My question to you as reader of this homepage is straightforward:

Does our surrounding world exist as we see it?

If your answer is YES, you really have to read this article. If your answer is NO you also have to read this article. Intellectually you may be are able to realize that the image of the world around you is a construction made in the brain. But can you really accept this emotionally that the world out there does not exist as you see it? I can't yet. I am so used all my life to think otherwise that it is impossible to change this illusion mentally.

Looking out of the window, I can see a beautiful birch with yellowish green leaves and in the foreground a border with red roses. From what I have just said there is no birch nor roses out there, they are constructions made inside my brain. I can only receive a small part of the electromagnetic wave spectrum of the visible light that is reaching the birch from the universe. I can not see the heat the birch is emanating to its surroundings. I can not perceive millions of other things from this birch. Yes, I can take an infrared camera to catch the heat waves or another apparatus to hear sounds coming from the tree.

Another example is when someone is looking at me, let say a customs officer, he will compare the image he got from me with the photo on my passport. He is receiving in his eye the reflection of the visible light. When I would show him my Kirlian photo he would have a complete different view of the extension of my body. The electrostatic radiance of my body seen on the Kirlian photo makes me considerably bigger. But also this image is not in correspondence with the actual extension of my body. As you my length would be instead of 1.76 m (as indicated in my passport) 2.10 m!

Figure 1. Drawing after a Kirlian photo taken from the author shows the aura in different colors. (The original aura photo was too vague for reproduction)

How far it really reaches in space, I don't know. It all boils down to the way you look at things. A roentgen or infrared photo of my body would also be quite different.

It is very important to realize that everybody has his own image of the world. The only real thing he knows is that this image is only his own reality and nothing else. He and I will never know what the real world is alike. That reality out there will always be unreachable for us. The moment we make an image of this reality it collapses due to the distortion of this image in our brain. It will also be a tiny fraction, we can perceive with the receptors at the back of our eyes of the electromagnetic waves of the visible light.

It would be an enormous difference, if we emotionally accept this hard fact. People would be more tolerant. They would be not ready to accept the "truth" or belief of someone else or the dogmas from religions or systems. All this forms the reason, why I think it is important for us to know more about the functioning of our body and especially of our senses.

In former times we used to place ourselves in the center of the universe. After Galilee, Copernicus, Newton, Planck, Einstein, Heisenberg, Bohr and many others we know now that we are living on a tiny planet in a huge universe. However we still emotionally think, that we are in the center of the universe.

As we all know the Earth is turning in one day around itself and in 1 year around the sun. The sun itself is also rotating. It turns once every 27 days. Our solar system is turning around the center of our galaxy in 250 million years. Strange thought if there was no matter in the universe except the Earth, the question could be asked: Is the Earth turning? In relation to what? It is not so surprisingly that in earlier time we thought that the Earth was the center of the universe. Stars, sun and planets seem to be turning around the Earth. Some people even in recent times believed that the Earth was flat.

We know all this but I will show you that emotionally, we are still thinking that our Earth is flat, that the sun rises in the morning and sets in the evening. In two examples I can demonstrate that your emotional thinking is still dating from the middle ages!

two answers

What of our thinking about the free will? Many people still believe that they have a free will and a free choice. We think that we have the freedom of the commons.

We think, that we can tear up the Earth to get the oil, gas, iron and so many other valuable things. Look at the so-called primitive people, they did not dare to touch the Earth. It was holy ground for them. Look at our behavior. We only are digging deep holes in the ground, which we also cover with concrete.

Link 2: urbanization of Washington D.C.

We really lost the contact with our home base: the Earth. It boils down to the fact, that we are too greedy in the way of our thinking. We want more and more, we are not satisfied with what we have. We are going out with our bulldozers to destroy the rainforest to catch some of the big trees to use for our homes. We forget that these rainforests are our own lungs. Do we have still time to avoid disaster? No, with the way we are educating our children, the way we are behaving and especially the way we are thinking about nature and ourselves. My last hope (maybe wishful thinking) is that we have to know more about our last potential: our brain (the 3-pound universe) in relation to our body and the world around us. For this reason I am going to make an expedition to this last resort.

What part of our body is in direct contact with the environment? The skin is our biggest sense organ! A human being seen from the outside is a leather bag filled with chemicals. The surface of this bag consists of dead material. The upper part of the skin, the hairs, the nails consist of deceased cells (did you know that the greatest part of dust in your house consist of flake of dead skin cells). Inside this bag is a living human being consisting of millions cells of 350 different cell types. All built from fertilized egg. The wonder is that these cells are self-producing and can absorb all sort of chemicals and are capable of producing energy, which gives us a great number of possibilities. We can walk, we can swim, and fly (with artificial aids). The most complex structure is the human brain. The human brain possesses an estimated 100 billion nerve cells (neurons) and 500 million supporting cells (glia's). Neurons are separated by a very narrow gap of thousands of a micron. The gap is called synapse. We have in total 60 trillion synapses. Let us assume that we can count a synapse per second. How many years do we have to count? Nearly 2 million years (1 year has 365 days, 8760 hours, 535,600 minutes and 31,536,000 seconds).

In a publication (M.E. McCourt, 1997) I read another arithmetic sum:

The brain is the most complex structure we have seen until now in our universe, but also the most underdeveloped part of our body. Here lies a greatest challenge for our future. We have to change our way of thinking. But what is actually thinking?

In Webster International Dictionary:"The action of using one's mind to produce thoughts".

Immediately we are confronted with the meaning of the word mind.We as human beings are obliged as a necessary evil to "think" in opposites.It was already Heraclitus (6th -5th cent. B.C.), who claimed that every thing needs an opposite.

