Book Review: Sight Unseen (part III). Are frogs conscious?

As I indicated in part II, although she has no conscious experience of the presence of a pencil, Dee Fletcher is able to catch a pencil using the same hand orientation as would a person with unimpaired vision.

As it turns out, some people have brain damages that cause the opposite effect: They can see and describe a pencil (they are consciously aware of the presence of a pencil) but they are unable to make the necessary movements to grasp it (Balint's syndrome). What these people have is not a motor problem. Balint "...could deduce that from asking the patient to point to different parts of his own body using his right hand with his eyes closed: there was no problem."

From the analysis of Dee Fletcher's case, it seems that when we are reaching for a pencil, we think that we need to be aware of the presence of the pencil, but actually not. We do not need to be aware of its presence. Dee Fletcher is not aware of its presence, but she can catch it. Reaching for objects is an ability that has been hard wired in our brain far back in our evolutionary history and it did not require consciousness. For this kind of motor acts at least, we are not better than "zombies".

A further indication that it is indeed so comes from experiments on animals:

When frogs catch preys, they use a different brain module from the one that guides them around visual obstacles blocking their path. This has been demonstrated in the following experiment:

First of all, they are two things that you need to know about frogs:

1) frogs’ brains can regenerate new connections when damaged.

2) the right eye of a frog is connected to the left hemisphere of its brain (and vice versa).

In these experiments, the optic nerves that brought information from the right eye to the "prey catching part" of the brain were cut. A few weeks later, however, the cut nerves re-grew and connected with the "prey catching part" of the brain but on the wrong side of the brain. As a result, when these frogs were brought in presence of a pray on their right side, they tried to catch it on their left side. However, when brought in presence of an obstacle on their right side, the frog correctly avoided the obstacle (this because the "obstacle avoiding part" of their brain had not been rewired.

The "prey catching part" in these frogs was now wired up the wrong way around.

But this did not mean that their entire visual world was reversed. It was as though the frogs saw the world correctly when skirting around an obstacle, but saw the world mirror-imaged when snapping at prey. Hence, frogs do not experience a global visual world created for all purposes. Frogs have specialized parts of their brain using visual information independently to perform different tasks.

Does that mean that frogs do not experience a visual world at all? Maybe they do, but as a matter of fact, they do not need one for catching prey or avoiding obstacles. By the way, we also do not need one for catching objects or avoiding obstacles. But we do experience a global visual world. This conscious visual experience might only be present in animals needing to communicate and/or to plan ahead...

For a long time I thought that any animal with a memory was conscious. Maybe frogs are conscious to some extend but it seems that they can function without experiencing a visual world as we do. Their kind of consciousness, if it exists, might be very different from ours.

Book Review: Sight Unseen (M.goodale, A. Milner) Part II:Doing without seeing

Now you will be surprised! You remember that Dee was unable to see the shape of things? Well, as it turns out, if you show her a pencil, she is unable to say what it is, let alone if it is held vertically or horizontally. However, ask her to grasp it and she will grasp it just like anybody else! With the same "on the fly" right orienting of her hand and with the same "on the fly" narrowing of her thumb - index distance! Just like if she could see it!


Just as surprising: She can walk around in a landscape full of obstacles without ever stumbling on any! She avoids them all like you and me!


The authors presented her a mailbox which opening was rotatable so as to enable orienting it in any chosen direction. When Dee was asked to hold an envelope and to rotate the envelope in such a way as to match with the opening of the mailbox: She failed lamentably. She seemed to orient her envelop randomly. But when asked to post the envelop through the slit: she succeeded easily, orienting correctly her hand just like you and me!


The authors asked her to grasp various objects while captors where posed at various parts of her hand so as to be able to analyze finely her moves. She grasps things in the exact same way as anybody else: adapting the orientation of her hand on the fly and adjusting the thumb-index distance to  the size of the object! Objects that she cannot "see" and which dimensions she is unable to guess!


As it turns out, Dee has the part of her vision controlling her actions intact but has the part of her vision constructing her perceptual representations damaged. She is living evidence that part of our vision driven actions are unconscious. We do not need to be aware of the orientation of a slit to be able to slide something in it. However, we do need to be aware of the orientation of said slit to be able to describe it!


We have many independent visually controlled processes in our brain. Many of them (grasping things, walking around avoid things, ...) still work even when, like Dee, we have lost the ability to consciously see these things!


In my next post, you will see how some people have the exact opposite problem than Dee.

Book Review: Sight Unseen (M.A. Goodale, A. D. Milner) Part I : A tragic accident

The undertitle of this book is "An exploration of concious and unconscious vision". This book relates some truly amazing facts about consciousness and vision.

The first chapter relates to a patient of the authors: Dee Fletcher. This woman had an accident. She got poisoned by carbon monoxide while taking a shower. As a result, she suffered some brain damage and lost part of her vision. Dee can still see colours but she cannot recognize her mother. She can see the texture of things but not their overal shape. She can see the hairs on a hand's skin but she cannot recognize a hand. She has vision...without shape. she can tell that something is made of red plastic or shiny metal but she has no idea of the shape of the object. Dee has difficulty to separate an object from its background;

The authors tested Dee scientifically, asking her to perform various controled tasks.

When presented with a line pattern, she could say that they were lines but could not say if they were horizontal or vertical.

When presented with a drawing of an apple, she could not recopy it; but when asked to draw an apple from memory, she did very well.

The rest of her mental live seems to be perfectly normal.

All this seems weird but the result of further tests is even much weirder! (To be continued)