perceiving

1. perceiving By Dr. Diyar Hussein TahirM.B.Ch.B.-F.I.C.M.S.Psych. Department of psychiatry, College of Medicine, Hawler Medical University.

2. *Higher mental processes (HMP):Are ways in which we adjusts effectively to the all events in the environment in a consistent & integrated fashion. They include thinking, learning, perceiving & remembering. The processes are collectively referred to as ‘higher’ forms of behaviour because: 1-The man’s superiority over animals is in such forms of behaviour. 2- They are held to be associated with ‘higher’ nervous system. - HMP provide man with a continuity of his experiences; where they link his past experiences with those of present & those which are projected into the future. So in the same way as vision & smell are described as distance receptors, we can say that HMP are ‘time’ receptors. HMP are means of adaptation to the Environment by: -Reacting to stimuli -Organizing these stimuli -Synthesizing them in creative thinking -Then retaining them in such a manner that subsequent behaviour can be altered.

3. *Perceiving:Means being aware of the meaningful sensory input. It depends on the: 1- Sensory data from the environment. 2- Organism that operate on the environment. 3- Selecting activity of the surrounding information. -The major functions of the perceptual system are: 1-To determine which part of the sensory environment to attend to. 2-To determine where objects are. 3-To determine what objects are. 4-To abstract the critical information from these objects. 5-To keep the appearance of these objects constant, even though their retinal images are changing.

4. *But perception is not just a direct simple awareness of the external stimuli: This can be understood for e.g. by Seeing a red colour, which can happen by: 1-Stimulating an intact retina by a radiant energy in a wavelength over the effective range of visual spectrum. 2-Stimulating the retina electrically. 3-Striking the eye sharply. 4-Disturbing the visual center of the brain by a blow on the back of the head. 5-Looking at a red light for some time in a darkened room, then turn the light out, where the experience of red will persist after the original stimulus has gone. This called Positive after image, which will be replaced soon by a Negative after image (in this case green; the complementary colour to red) -Also if we stare fixedly at a red patch on a grey background, the border area between the red & grey is seen as greenish hue which is again not the result of an actual physical wavelength stimulus. This called colour contrast.

5. *Perceiving & constancy of the external world: Perceiving plays it’s part in adaptation by allowing us to maintain an external world that is constant & permit us to inhabit a stable world, such that even when the stimuli are imperfectly presented to us we are still able to perceive them in what we know them to be. The Perceptual constancies begin to develop as early as 6 m. This can be shown through the following phenomena: 1-Form constancy: We perceive objects as being constant in shape although they stimulate us in different ways, for e.g. if we look to a coin on a table from different angles, we will see it as circular although the actual shapes that it formed on the retina are elliptical . 2-Size constancy: If we hold the coin at arm’s length then bring it close to our eyes, we are increasing the size of the retinal stimulus … yet the coin appears in our mind to have the same size. 3-Brightness constancy:If we take a black object and increase the illumination on it until the actual amount of light reflected from it is greater than from a similar but white object in shadow….. The black object is still seen as black & the white as white.

6. 4-Perceptual constancy during movement: If we turn our head sharply, the stimulus pattern is such that there should be a blurred movement in the visual field rather like the picture from a swung movie camera; however, the environment is still remain constant. This is achieved on the basis of experience (by learning),but there is evidence that some parts of the process may be due to inherent factors. Loss of the perceptual constancy: The psychiatric disturbances which occur in psychotic disorders or after taking hallucinogenic drugs as Lysergic acid diethyl amide (L.S.D.) appear to involve a basic loss of the perceptual constancy in the form of: - Apparent movement in the environment - People & room seem to change their shape or size - Walls may bulge backwards & forwards - Pronounced negative after image appear - Colors seem enhanced in brightness -Any type of hallucination may occur also.

7. *The Gestalt school (form school) approach to understand perception : A group of German psychologists demonstrate the significance of pattern (or form) in perceiving. This approach reacted against the Associationist group view which analyzed perceived events by splitting them into bits or components. The G.S. disagreed for example that a melody is the result of the sum of all it’s constituents as rhythm, pitch & loudness, and they showed that the melody can be played in different keys, & it’s tempo & rhythm can be changed but in spite of all these changes it is still recognized as the same melody, because it possesses ‘wholeness’ or form quality.

8. The G.S. principles for perceiving forms: 1-Principle of proximity:It demonstrates that those elements of a stimulus which are closest together will be perceived as one group or gestalt. So in the 2nd figure the arrangement in columns become more obvious than the rows, because the dots in the columns are closer together than in the rows. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1

9. 2-Principle of similarity: When a no. of elements present, those that are similar tent to form groups. So in the lower figure we tend to see the pattern in rows rather than columns, because the lines are now organized together as one group and the dots as another group according to similarity principle. _ _ _ _ _ _ . . . . . . _ _ _ _ _ _ . . . . . . _ _ _ _ _ _ . . . . . .