But he also said that they both form a unity. Like mind and matter are different aspects of one human being, inseparably united. We, as thinkers, need to divide the world around in us in opposites. We have to realize that all these opposites are constructions of our mind. We have, otherwise it is impossible, to think or to communicate with each other. Everything we think or say are just fragments cut out the total world. Reality is an illusion. We will never be able to grasp nature in all its aspects. The only thing we can try to find out is how many relations there are in nature. Maybe only to come to the conclusion, that we only can confirm statements of philosophers like Socrates:

or like Descartes:

The most important thing is that we must try to look at "things" constantly from different angles.

Every scientist must admit he has a belief: "he is looking for relations while in the back of his mind some kind of order must exist even if he claims that it is a chaotic order or an ordered chaos". The only thing he tries to find out how human beings are related to this order. It must in one way of another make sense.

Many theories seem completely contradictory, but if we look more carefully we can only see that they are looking at nature with different "spectacles".

A good example of this dichotomy is the gap between quantum- and classical mechanics. The first is "looking" at cold, small and light things and the second at large, heavy and hot things. Dyson recently made a very interesting thought during a lecture (Cohen and Stewart, 1994). Another way of looking at this gap is to consider all past events from a classical view and the future events with a quantum view.

In the classical (Newtonian physics) view time is irreversible: the arrow of time according to the second law of thermodynamics. In the quantum mechanical view time processes can be reversible. Another good example of a dichotomy is the duality of light. We can observe it either as particles or as waves, never both at the same time. Reality collapses when we observe it or with the words of John Wheeler "to be is to be perceived".

We start always with our way of looking with an egocentric look. We can look at the macro- or the micro world.

I found a remarkable comparison between the two physics

Can picture it--- Cannot picture it

Based on ordinary sense perceptions--- based on behavior of subatomic particles and

systems not directly observable

Describes things; individual object in space andtime---Describes statistical behavior of systems

their changes in time

Predicts events---Predicts probabilities

Assumes an objective reality "out there"--- Does not assume an objective reality apart from

our experience

We can observe something without changing it ---We cannot observe something without changing it

Claims to be based on "absolute truth"--- Claims only to correlate experience correctly

The most astonishing is that when we are looking at the sky we observe only past events (classical mechanics) sometimes of billions years ago. But when we are looking at the micro world we enter the world of so-called elementary particles (quantum mechanics). In this micro world we lose every sense of the quality of the observed thing. The elementary particles are looking alike if it is from a crystal, plant or animal. It is by the assembly of all these particles that we can observe a certain form or quality. We can observe light as particles and as waves. Just how we look at it. The famous experiment of Young in which a photon goes through one split and is interfering with itself when another adjacent split is opened. This interference pattern can be seen on a screen. It is like the sound of clapping with one hand! If only one split is open the photo is projected on a screen and behaves as a particle. Both are no the real world. The energy of light is a superposition and when we want to see it than this superimposed state collapses as a particle or a wave. Just how we like to look at it.

Figure 2. The sound of clapping with one hand.

Upper right figure: Pattern of intensity at the screen, when just one slit if open. Manifestation of light as particles (photons). Lower right figure: Pattern of intensity when both slits are open. Manifestation of wavelike behavior, interference patterns with distinct bands on the screen. (After Penrose, 1989)

All these examples show clearly, that we can perceive our world from all sorts of angles. All images seem different, whereas we postulate that we are looking at the same world. Our task is to show how conditioned we are and we unconsciously come up with actually the same image. But this image is not the real world but a construction of our mind. Every question like: "can a plant or animal think" is always answered by a human being, and therefore strongly biased. They use other instruments to conceive the world. A bee is capable to register ultraviolet waves and snake infrared waves. We will also show our falsehood of our egocentric look to place Homo sapiens on top of the bill. The more we study ourselves in comparison with our surrounding world the more we realize, that we are just a special form of life, with no further qualifications than that we are the last result of the experimental factory of nature on this planet. On Earth we have special conditions that life is bound mainly to elements as carbon, hydrogen, oxygen and nitrogen. Maybe that elsewhere in the universe life is bound to elements like silica?

The central core of our capacity of thinking is our nervous system.

How works this last resource? Let us start with our most precious sensory system: vision. With our eyes we perceive the world around us, it is influencing for a great deal our behavior.

Perception depends on a simultaneous cooperative activity of millions of neurons throughout the entire brain. Chaos underlies the ability of the brain to respond flexible to the outside world.

I will now focus on how we perceive the world with our senses. For us human beings vision is the most dominant sensory input to perceive the world around us. By asking people how far they can see, nobody answer this question correctly. Everyone is thinking that we are looking to the world and nobody is saying we are not looking in an active way but perceiving the world around us. With more then 200 million receptors at the back of our eyes we receive electromagnetic waves. Our visible light is only a very small part of the electromagnetic spectrum that reaches our body everyday. "Fortunately for the survival of life on Earth our atmosphere is protecting us from roentgen rays" (K.A.Pounds, Science Journal, April 1970). This is the other way round, a nice example of the Procrustus thinking *). Or what to think of the next sentence in the textbook of Geochemistry of Stryer (1988): "11-cis retinal gives rhodopsin a broad absorption band in the visible region of the spectrum with a peak at 500nm, which nicely matches the solar output"

*) Procrustus thinking: in one of the Greek myth there was a man named Procrustus who lived beside the road, and had two beds in his house, one small and one large. Offering a night's lodging to travellers, he would lay the short men on the large bed, and rack them out to fit it; but the tall men on the small bed , sawing off as much of their legs as projected beyond it. (Graves, 1955)

.

Figure 3. The electromagnetic spectrum. It can be measured in wavelength (distance between successive waves) and in frequency (the number of waves per second). The enlarged area shows the visible spectrum in nanometres. The curve of the figure indicates how much energy our atmosphere absorbs, especially the protection for dangerous ultraviolet rays for humans.

