 2020 sessions of the Painting School of Montmiral. Here a three photos to remind you of our idyllic setting and the seriousness of the teaching

book chapters
Castelnau de Montmiral from the South


book chapters
View from the breakfast balcony


book chapters
Out on the esplanade


Me discussing student work

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Constraint in artistic aids and practices

Is constraint necessary for creativity?

The purpose this Post is to provide a link to “Constraint in artistic aids and practices , Chapter 9 in my book “What Scientists can Learn from Artists”. As in several other Posts that publish book chapters, I include a slightly edited reprise of its“introductory”, in the hope it will whet your appetite and encourage you to click on the link below. I am hoping that when you have read all the chapters of all my books, you will realise that the answer to the question posed in the heading to this section is “Yes”. The images below illustrate two methods of constraint favoured by artists in former centuries that foreshadow ones that are widely used today: For example, photographs, slide projections, and computer controlled images. All of these, whether consciously or not, make use of constraints, the possibilities of which have been developed by evolution over the millennia, such as standing still, choosing a viewing distance or closing an eye al of which constrain input to our visual systems and, thereby, enable learning and creativity, its corollary.


figure 1 : Illustrates the lengths of which artists were prepared to go to achieve accuracy


Figure 2 : Illustrates a “camera obscura”, a simpler solution to the problem of obtaining accuracy than the one illustrated in Figure 1. However, both imply artist’s mistrust of unaided analytic looking



If we want to be creative, we will have to free ourselves from the constraints of old ways of doing things in order to go beyond them into new territory.

In this chapter, we take a step towards the goal of a practical understanding of how this might be done. It starts with my telling how I stumbled on the intuition that constraint may be a necessary condition for exploring the unknown, and provides examples of how the community of artists, whether consciously or not, have made much use of this possibility. Eventually I found myself coming to the seemingly paradoxical conclusion that constraint is necessary if we are to achieve either meaningful freedom or creative self expression. I also came to realise that the use of constraint is one of the guiding principles of our evolution as a species.

My approach to going deeper into the creative powers of constraint, starts with account of how I came to realise their central importance. I use the particularities of my own story because of the insights it furnishes relating to the creative process in general: long periods of gathering data, struggles with the confusion that they seem to engender, a sudden intuition that provides a lead on how order might be found and, finally, doing the work necessary to test its validity.

The inspiration for my breakthrough came when reading a book by J.J. Gibson, one of the most controversial yet influential perceptual psychologists of the day.




Other chapters from “What Scientists can Learn from Artists”

These deal in greater depth with subjects that feature in the other volumes


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The other constancies

My two previous  the Posts provided links to Chapter 12, “Local colour interactions” and Chapter 13, “Colour constancy”, from my book “What Scientists can Learn from Artists”. This Post provides a link to Chapter 15, “The other constancies”. Below the two images you will find an edited version of the “Introduction” to this chapter. As with other Posts, if you find that the subject matter interest you, you can click on the link below to the .PDF version of the chapter as a whole. The images illustrate two of the visual perceptual problems with which artists have had to come to terms.

Cézanne read Helmholtz and took the view that perceived reality is different from the measured reality that his predecessors sought to depict. When he tipped up landscapes and the tops of pots and vases it was because he believed that he was painting what he saw, even if he had to cheat to do so.


Introductory to Chapter 15

Colour constancy is by no means the only constancy of visual perception. There are many other constancies and all are fundamental to the ability of the eye-brain to make practical use of visually acquired information. Paradoxically, although their name suggests stability, they are responsible for the veritable “shifting sands of appearance” which, in its various guises, constitutes one of the main problems for artists seeking to obtain accuracy in drawings or paintings from observation. This is because they ensure that, when we look separately at any two similar features of appearances whether they be whole objects, parts of objects, sections of contour or colours, there is a very strong tendency to see them as being more similar to one another than objective measurement would dictate – often a great deal more so. Our visual systems upset the measured parameters of external relationship by relentlessly forcing them towards normative dimensions and values. As a result, the constancies involve enlarging and diminishing, squashing and stretching, revolving, darkening and lightening and modifying colour. Any list of the constancies of particular interest to the artist should certainly include (a) size constancy, (b) shape constancy, (c) orientation constancy (d) lightness constancy and (e) colour constancy.