10. 3-Principle of closure:Those forms which are closed tend to be perceived as units. So in the next figure the 6 lines are seen as 3 pairs of lines on the basis of proximity, but when an extra horizontal lines are added, the original pairing is destroyed, in spite that it is still present, infavour of a pairing between the more distant lines, & those forms which are closed tend to be perceived as units (in this e.g. rectangles) 1 2

11. 4-Principle of goodness of forms:Those forms which have better contour or form tend to be perceived as units. So in the 2nd figure although the original shapes can still be seen, the figure is more readily received as an overlapping circle & trapezoid. This occurs because the circle & trapezoid have better forms than the previous 2 shapes 1 2

12. * The significance of experience & the effect of illusion in perception: Where what a person have learned previously has an effect on what he perceived. … For e.g. • In the lower figure we see 3 disconnected lines, but if we rotate the figure 90 degree to the right we can see that the figure now becomes a block capital ‘E’. But anyone who was not familiar with the English alphabet would be unable to perceive this letter, because he hasn't learned to do so.

13. Also….. The capital letter ‘E’ is perceived although only half of the stimulus is present, but this is sufficient for closure principle to give the impression of the complete capital letter ‘E’ that present in our mind from the past learned experience. This shows that our awareness is sometimes based on illusion.

14. In the Muller-Lyer illusionthe first line appears distinctly shorter than the second one in spite of that they are equal. This explained in Gestalt term by closure effect where the first line is limited by 2 arrows which tend to shorten the whole figure & hence the enclosed line. • Perceiving movement:when we see moving pictures in cinema we are experiencing illusory or synthetic movement, where the actual stimulus is a sequence of still pictures, eachrepresenting a phase of the movement, & project at a speed of a bout 16 frames per second, below this projection speed we tend to see jerky pictures which destroy the illusory movement. This illusory movement effect has been studied as phi-phenomenon , which studied experimentally in it’s most elementary form by a simple apparatus include 2 small lights with a few inches apart. Light A is switched on for a brief period & an instant after it is switched off, Light B is switched on briefly. If the time-interval is correct, we will see the light move from source A to B. Similar thing occur in neon advertising signs. A B

15. *Perceptual set:Indicate the perceiver readiness to respond to certain organizations of stimuli. Where it is found that needs & emotions of the receiver determine what is perceived…. E.g. In an experiment in which they were asked to identify certain vague objects, hungry students tended to see more the edible things. Also the anxious person is likely to perceive events & situations as being fearful or threatening. *The perception of pain: - Perceiving pain is of a biological or survival value. - Patients from different ethnic groups responded differently to pain, where patients of Anglo-Saxon origins usually did not express their pain publicly, whereas Jewish & Italian patients would cry out to seek help from their family or from hospital staff. - When anxiety is increased the experience of a standard pain stimulus is increased, & when anxiety reduced it reduced. - The analgesic effect of morphine is greatest when anxiety is high (as in ISHD) & may not be detectable if anxiety is absent (as in some slowly growing carcinomas).

16. *Attending: - Is the process whereby we focus on certain aspects of a situation, & it is based on the perceptual sets. - We may attend to events without our conscious control, others become the objects of our attention by choice. But Sudden or unexpected stimuli, Intense sounds, Bright colors, & Repeated stimuli, all are ways of securing our attention & so exploited by advertisers.

17. *The range of attention:Normally there is constant shifting of our attention, & at any time we can be fully aware of certain events & only dimly aware of others. E.g. As we read we attend to the print, but if our attention wanders we may become aware of other stimuli such as a ticking clock, sounds outside the room or even the pressure of our clothes, where the original attention to the book was focal & the other stimuli were marginal until the centre of attention shifted. Also if we look steadily to a simple drawing of a cube, at one time the side next to us appears near but this suddenly changes that it appears far from us. Thischange will occur no matter how hard we concentrate our attention !!! This fluctuations of attention can be regarded as part of our mechanism for ‘searching’ or ‘scanning’ the environment.

18. *Span of attention: It means the amount of informations which we take-in during exploring a complex stimuli, & it determines how quickly we can perceive. The normal observer can accurately attend to about 7 dots presented to him for 1/5 of a second. It appears that 10 dots presented in an unpatterend fashion are outside the span of attention. But the span of attention can be increased if the dots organized into patterns, as on the basis of proximity or closure, i.e. organization of the stimuli allows the observer to perceive more material than his basic capacity for attention.

19. *Images: In perceiving we require in addition to the ability to deal with the immediately present environment, the ability to bring our past experience to bear on the problem. So: Imagingis the process whereby we use images of objects which are not immediately present but which have been perceived at some previous time, e.g. describing your morning breakfast. WhileImaginationItdiffers in that it is independent of any direct previous perceiving, e.g. describing breakfast of men from the outer space. It is important for artists, writers, & other creative thinkers. There are individual differences in imaging regarding: 1-Intensity: some persons report images as real as the originally perceived objects, while others obtain no images at all. 2-Mode: most people have images which combine a no. of different modalities, but some are particularly prone to use visual images, others auditory, some even taste images

20. Eidetic images: Is highly vivid images in whatever modality. It occur more frequently in children, in which the child with strong visual eidetic imagery can look at a complicated picture and give accurate responses to questions about details after the picture is taken away. Imagery of this sort produces a large spans of attention; for e.g. there were a man with ‘photographic mind’where he could look for a few minutes at a collection of numbers in 4 columns of 13 numbers, then he could reproduce all the numbers in a correct sequence, could call out the numbers up, down, & diagonally from any point of the array. But while students may envy the gift of eidetic imagery, it is proved to be a drawback in creative thinking which need good imagination rather than imaging, where the person might not cope with a simple abstract ideas because they could not be visualized as images.