We have used the radiant energy from the sun to produce certain chemicals that allow us to "see". We use rhodopsin to covert light in the photosynthetic process. The narrow band between 350 and 750 nanometers. This narrow band of response is clear evidence of selection in evolution and is related to the sun which has a peak of energy at 500 nanometers (1 nm= nanometer, 0.000,000,001 m).

This passive input does not reflect the words on vision in our language. Some examples show us clearly that we are ‘seeing’ vision as an active act. "Give an eye, throw eyes at, and see to it". In the Oxford dictionary we read the explanation of the word eyeshot: "The distance that the eye can see". The eye is not seeing in an active way, but only perceives the world.

Professor Kalat asks a student during a final oral exam for the Ph.D. degree in psychology:

"How far can an ant see".

The student answered:

" Presumably an ant can see 93 million miles - the distance to the sun".

He was falling into a trap. He thought that he was seeing objects being "out there". In fact he receives the world around him through the electromagnetic waves hitting his receptors at the back of his eyes. (How would you have answered the professor?) (Kalat, 1992).

In other senses, like hearing words expressing, always is an passive act like the meaning of the word listening: to pay attention to sound, to hear with thoughtful attention, to be alert, to catch an expected sound.

Not only don't we realize that we are actually not looking at the world, but perceiving the world around us, we also are distorting the image we are receiving. We have even to learn to perceive. Children born blind and operated at a later stage have difficulty in learning to see. An eight-year-old blind patient has been trained before operation to become acquainted with objects by touch. After the operation he was very much deceived. He showed no visual recognition of any objects presented though they were perfectly familiar to him by touch. It took many months training the boy to recognize objects by sight and two years after the operation much of what was learnt visually was forgotten. Zeki, 1993:

Another example of the learning process of perceiving is the reaction of a man of 50 years who could use his eyes, after an operation, for the first time in his life. He was struck by how objects change their shape, when he walked around them. This seems so naturally to us, that we do not realize this remarkable capacity of the brain. We can recognize objects even when the retinal image of an object changes in viewpoint, lighting, size or location. Our perceptual apparatus has learnt all this during our life (Wallis and Bulthoff, 1999).

A remarkable example of deprivation of sight during the early years of life is of a boy found in Nuremberg in 1828. He was about 16 years old. His name was Kaspar Hauser.

Before coming to Nuremberg he had only ever seen one other human. He had lived in a dimly lighted container about two meters long, one meter wide and one and a half high. There was a straw bed for sleeping. He found water and bread next to his bed every morning.

Anselm von Feuerbach described him in 1832:

He heard from his container the church bells ringing. They asked him:

His answer was very surprising:

"The container, because if you turn your back to the tower it is not anymore there, whereas the container is all around me".

Figure 4. Kaspar Hauser

I think this is a good metaphor for our vision of the world around us. What is bigger: a star in the sky or the Earth you are living on? If you turn your head away from the star it is not anymore there, whereas the Earth is all around me. We perceive our sleeping chamber bigger than the cosmos.

Our body constantly is exposed constantly to all sorts of vibrations.

Well let us have a "look" what happens after the electromagnetic vibrations have reached the receptors at the back of our eyes. The eyes are the protrusions of the brain. Light does not exist without us. Strange to realize that all we perceive from the world around us, is a construction made in our brain. We are thinking that the world is out there. The same applies to hearing a sound: we really think it comes from the source of the sound. In fact we are creating the image of the world inside us. I personally think this is mind boggling. The same is when hearing a sound that you really think from it come from the sound source. In fact air vibrations reach our ears and the sound is produced inside our head. When a tree falls in a wood and nobody is there, there is no sound only air vibrations. Also very weird is the fact that all vibrations are reaching at different moments my body, but by a special mechanism in the brain these signals are synchronized. It seems that they are arriving all at the same moment. Our brain converting air vibrations (330m per second) in sounds quicker than light vibrations (3 million meters per sec) within a range up to 10 meters around us. Beyond a distance of 10 meters it is vice versa. (Lighting first, thunders later). It serves a survival mechanisms. We hear first at short distance before we see the danger.

When we are receiving the electromagnetic vibrations of the world around us we are converting these signals into another image than a normal photo camera will do. I give an example. Hold let say a glass in your hand and move it towards you and away from you. A photo of the glass will show a bigger glass when it is closer to the camera than when it is a bit farther away. You can prove it yourself that apparently the glass has the same size and shape when moving it towards or from you. This is called the constancy in size and shape. This is very strange indeed. The electromagnetic waves coming from an object are always changing. Thanks to the mechanisms of the size, shape and brightness constancy we are not confused by the fact that the object has changed by moving towards or from us, or that the light falling on the object is constantly changing. It is also very strange that we can reconstruct a three-dimensional image of the world from a two-dimensional projection on our retina. The visual system takes several variables into account in order to maintain the stability of the world around us. Among the constancy's that are of particular relevance to the present discussion are those of size, shape, color and velocity. The human perceptual system can maintain a stable perception of moving objects despite the fact that the position of the retina stimulated by object changes as the eyes move. This is called visual direction constancy.

Size and shape cooperation between two regions that are a priori known to extract two different types of information. On that has limited invariant capacities for object recognition and the other that can extract object locations in the periphery and drive eye movements to reset the pattern in the central region.

What we perceive is often not what exists in reality. The 3-dimensional world, in which we live, has to be constructed in our brain from its 2-dimensional projection on the retina.

The brain is doing this by using clues and assumptions, mainly based on past experiences. When we have many possibilities to choose from, we normally take the simplest or the most common experience.

