Blindsight & the bakery facade

This Post provides a link to Chapter 9 of “What Scientists can Learn from Artists”, the book that presents the science that supports so many of the ideas and proposals found in my other three books. Its full title is “Blindsight, unilateral neglect and the bakery facade illusion”. It recounts what for me was a particularly exciting adventure into the mysteries of eye/brain function. This had its origins in research I was doing at the University of Stirling, Scotland, and reached its conclusion here in Montmiral, as a result of trying to understand why a student, who was good at drawing accurately, persisted in seeing the slope of a wall top differently from three other people sitting close to him. It turned out to be a question of his being taller than them and, as a result, he was relating the wall top to a slightly different background, with fascinating consequences: Ones which were to provide the substance not only of the chapter to which this Post is linked, but also of a closely related chapter in my book on drawing.*

Piazza del Duomo, Milan, which plays an important role in a fascinating, game changing story told in this chapter.

Two paradoxes

The bringing together information about “blindsight”, “unilateral neglect” and “The bakery facade illusion” provides yet another approach to making  clear that the process of “seeing” is complex. It also presents evidence that lead to two paradoxes, namely that:

  • we can all “see” what we cannot see
  • we can all “imagine” what we cannot imagine”.

Luckily knowledge of eye/brain systems can make sense of these seemingly senseless propositions. Also, it can alert artists to some deep seated problems they cannot avoid facing when drawing or painting from observation.



As I usually do when presenting book chapters, I am providing below an edited version of the “Introductory” to the chapter in question in the hope that it will whet your appetite for reading the chapter itself.


This chapter delves a little deeper into the subject of visual mechanisms and systems. It is one of the most important in the book because it provides information concerning the central problem as to how preconscious, bottom-up processes enable top-down control of the skilled use of eye/hand coordination. The first part takes the form of a detective story. The key to unlocking the mystery lies hidden in two experiments, relating to two visual impairment syndromes, each resulting from damage to a different part of the brain. Though other syndromes can be legitimately given the same names, they will be referred to as “blindsight” and “unilateral-neglect”. The second part of the chapter describes a powerful visual illusion, first noticed in relation to the facade of a building in Castelnau de Montmiral, S.W. France. This is shown to have general implications both for artists trying to depict scenes containing rectangular surfaces and for psychologists of perception, trying to understand the mechanisms underlying analytic-looking.


WHAT SCIENTISTS CAN LEARN FROM ARTISTS” CHAPTER 9 – “Blindsight, unilateral neglect and the bakery facade illusion”


*  “Axes of symmetry, recession and the constancies”: A chapter from my book on drawing that shows some of the ways the theory in this more scientific chapter can be related to practice.


Other chapters from “What Scientists can Learn from Artists”

Like the chapter to which this Post is linked, the links below can be used to access chapters from the middle section of my  book that elaborates on the science behind subjects that feature in the other volumes:

Go to top of page

Go to list of all other contents


9 thoughts on “Blindsight & the bakery facade”

    1. It is fascinating what science has been finding out about the nature of “seeing”. The plot thickens in the chapter that I will be posting next week. It tells about the astonishing (well it astonished me and all who were with me when we saw it for the first time) demonstration of Johannson that makes it quite clear how unimportant outlines (contours) are to recognition of moving objects. Perhaps we should not be surprised for “recognition” means seeing something as being the same on more than one occasion, and, as Degas and common sense have told us, outlines, even of the same solid, static object, perceived on two occasions, at marginally different distances or angles, are never quite the same (except in the unlikely event that both object and viewer stay in exactly the same relationship to one another). It wouldn’t be much use to us if we could only recognise things that we are seeing from exactly the same distance and viewing angle as on previous occasions. It follows that the processes that enable “recognition” cannot give much priority to outlines, which is why most people can navigate their lives perfectly well without paying much attention to them. No wonder I encounter so many students who find learning to draw accurately such a challenging struggle.

  1. Francis, this is intriguing and also quite difficult. I’m still not sure how Lovis Corinth did his self portrait. He can’t have used the same method as the man with his back to the Duomo in Milan, so how can he have produced it?

    1. Good question. One of my students, Keith Williams, worked with a unilateral neglect patient. He explained that this man had told him that he experiences a fleeting impression of a whole scene immediately before his visual world divides into two halves. However, the sense of an integrated whole is ephemeral, for it only lasted a matter of milliseconds. As soon as he focuses down on a target object, only half of it can be seen. The selection of the object to be looked at and the actions required for analysing it would have been predetermined by the preconscious use, first of recognition systems and then of action-organising ones. In other words, the choice of what to look at and how to interact with it had already been made.

      The first step in the visual part of any interaction with the target object will always involve focusing down, and it is doing so that necessitates the putting in place of an axis of approximate symmetry. In the case of unilateral neglect patients, this step is accompanied by the loss of half the scene they are looking at. Keith described how frustrating his charge found this outcome and how hard he struggled to reconstitute the fleeting sense of wholeness.

      My first thought was “why can’t the unilateral neglect patients just swivel their heads until the targeted object moves into the centre of the visible half of the scene?”. Later I was told that other researchers had had the same thought and that head swivelling was indeed the basis of the treatment of unilateral neglect.

      The good news is that this strategy can work. The bad news is that it can take a long time to do so. I cannot remember if I was informed about typical recovery times, but I am fairly sure that Lovis Corinth had to struggle on for many months or even years, before he could give the impression that he was painting normally again.

  2. I will always remember the excercise of the bakery roof … How sad it is not to see these lines anymore ! along the years, I saw many many good paintings, drawings of that view, Sarah’s works for exemple , astonishing !

    1. Just to explain to readers who do not know. The bakery building was converted and the characteristics which led to it being the source of the “bakery facade illusion” were removed.

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