Related chapters from “What Scientists can Learn from Artists”

Other Posts on colour and light in painting:

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Colour constancy demonstration

Colour constancy sets the ball rolling

It was unequivocal evidence of “induced colour” and “colour constancy” that triggered the realisation among scientists towards the end of the Eighteenth Century that colour is not a property of surfaces in the external world but phenomenon that is made in the head. Once this idea had been digested, it gained momentum and evidence began to pour in to suggest that all visual experience is a creation of the eye/brain combination. This game-changing paradigm shift was to lead, not only to the birth of the science of “visual perception”, but also to fundamental changes in the practice of artists,  either when drawing or painting from observation or when seeking control of pictorial dynamics. This is why the “constancies” and “simultaneous contrast dynamics” play such an important role in my books on the practice of painting and drawing. It is also an important part of the reason why I have written “What Scientists can Learn from Artists”, the last volume of my four volume series that explains the science behind so many of the ideas elaborated upon in the remaining three volumes. In going more deeply into the subjects that play such an important role in these books about artistic practices, it plunges us deep into the astonishing nature of the working principles of visual perception. Apart from the sheer wonder this must surely generate, knowing about the ways these determine how we “look” and how we “see” should have a significant benefits for artists: The deeper understanding and appreciation of the extraordinary things that are happening in our heads should help artists to:

  • Deal with the many practical problems that invariably face them when drawing or painting from observation
  • Make more creative use of their physical and conceptual tools.

The next Posts I will be chapters from the science volume.

A life changing event

This Post on “colour constancy” is the first from “What Scientists can Learn from Artists”. Its inspiration derives from Edwin Land’s irrefutable demonstration of the phenomenon of “colour constancy”, which proved to be a milestone in the search for an understanding of a subject that turned out to be of key importance to the understanding of how we “perceive surface”, “sense space” and are “aware of of lighting conditions”, all subjects of key importance to the ideas presented in “Painting with Light and Colour”.   

Below are:

  • A photo of the equipment used by Land for his epoch making colour constancy demonstration.
  • A reprise of the “Introduction” to the chapter and a link to a .PDF version of it (no need to read it twice: if you read it below, you can skip it in the chapter)
  • Links to Posts from “Painting with Light and Colour”, all of which (particularly chapters 7 to 11) have a debt to research that grew out of the colour constancy demonstration.


colour constancy demonstration
Figure 1 : The set up for Edwin Land’s first colour constancy demonstration, comprising a multicoloured “Mondrian”, three light sources, projecting the three light primaries, and a telescopic light meter that could take intensity readings from each patch of colour separately.



As explained earlier, a key event in my life was the encounter with Professor Marian Bohusz-Szyszko. The ideas he shared set me off on a lifelong journey of discovery. My first step was to set about testing his seemingly extravagant assertion that it is only necessary to follow two rules to guarantee a good painting:

    • There must be no repetition of colour on the same picture surface.
    • All the colours used must be mixtures containing at least a trace of complementary.

After four years of experimenting, I proved, at least to my own satisfaction, that there is a special quality in all paintings that abide by these two rules. It is difficult to describe, but it involves the creation of a sense of pictorial space and harmony.

Fortunately, a troubling paradox arose that would eventually have a profound effect on the development of the ideas presented in this book. It concerned the Professor’s physics-based proof of the invariable variability of colours in nature. This asserted that no two parts of any surface will reflect exactly the same wavelength combinations into our eyes due to:

    • The complexity produced by the inter-reflecting surfaces
    • Variations in viewing angles and distances
    • Atmospheric filtering

The paradox is that, if the light reflecting from two parts of a surface can never be characterised by the same wavlength combination, how could artists repeat colours on a picture surface? Even if two regions were painted with exactly the same pigment-colour, how could these appear as the same?

Other people might already have known how to resolve this mystery, but for many years I had no idea how to do so. My first inkling of a solution came after many years, as a result of reading a paper by Edwin Land, the inventor of the Polaroid camera. In it was a powerful demonstration of the phenomenon of “colour constancy” and an attempt to explaining it. What the demonstration showed was a region of colour within a multicoloured display (henceforth referred to as the MCD) being perceived as remaining the same, even when the experimenter changed the combination of wavelengths being reflected from it. I was excited because here were two colours being perceived as the same despite reflecting different wavelength combinations into they eyes? For me it was a eureka moment. However a big problem emerged for it was soon clear to me that the explanation of the colour constancy demonstration suggested by Land was not neurophysiologically plausible. An alternative had to be found. I could never have guessed at the treasure trove of discoveries that would come out of my struggles to provide it. This chapter describes Land’s demonstrations in the context of an earlier attempt at explaining colour constancy. The next chapter introduces our neurophysiologically plausible colour constancy algorithm.