Figure 5. Children of four years shown a rod occluded by a box (a). When shown a rod without the box before it they conceptualize it as a whole unit (b). The two fragments surprised them because they perceived the rod with the box before it as a whole unit (c) (After Spelke, 1985 and Gazzaniga, 1992).

Spelke (1985) gives a good example of visual learning experience. Four-month-old infants were presented with an image of a rod partially occluded by a box. The infants were then presented with an image of the rod as a whole object or as two fragments with a gap where the box occluded the object. The two fragments surprised them because they perceived the rod as a whole unit even though they could not see the whole rod. Spelke concluded that the principles of cohesion, boundedness, substance and spatial temporal continuity are central to thought for our species in childhood as well in adulthood. The core of knowledge that is presumably inherited is built upon throughout life and results in what become to every adult's the ability to perfectly predict a variety of physical events such as the manner in which paths connect through unoccupied space. Spelke predicts that a child who does not become equipped with a core of initial theory will not develop a systematic theory about the knowledge in question. (Gazzinga, 1992, p. 117)

These findings are evidence that the brain has an operating mechanism for apprehending objects on a representational level.

Assad and Maunsell (1995) did experiments on monkeys. They recorded the posterior parietal cortex while the animal viewed a visual stimulus that disappeared. During this absence they found that about half of the neurons were found to be significantly more active on those trials in which the stimulus could presumed of be moving rather than stationary. They conclude:

"The activity was present in absence of either sensory or motor output suggesting it may indeed constitute a generalized representation of target motion ".

As we have seen the capacity of perceiving the world around us is not only genetically determined but also by a process of growth of nerve cells after the conception of the fertilized egg has taken place. The process of maturation of the most important sensory system gives an excellent view of the different visual areas and their workings in relation to each other. It is very important to realize what happens in the earliest stages of our existence. Also what can go wrong when in early infancy the environment under which the young born is developing is not optimal. Visual experience and genetic factors are playing a role in the development of visual attention on the world around us.

In the first months of our life the main four visual pathways are maturing in different ages.

First is developed the peripheral vision, the central part is still very immature. This peripheral vision is very important because dangers lurk in the corners of your eyes! The most important visual processing area in the brain is the subcortical structure called the superior colliculus. Already after 24 weeks of pregnancy the adult pattern of lamination can be observed. The retinocollicular visual pathway begins to myelinate (speeding up the transmission of signals) about 2 months prenatally and the process is complete three months after birth. As we will see later the retinocollicular has more nerves (they are crossed, i.e. from left eye to right brain) from the peripheral (temporal) visual field than the nasal visual field (Tranel, 1995). The retinocortical pathway begins at birth and is completed 4 months after birth. The movement of the eyes is jerky (saccadic). The smooth pursuit is not yet developed (this eye movement needs more complex computations). The movements of the eyes are always followed behind the movement of the stimulus. No calculation of the future location of a moving object is computed.

When the child is about 1-month-old new pathways and nerve cells are developed. Of great importance is the possibility to inhibit the working of the superior colliculus. The cortical visual area is exciting the basal ganglia and on its turn is inhibiting the superior colliculus. The function of this pathway is to inhibit orienting toward peripheral stimuli. Its development may account for the obligatory attention of infants around 1 month. The child is now able to focus on a special target. Sometimes this fixation period can last 30 minutes. It is difficult to disengage their gaze from a stimulus easily.

Around two years of age there are two changes in visually guided behavior. It is able to pursuit a moving target. The tracking is still lagging behind the movement of the stimulus. This smooth movement reduces the size of the target, however these two mechanisms are not largely independent of each other. We see that nerves coming from the fourth layer of the cortex are connecting an area MT (V5) that is designed for the processing of movement. The central vision is not only processed in this period but also influences motor output.

In the period between 3- 6 months old, the fourth pathway is developed. The maturation of layer 2 and 3 of the visual cortex allows the connection of the parvocellular (P) pathway (color) via V2 and V3 and the frontal eye field (FEF). This pathway is also connected with the temporal lobe (IT). An area designed for the recognition of identification of objects. The child is now also capable to anticipate the moving stimulus. Binocular functioning is developed due to the segregation of the ocular dominance column in the cortical layer 4c. (Johnson,1992).

The reason that I discussed this early development of our eyes is to show how important the first months after the conception for the development of our brain actually are. When we will have a better use of our last resource, the brain, we have to realize this and every expectant mother has to know this.

7. Cultural and environmental effect on perception.

Not only the physical development of our brain is important to know but also the role of the culture in which we live is of importance for the development of our brain. I did not find many studies concerning this subject I have found in the literature.

Most illusions appear to hold for all human beings. There are however some exceptions. Some optical illusions seem to be culturally variable. The Müller-Lyer illusion is one of them (F.C.Müller-Lyer, 1857-1916 inventor of the most famous of all illusions). For us westerners we immediately think that the vertical lines are actually the same size but that the right-hand line appears to be substantially longer. Müller-Lyer offered an explanation of the illusion: "the judgment not only takes the lines themselves but also, unintentionally, some parts of the space on either side". Segall, Campbell and Herskovitz (1966) reported that this illusion may be absent or reduced among the Zulu people in South Africa. They live in circular huts with arched doorways and have little experience of our rectangular buildings. We interpret oblique and acute angles as displaced right angles and perceive two-dimensional drawings in terms of depth.

Figure 6. The Muller-Lyer illusion

Coren et.al. (1994) showed that we are more biased by vertical and horizontal line than oblique lines. The vertical gives us the impression that the vertical line is longer. This illusion is stronger for people who are familiar with straight lines receding over a considerable distance.