21. *The importance of getting information from the environment for normal perception & adaptation: In everyday life our perceptual processes operate smoothly, but if there is loss, decrease or change in the capacity for getting information from the environment, our ability to adapt is reduced as in following situations: 1-Blindness:in which other means rather than visual of getting information have to be adopted, & here the blind person can be trained to compensate by exploiting auditory or tactile sensations. But….Recovery of sight after blindness although this is usually considered as a dramatic relief, the patient may have difficulty in adjusting to this new sudden high sensory input, & he will need time for adaptation. For e.g. there was a case of 50 years old patient blinded in infancy, showed distress when his sight was restored, where he was terrified to move in traffic although he had previously moved about in the streets confidently, he became depressed & preferred to be alone in the dark.

22. 2-Sensory isolation: In an expt., a group of paid volunteers were put in isolation in an air-conditioned box. where they lay on a bed with arms & hand restrained in cardboard sleeves, their eyes covered with translucent goggles & wearing headphones to mask any sound. After some hours of reduced sensory input the persons found it difficult to concentrate their thinking & developed extreme desire for some sort of sensation, & even move about in order to satisfy this desire. After a while they were unable to discriminate between sleeping & waking. Most subjects were unable to stay in this situation for longer than 72 hours, but in those who persist, hallucinations & delusions developed. Similar psychological experiences may developed in: solitary confinement prisoners Arctic explorers shipwreck survivors single-handed sailors

23. 3-The significance of normal natural environment for normal development: - In an expt. they raised a group of rats ( experimental group) in a psychologically restricted but biologically adequate environment ( in a small cage with no problems to solve & with no experience of pain), while a control group was reared in a free environment in which there were plenty of obstacles to overcome. The results showed that the experimental group had a persisting inferiority in problem-solving behaviour i.e. the rats from the restricted environment were less intelligent. - Also, animals raised in darkness will suffer from permanent visual impairment, & animals raised with a patch over one eye will become blind in that eye. But adult animals do not lose vision even when deprived stimulation for long period, indicating that there is a critical period early in life when lack of normal stimulation will produce deficiency in the innate perceptual capacity.

24. *Clinical implications in perception: In any sensory defect & when a sensory apparatus is damaged or partially destroyed, the impairment of perception may not be an accurate reflection of the amount of sensory damage, e.g.: 1-Hemianopia:here destruction of nerve cells in the visual cortex of the brain can render ½ of the visual cortex apparatus inactive, so the visual field is cut in half vertically. Surprisingly the patient may not report this as a handicap to his everyday activities as he is able to readjust or compensate it. Gestalt psychologists investigated such patients to demonstrate their principle of closure in perception: They presented an incomplete circle to those hemianopic patients, but the patients perceived the whole figure & in ‘complete circle’ when the amount presented was sufficient to determine the nature of the whole figure, this is called closure after defect. Similar thing occur in: - Deafness affecting only certain sound frequencies. - Tactile sensation disorders. So the patient’s report that he can see, hear or feel properly does not necessarily mean that his sensory apparatus is intact. For this reason a number of special tests for sensory function are used in medicine.

25. 2-Phantom limb: this is a more elaborate instance of the tendency of closure after defect, where following amputation of a limb, the patient may continue to experience a realistic sensations in the missing limb for a time (even for years), where the patient feels that his limb is still there, & for e.g. when a patient who had an amputated arm at the elbow walked up to a wall with his stump outstretched until the stump touched the wall, he will feel that the phantom hand & forearm had gone through the wall. This odd phenomenon is related to the ‘perception of the bodily self’ or ‘body image’ which derived from sensations in the muscles, tendons, joints, & balancing mechanism from vision, hearing, taste, touch & smell. *Tests of perceptual function: The perceptual disturbance (sometimes referred to as disturbance of gestalt function) leads to inability to organize stimuli in a meaningful fashion, which can be discovered by asking the patient to do one of the following tests: 1-Copy simple designs as an intermingle 2 pentagons. 2-Reproduce patterns using match-sticks. - A patient showing disturbance of gestalt function is unable to do such simple test accurately.

26. 3-Ishihara test for colour blindness: The patient is shown a series of cards each of which contain a mosaic made up of hundreds of little dots of different colors. Embedded in the mosaic he may see a number which he should report to the examiner. This number is perceived on the basis of the principle of similarity. Some of these cards contain two numbers, for e.g. no. 5formed by dots all of the same colour, & no. 2 formed by dots of the same brightness. The normal person will reports the 5 & 2 While the colour defective eye personwill reports just the 2, as he has come to use brightness discrimination to compensate for his poor colour discrimination. People who suffer red-green colour deficiency have trouble perceiving the number within this design.

27. THANK YOU