The colour constancy chapter




Other chapters from “What Scientists can Learn from Artists”.


Chapters from “Painting with Light and Colour”

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Vision Group acknowledged

Members of the University of Stirling Vision Group

In many places in my books, I acknowledge the importance of the role of colleagues from University of Stirling in the development of the new science-based ideas put forward in them. In particular I mention cooperations with scientists from various departments who later were to join me in the University of Stirling Vision Group. The most important of these were:

  • Alistair Watson (Physics, psychology and computer imagery).
  • Leslie Smith * (computing).
  • Bill Phillips * (visual memory and brain function).
  • Karel Gisbers (neurophysiology).
  • Ranald McDonald (statistics and common sense).
  • Lindsay Wilson * (at the time working on aspects of visual perception).

Also, although Peter Brophy * did not join our group, he was an ever-available and important source of information on the biochemistry of the brain.

The founding of the Vision Group.

It was in  the Autumn of 1984 that Alistair, Leslie and I took the first steps in the setting up of the University of Stirling Vision Group, which was to have many meetings attended by the above named colleagues and other members of the various interested Departments. Its starting point was a package of ideas developed by Alistair and myself, and two core algorithms based on them, produced by Alistair.  These were:

  • A colour constancy algorithm, capable of modelling both spatial and temporal colour constancy, which was inspired by our interpretation of how this phenomenon is achieved by human eye/brain systems. As a preliminary step to achieving this main objective, the algorithm has to pick off the information about surface-reflection. Since it was obvious that the reflected-light contained information, we speculated upon how it might be used by the eye/brain. Due to my interest in picture perception, we focused on its potential for computing surface-form, in front/behind relations, and the wavelength composition of ambient illumination.**
  • A “classification/recognition algorithm”, based on our interpretation of how human eye/brain systems achieves their primary task of enabling recognition.***

We could not help being excited by the early tests of these algorithms and the speculations concerning their potential. In our  enthusiasm to push matters further, Alistair suggested we should seek the help of other researchers, particularly ones with expertise in:

  • Mathematics and computing.
  • Visual perception with special reference of visual memory.

It was at this juncture that, having decided on a name for what we were hoping would become a collaborative group, we contacted Leslie Smith for his mathematical and computing skills. But this was only a start. Once Leslie was on board, we approached Bill Phillips, whose long standing interest in visual memory had led him to take the plunge into the recently emerging domain of neural networks and learning algorithms. After many Vision Group meetings, much sharing of ideas, many hours spent working on implementations of algorithms, and the writing of a number of working papers, we decided to submit a suite of five grant applications to the Science and Engineering Research Council, who had let it be known that they were looking for groups of researchers working on the use of computers to model the functional principles of neural system. The stated aim of the SERC was to set up a small number of “Centres of Excellence” in this domain.  Not only were two of our grant applications accepted (one submitted by Bill Phillips and one submitted by Leslie Smith), but also our university was encouraged to create a brand new  Centre for Cognitive and Computational Neuroscience . This empire absorbed the University of Stirling Vision Group which ceased to have an independent existence. Its coming into existence also coincided with my departure from Stirling on my way to founding my Painting School of Montmiral, where I intended to put theory into practice both in my own work and in my teaching. I also had hopes of confirming and, with any luck, extending the theory. Also after leaving Stirling University, Alistair and I were founder members of a small software development company which used ideas developed within the Vision Group as a basis for creating an image manipulation tool. ****


* The links to Bill, Leslie, Lindsay and Peter relate to their current status. Alistair, Karel and Ranald all retired or died before the Internet became the essential information source it has since become.

** My book is full of examples of how fruitful this speculation proved to be.

*** In 1987 Alistair published:  “a new method of classification” in Pattern Recognition Letters, Volume 6, Issue 1, June 1987, Pages 15-19

****  Fluid Mask: a commercial outcome

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Preparation for the drawing lesson

The need for preparation

When new students at The Painting School of Montmiral are first faced with a live model in a figure drawing class, the majority of them give little time for preparation, even for long poses. Within a matter of seconds, even experienced artists have embarked upon active mark-making. It does not seem to occur to them that, before drawing the first line, it might be useful to spend time familiarizing themselves with the situation that faces them. If this is the case, they will almost certainly be denying themselves an important opportunity.