The shape of the visual field on the retina is not circular but has an asymmetric composition. With binocular viewing the visual field is ovoid, its horizontal axis being nearly half again greater than its vertical axis, about 200 degrees versus 130 degrees. This is the main reason for the so-called horizontal -vertical illusion. A vertical line occupies a greater proportion of the vertical field than physically the horizontal line occupies the horizontal field. Armstrong and Marks (1997) reported of experiments on this illusion and found that people judge a vertical line 14% longer than a given horizontal line of the same length.

It is also good to realize that the nasal lower part is smaller due to the nose bridge than the upper of the visual field on the retina.

Overestimation of height is greater for real objects than for objects in pictures. It is the physical size that is of importance rather than the objects represented size. The horizontal vertical illusions are greater when viewing large objects than small pictures of the same objects. (Yang et.al. 1999)

Figure 7. Upside--down T. The vertical line looks longer

People living in forests have little opportunity to see the horizon or great open vast space. As we will see later this illusion has also another explanation that is the difference between lower and upper visual field (Previc, 1990). In this context the experience of Colin Turnball with the BaMbuti pygmies is very interesting. These people live in the dense Ituri forest. Colin went with one of them to an open plane. They saw a buffalo grazing several miles away. The Pygmy asked Colin: "What insects are those?" Colin answered that these insects were buffaloes. The Pygmy roared with laughter and told Colin not to tell him stupid lies. He had no experience of seeing distant objects.

Figure 8. The illusion of objects not drawn in perspective is appearing bigger than objects in the foreground (Crone 1992).

Depth vision obviously has to be learned. We notice that the first who painted in perspective were the Romans. The paintings of the Egyptians and Mesopotamian cultures paintings have no perspective. In the Middle Ages this technique was forgotten till it came back in the renaissance. Brunelleschi from Florence gives a new impetus to the perspective. Alberti (1435) gave it a theoretical explanation.

Figure 9. Perspective construction of Alberti (1435). Parallel lines perpendicular to the plane of drawing converge to a vanishing point. Line drawn of a constant distance to each other parallel to the plane of drawing - figure a - becoming according figure b closer to each other in the direction of the vanishing point. (Crone, 1992)

The famous devils pitchfork is fooling us who are accustomed to look at a picture and trying to get it three-dimensional. Dergowksi (1969) found that people do not seek three-dimensional had less difficulty. We have a strong wish to look for three dimensions and initially do not notice carefully how the parts are related to each other.

Figure 10. The devils pitchfork

We see the world in terms of our cultural heritage and the capacity of our perceptual organs to deliver culturally determined messages to us (Highwater, 1981, 6-8). Indians and white people were looking at an old painting of a sailing vessel anchoring with a party of people on board. The Indians thought that it was a floating island covered with tall-defoliated trees and odd creatures with hairy faces.

We are always categorizing objects in the world round us. Always trying to give it a name. Eskimos have 16 terms for the word snow.

All these examples show us that a great deal of the forming of the image of the world around us is a learned process, sometime cultural factors playing a role. (Chandler, 1997)

The world outside us exists. It appears that we perceive the image of the world around us as it is there in reality. This is the biggest illusion of a human being. No, the world around us is constructed inside our brain. As we have seen the image is even distorted to our needs to survive and is not all the reality whatever that may be. We will never know what the world around us really is. We only not realize that we are making a caricature of it. We are biased by the way our brains are processing the image of the world on our two dimensional retina. Do not forget that we receive only a tiny part of the electromagnetic wave spectrum. The sunlight has its greatest intensity in the middle of our visible spectrum. We adopted our eyes to get the maximum of energy from the sun. We are still able to catch invisible waves of the spectrum by devices like TV, radio, fax, computer, radar infrared cameras etc, by transforming them to the spectrum of our senses. We have to realize that there will certainly more oscillations we are still not able to detect and to transform. What to think of telepathy and other until now mysterious phenomena we can’t explain and which are put aside by the scientific world in the category of metaphysics, black magic etc. Above this all we have to recognize that every individual is constructing his or her own unique image. Nobody perceives the same image. Everybody perceives his own rainbow!

The drawings of the Dutch painter Maurits Cornelis Escher is a remarkable example who one can be fooled with the three dimensions, as is illustrate in the famous Möbius Strip.

Figure 11. Möbius Strip II drawing of M.C.Escher. (With permission of the M.C.Escher Foundation, Baarn, The Netherlands).

Murch (1973) did a wonderful experiment. A group of persons were shown various animals and another group drawings of human faces. Then they were shown an ambiguous figure that could be interpreted as a man or a rat. The animal group said 100 % that it was a rat, whereas 73-80 % of the human face group saw the man rather than the rat, 81% of a control group not seeing prior images said the figure was a man.

The same type of experiment was done by the famous image of the young and the old lady. We construct a schema of a kind of mental template or framework, which we use to make sense of things. Related to application of schemata, is the process of categorization.

Categorization is a top-down process, which is involved in perception. Chandler (1997) gives a number of advantages of the process:

Elizabeth Loftus (1979) has demonstrated that even language plays a role in our brain when constructing an image. She showed two groups a film of a traffic accident and asked one group about how fast the cars were going when they hit each other. With the second group she changed the word "hit" in "smashed". This group gave higher estimates of the speed of the car. A week later the same observers were asked if they had seen broken glass. More than twice as many of those questioned with the word smashed seeing the (nonexistent) glass than those questioned with the word hit.

We are very selective in what we will perceive and what not. All of these principles of perceptual organization serve the overarching principle that the simplest and most stable interpretations are favored. In this context we cite an account of a man recovering his sight after 30 years:

We are also very good in filling gaps, because we know they should be there.

We are also strongly influenced by our state of individuality like: personality, cognitive styles, gender, occupation, age, values, attitudes, long-term motivations, religious beliefs, socio-economic status, cultural background, education, habits and past experience. But also our state of mind: goals, intentions, situational motivation and contextual expectance (Chandler 1997).

Current needs and social values can also influence perception. Two groups of children were asked to judge the size of coins. One was a poor group from a slum area in Boston and the other was an affluent group from the same city. The poor group over-estimated the size of the coins far more than the affluent group (Bruner and Goodman 1947).

The world is not simply and objectively 'out there' but is constructed in the process of perception.

Two illustrations will give us a good example of how we are fooled. We don't realize that the direction from which the light of the sun comes to us plays a dominant role in these illusions.

The visual areas of our brain have a built-in sense that the sun is shining from above.

Figure 12. Both figures are identical. To the left it looks if they are like eggs bulging out from the screen or paper, whereas to the right the are looking hollow, like cavities. (After Ramachandran, 1988)

10. We see edges of objects sharper than they really are.

This brings me directly to the remarkable facts in "seeing edges" more pronounced than they really are. The edges are areas that differ from one another in brightness. When a series of homogeneous stripes of different intensity are laid next to each other we notice something that is in conflict with the reality. Adjacent to each edge the brighter stripe looks brighter than it is really and the darker stripe looks darker thus enhancing the contrast at each edge and making the edge easier to see. These nonexistent stripes of brightness and darkness along the edges are called the "Mach" bands. First reported in the 19th century by the Austrian physicist, philosopher and psychologist Ernst Mach. He is also known for the number Mach in flying speed in relation to the speed of sound. What causes this enhancement?

When a receptor fire it inhibits its neighbor to fire, this is called lateral inhibition. The receptor D in our figure fires more than the adjacent A, B, and C because it receives less inhibition from the receptor E on the less illuminated side. Receptors on the dimmer side fire at the same rate all receiving the same lower level of inhibition from their neighbors. However receptor D fires even less because it is receiving more inhibition from receptor D on the brighter side. Thus our reception of edges is better than in reality. Another illusion is produced by lateral inhibition is the Hermann grid. The black dots on the white crossing do not exist. The same type of mechanism produces it as we have seen with the Mach band. At the crossing the whither stripes get more inhibition from the darker side than the stripes elsewhere.

Figure 14. The process of lateral inhibition producing sharper edges than they really are. (After Pinel, 1990)

Figure 15. The figure gives us a series of homogeneous stripe of different intensity, but adjacent to each edge the brighter strip looks brighter then really is and the darker stripe looks darker. The bands are called the Mach bands. It makes edges sharper than they really are. (Taken from the textbook of Pinel, Biopsychology, 1990, fig 7.13 pag. 184).

Figure 16. Blurred lines become sharper when viewed in the peripheral visual field (After Galvin, 1997)

A very strange effect was described by Galvin et.al. (1997). They demonstrate with an experiment that we see blurred edges in our peripheral visual field as a sharp edge. This they call sharpness overconstancy. Maybe evolution has created this effect to draw attention to objects in our peripheral visual field. Look for your self by viewing the blurred edge. Hold the figure about 30 cm from your face and fixate your eyes to the outer edge of the page and judge the left edge in the center of the square field and then fixate the edge. You will see the edge sharper when it is in your peripheral whereas in your foveal vision it is blurred!

Within to degrees of our visual field the image is sharp, so it is necessary in order to have a clear image of our world that we must direct this part of the retina to our image. This eye movement is called a saccade (The word is derived from the French word saccader meaning to jerk). We make 250.000 of this movement's daily. Even in our dream during the rapid eye movement sleep we are executing this movement. The movement is exceedingly quick: 700 degrees per second. It takes 50 ms to initiate a saccade and it is only possible to initiate a next saccade after 200 ms. It implicates that we can make only 4 saccades per second. Vision is depressed just before and during the saccade.

During an eyeblink we lose sight of the visual world for more than a tenth of a second without perceiving the discontinuity. The posterior parietal cortex updates continuously information about the nature and structure of visual objects in the ego-centered space. It is kept also informed about eyeblinks the posterior parietal cortex is related to working memory necessary for maintaining a continuous image of the environment despite the 0.1 s loss of visual input during each eyeblink. (Hari et.al. 1994)

Figure 17. Before every eye movement (saccade) to a target the brain needs 50 ms preparation time.

To get the eye on the exact spot the eye movement is compensated with a counter movement to correct the overshoot.

In our western culture we are reading from left to right and from up- to bottom side of the page. We see about 4 words in focus and have to make 3 saccades per rule.

To check for yourself, if you are blind during a saccade. You have to look in a mirror and fix your view alternatively to your left and right eye. You don’t see any movement of your eyes at all. But ask someone who is standing next to you, if he had seen that your eyes have moved during the switch. His answer is to your astonishment: YES.

Another example how little we know about our entire unconscious movements and ourselves.

When the eyes are fixed on a target there are continuous unconscious small movements of the eyes at 30 and 150 cycles per second. These small movements are essential for continuous vision. Objects that are totally stabilized on the retina will disappear. Krauskopf has done an experiment to show this effect. A red circle with a smaller green circle in the middle. The borderline was moving as fast as the small movements of the yes. The relative movement and image was not anymore present. So the eye stayed fixed on the green circle. It disappeared only a red circle was seen. The receptor cells for the green cells were oversaturated and ceased to fire. (Gilchrist, 1979)

Not only saccadic movements are executed but the eyes are also possible able to follow a target that moves (smooth pursuit movements). These movements are necessary for visual discrimination of moving objects because they stabilize the image of the target on the fovea by matching eye velocity to target velocity. The eye is anticipating the target trajectory. Deficits of these movements have shown that a network of frontal and posterior cortical areas is involved (Heide et.al., 1996)

Braun et.al. (1992) showed that dorsolateral lesions are more severe for the saccadic movements than frontal lesions. Patients with dorsolateral lesions indicated that the earlier steps of saccade preparation appeared to be impaired i.e. the utilization of information about location and appearance of the target.