The feeling-based drawing lesson

At the heart of my book, “Drawing on Both Sides of the Brain“, is a  feeling-based drawing lesson that is described in three chapters. Chapter 9 (link below) is about getting ready for drawing the first line.  Chapter 10 (to follow) gives a blow by blow account of the main lesson in which:

  • Precise instructions are given concerning the preparation and execution of every line and every relationship.
  • Detailed reasons are offered for each and every one of these instructions. These relate to scientific studies of how artists coordinate their visual-analytic and line-output skills when drawing from observation.

Chapter 11 (to follow) suggests follow up exercises.

Preparation in previous chapters

All the chapters preceding Chapter 9  have been preparing for this lesson. Thus, they have discussed:

  • The pros and cons of widely used teaching methods.
  • The importance of scientific findings in the development of artists ideas.
  • How more recent scientific findings relating to the eye/brain’s analytic-looking and motor-control systems can help with issues of accuracy, line production speed, self-confidence and self expression.

Preparation in Chapter 9

Chapter 9 is likewise getting things ready for the drawing lesson, but in a much more specific sense, starting with practical issues such as setting up the easel/drawing board, establishing a viewpoint, deciding whether to shut an eye, etc. But it also introduces a certain amount of science-based information that will be useful in explaining reasons for the instructions used in the drawing lesson.




Diagrams and explanations from the Glossary

As Chapter 9 contains footnotes that refer to diagrams with explanations to be found in the Glossary, I have included three of these:

  • Figure 1 is the flow diagram representing the main factors that contribute to the analytic-looking cycle.
  • Figure 2 indicates regions of the neocortex (new brain) involved.
  • Figure 3 provides a mapping of eye movements showing glides and saccades.

Figure 1



The boxes and arrows in Figure 1 can be related to regions in the neocortex illustrated in Figure 2. Notice that Visual Area 1, which takes input from the retina via the optic nerve, supplies information not only for the preconscious processes that enable recognition, but also for the subsequent consciousness-related ones that accompany analytic-looking (This is why it is labelled “twice used information resource”).

In addition, the diagram indicates the key role of memory stores (whether short-term or long-term) in enabling both recognition and learnt-actions. It also calls attention to the importance of context and feeling in building them up and  of whole-life experience in determining how they do so. But perhaps the most important lesson that can be drawn from it is that recognition takes place before analysis. Thus it can be asserted that, in an important sense, “we know what we are looking at before we are consciously aware of it”.

Recognition also takes place before the implementation of learnt-actions, such as those that guide artists when drawing contours or making any other kind of mark. Accordingly, we can draw “what we know” about an object-type on the basis of the multi-modal, preconsciously acquired information made available by the very limited number of looks that are required to enable recognition (seldom more than one or two). In other words, the eye/brain acts as if further analysis of the object itself is unnecessary. The diagram also indicates the role of non visual-inputs in enabling recognition. For example, we may recognise something, in whole or in part, by its sound, smell or feel and can in princple complete the process of doing so without confirming what it is visually.

Figure 2


Figure 2 maps a number of the functional divisions in the neocortex (new brain). These can be related to the stages of the analytic-looking cycle as diagrammed in Figure 1. Thus:

  • The arrow labelled “visual cortex” points to the location of “visual area 1” in Figure 1
  • The region from there down to temporal lobe corresponds to the labels “preconscious multimodal processing” and “recognition” in Figure 1.
  • The motor cortex mediates “learnt actions” in Figure 1.
  • The parietal lobe underpins “conscious analytic-looking” and “the constancies of shape, size, and orientation” in Figure 1.

However, the area in Figure 1 labelled “context” and “feeling-based memory reflecting whole life experience” is more difficult to place, but would include:

  • The “somosensory cortex” (an essential part of the “feel system”).
  • Parts of the frontal lobe” with its links to the emotional centres in the old brain. These are thought to be involved in the choice between “good” and “bad” actions and the determination of “similarities” and “differences” between things or events, both of which are essential to developing the skills that underpin drawing from observation (as explained in Chapters 9 – 11).
  • The frontal lobe, along with old brain regions including the hippocampus, is also thought to play an important part in the creation and retention of  long-term memory.

Figure 3


Figure 3 is based on a photographic record of typical eye movements in which slow moving glides (wobbly blue lines) are interspersed with faster moving saccades (straight red lines with arrows to represent speed). The glides provide a constant stream of same/different information, while the saccades enable an intermittent averaging of input that is useful for neural computations that require knowledge of ambient illumination. The average glide/saccades combination lasts approximately one third of a second.


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