A great number of brain areas are involved in this complicated eye movement.

A saccade is generated in the brain stem. A special nucleus (pontine reticular formation, PPRF) discharge with characteristic response patterns during saccade. The most important structure is the superior colliculus. Microstimulation of a given point in the superior colliculus will cause a saccade that brings the image of the corresponding point of visual pace on the central retina. The frontal eyefields are involved in generation of a saccade as is the cerebellum.

FEF nerve signals to caudate nucleus (basal ganglia) then on to the substantia nigra. This nucleus sends signals to the superior colliculus. Normally the superior colliculus is inhibited to generate a saccade by the inhibitory influence of the subcortical substantia nigra. Now something very remarkable happens. When the caudate nucleus (part of the basal ganglia) is excited it sends inhibitory signals to the substantia nigra. This prevents this nucleus to prohibit the superior colliculus. The superior colliculus is now freed from the inhibition (disinhibition) and can give signals to the frontal cortex to generate the saccade.

Figure 18. When the superior colliculus is freed from the inhibition of the substantia nigra saccadic movements can be executed. A good example of that the forbidder is forbidden to forbid.

Cells dealing with vertical saccades and horizontal saccades are separated from each other. Vertical saccade cells are concentrated within the callosally connected patches of the frontal cortex and horizontal saccades with the callosal free zones.

Vertical saccades are slower than horizontal saccades. Oblique saccades have both vertical and horizontal components.

The parietal cortex is also involved in the saccadic eye movement. The parietal cortex anticipates the retinal consequences of eye movements and updates the retinal coordinates of remembered stimuli to generate a continuously accurate representation of visual space (Duhamel et.al.1992).

Figure 19. Brain areas involved in the eye movements

Gnadt et.al. (1990) studied eye movements to the remembered location of visual targets, which have disappeared. The brain must hold some form of spatial representation of the targets, which are not dependent on the physical presence of the target.

When reading a difficult text the eye can make an unconscious backward saccade in order to get a better understanding of the text.

We have also a dominant eye. It is easy to find out your self. Put your thumb and index finger together and look through the hole at 30 cm distance of your eyes to a certain object in the background. Close one eye; when you still see the object it will tell you that this is the dominant eye. When you close the dominant eye and look with your other eye you will see that the object vanishes and the object is shifted.

Sometimes there is a rivalry between signals coming from left and right eye. They have a different visual relating to the same part of the visual field. As we have seen the left side of the head receives input from both eyes but sees only that part of the visual field to the right of the fixation point. Two conflicting inputs are in conflict with each other if you do not see the two inputs superimposed but first one input then the other and so in alteration. Good example is the Neckar cube. A drawing spontaneously reverses in depth. The Swiss naturalist and crystallographer L.A. Neckar in a letter to Sir David Brewster described it in 1832. Neckar discovered it while looking at rhomboid crystals with a microscope and drawing them: the drawings switched in depth and no longer seemed to compare with the crystal as seen with the microscope (Gregory, 1987). By imaging the Neckar cube we can not obtain this Neckar effect.

Figure 20. The Neckar cube.(1832) Changing every 3 second in depth vision. When the ribs at the back are obscured the illusion is not taking place.

Sally Duensing and Bob Miller (1977) have done an experiment to illustrate this binocular rivalry. Viewing in a well-placed mirror, one eye looks at a person’s face and the other eye sees a white screen to the side. If the viewer waves his hand in front of the white sheet of paper the image of the person is disappearing. The brain has captured the attention of the waving hand.

Figure 21. Example of binocular rivalry. A mirror placed that one eye can look at another person's face, in front of him, while the other sees a waving hand for a white screen to the right. (Crick, 1994)

Leopold and Logothesis (1996) suggest that rivalry occurs at several levels in visual areas (V5, V4 and IT) Under certain circumstances we will see a continuous struggle between regions dominated by both eyes input and regions dominated by the other (Wolfe, 1996). Why do we see only one of the ambiguous images one at a time? Our brain can simultaneously analyze two conflicting representations. A selection process ensures that we only are aware of one (Leopold and Logothesis, 1999)

I have not yet found in the literature experiments to demonstrate conflicting images on lower and upper visual field..

The processes we just described are complicated processes involving signaling from higher visual areas to lower areas (top-bottom), voluntary decisions focusing our attention, whereas bottom- up there is no conscious control such as the brain's involuntary mechanism for resolving between conflicting information from of information it receives. Bottom-up influences are responsible for certain illusions in which the brain is tricked perceiving something distinctly different from the image received from the retinas. As with the Neckar cube, the stimulus may be the same but one sees in one way or another (Baringa, 1997).

We see and we not see things! People are thinking that they can see a scene its entire structure in great detail. Attention can be allocated on a few items implies that only a few changes can be perceived at a time any time.

Observers never form a complete detailed representation of their surroundings. (Rensink et.al. 1997)

How long does it take for the human visual system to process a complex natural image? According Thorpe et.al. (1996) the visual processing needed to perform a highly demanding complex task can be achieved in less than 150ms. Preknowledge about the possible location leads to faster and more accurate responses to visual aspects.

Attention consists of partially concurrent processes: a fast effortless automatic process that records the cue and its neighboring events and a slower effortful controlled process that records the stimulus to be attend and its neighboring events.

Attention consists of partially concurrent processes: a fast effortless automatic process that records the cue and its neighboring events and a slower effortful controlled process that records the stimulus to be attend and its neighboring events.

Temporal trigger searching attention shift in attention can alter pattern of activity in the visual areas without any change in activity in the retina or other earlier visual pathways. By filtering out irrelevant signals and adding information about objects whose presence is remembered or inferred the cortex creates an edited representation of the visual world that is dynamically modified to suit the immediate goals of the viewer.

Figure 22. Attention to the red object (closed dots) gives a response to the red bar in the receptive field. When attention is given to the green object (open dots) in the same receptive field the response to the red bar drops. (After Moran and Desimone, 1985)

Desimone and his student Moran did a very interesting experiment. A monkey looked at two objects one red and the other green were within a receptive field. When attending to the red object the cells in the V4 area (color area) gave a good response. Then the animal was asked to attend the green lying in the same field, the red neuron was silent, very surprising because the red object was still in the same field. It was though the red had been filtered out by the animal's attention. The choice of how to direct attention influences the responses throughout the visual-processing pathways. It takes 150 to 300 millisecond to switch attention in neurons in V4 (Desimone and Moran 1985, Barinaga , 1997).

Moran and Desimone (1985 ) trained monkeys to attend stimuli at one location in the visual field and ignore stimuli at another. When both locations were within the receptive field in area V4 of inferior temporal cortex the response to the unattended stimulus was dramatically reduced. This filtering is an important mechanism in order to identify and remember properties of a particular attended object out of many that may be represented on the retina.

Chelazzi (1993). Visual searches for a face in a crowd memory interacts with attention. Chelazzi et.al. (1993) presented monkeys with a complex picture to hold in memory. They tested the neurons in the inferior temporal cortex. After a delay they were presented to 2-5 choice pictures and were required to make an eye movement to one that was the same as the first picture that was given to them. About 90-120 milliseconds before the onset of the eye movements, response to non-targets were suppressed and the target dominated the neuronal response. It suggests that the inferior temporal cortex is involved in selecting the objects to which we attend and fovaete.

Also in other high-level visual area in the cortex attention is reflected in part by suppression of neuronal responses of ignored objects.

The pulvinar of the thalamus contains neurons that generate signals related to the salience of visual objects. The pulvinar has enlarged during evolution. Choosing relevant from irrelevant visual stimuli. During a saccadic movement the cells do not respond the selection of salient targets and filtering of nonsalient distracters (Robinson and Petersen, 1992).

All these examples I have given in this chapter are demonstrations how we are constructing images from the world around us. In the next chapter I will go in the brain and show how all the signals from the outer world are processed. A purpose writing this chapter is to convince the reader how complicated the machinery is necessary to form an image of the world around us. What I especially want to emphasize is the necessity for our existence to separate relevant from irrelevant data. We are constantly bombarded by all sorts of vibrations and in order not to become utterly confused and insane we need to deal with these streams of information in such a way that we can transform the perceived world into actions that will keep us going!

Sometimes the images we are receiving are too weak to enter consciousness. Marshall and Halligan (1988) reported a case of a woman with a severe neglect who explicitly denied any difference between the drawing of an intact house and that of a burning house when the features relevant for the discrimination were in the neglected side. (Berti and Rizolatti,1992). But when she was asked in which house she would prefer to live she indicated the house that was intact.

Focal attention is apparently not necessary for processing visual stimuli in higher brain areas. It is possible that we are able to process information to a semantic level outside the focus of attention.

Without the attention the representation is too faint to reach conscious level even when the stimulus is processed on a semantic level. Spatial perception does not have to be intact to activate semantic processing when only partial information of the world is available.

A patient with a right hemisphere damage was shown drawings with a global form such as a geometric figure, which is composed of smaller (local) dots, circles or letters. She gave accurate verbal reports of the global structure of these stimuli, yet when required to cross out the smaller subfigures she only cancelled those on the right of each global figure. Conscious perception of the whole does not automatically lead to visual awareness of all the parts thereof. "Seeing the forest but only half of the trees?" is the title of the article of Marshall and Halligan (1995)

Driver et.al. (1992). Are figures segregated from their background preattentively or whether attention is first directed towards unstructured region of the image? According Driver et.al. information, which is neglected and unavailable to higher levels of visual processing, can nevertheless processed by earlier stage in the visual system concerned with segmentation. They have studied a patient with left neglect, with no loss of left visual field, he had an attentional deficit. He retains intact figure-ground segregation despite his left neglect.

Treue and Maunsell (1996, 1997) have shown by their experiments that attention can modulate vision. Without selection we would be inundated by information. Only a small fraction reaches awareness. Modulation occurs as early in the cortical hierarchy as the level of the middle temporal visual area.

According certain theories the visual system decomposes the visual scene into features that are processed in parallel subsystems. They act independently before focal attention integrates their output. Kubovy et.al. (1999) proposes a new paradigm (gestalt detection) that the modules that process color and form are not independent but interact during the preattentive processing of feature -dependent information. They are synergistic when the information they receive is consistent, they are antagonistic when ten information they receive is inconsistent. Their data show that the integration of feature dimensions occurred without the help of focused attention. This is in contrary with the early processing theories of Treisman and others that focused attention is necessary for feature integration. What is the role of focused attention? It is necessary when an inconsistency exist in the environment. The interaction between form and color is also shown in the neuroanatomy of the visual cortex.

The patient of Rapcsack (1988) was re-examined in using the paradigm of Shelton et.al. (1990). By Mennemeier et.al. (1992). The study suggests that attentional processes are mediate by independent neural circuits.

Attentional mechanisms are more than a simple left-right dichotomy. Attention may be oriented in three dimensions of space horizontal vertical and radial. The patient of Rapcsack had neglect of inferior vertical and left horizontal space. The studies are demonstrating that neglect occur in multiple spatial dimensions and provide evidence for a three-dimensional attentional system in humans.