Perception Сompleted student 1 year Faculty SSP social

Perception Сompleted student 1 year Faculty SSP (social educator) Julia Burlachenko

Constancy refers to how our perception of objects remains the same despite changes in their image on the retina. Constancy is seen in the perception of a number of different properties of objects such as size, shape, color, and orientation. Despite constancy's great importance and prevalence across much of visual perception, there still no widely agreed upon explanation of it. There is, however, great agreement that constancy is based in part on the observer using appropriate contextual cues in the environment.

Perception of motion The perception of motion has been the subject of much research. The mystery lies in how perceived movement cannot be accounted for by the movement of an object's image across the retina. If that were so, movement of the observer, or eye movement would lead to perceived object movement. Another phenomenon of motion perception that cannot be fully explained by sensory processes involves saccades, which are rapid directed eye movements. Evidence suggests motion perception can be partially explained by our apparently automatic use of numerous specific spatial and sequential relations between stimuli. In addition to contextual environmental factors, specific visual receptor cells that detect different types of movement such as up and down have been discovered. Despite this knowledge, many questions about the exact mechanisms of motion perception remain unanswered.

Form perception is what enables us to identify objects and distinguish them from each other. Rather than a loose grouping of apparently separate stimuli, we see the world as organized with interrelated objects having definite shapes and forms. And as with many other perceptual phenomena, the light projected onto the retina from objects cannot account for our visual perception of the world. It seems perceiving form involves certain organizational principles, many of which were discovered by the Gestalt school of psychology. These rules or principles illustrate our tendency to organize and group separate elements of the visual world. The perception of form can be said to result, in part, from characteristics of the nervous system, as well as learning and experience. Yet there is no single theory of form perception that can fully account for the ability to perceive form. Nor is there a general principle that can pull together the many different types of form perception.

Depth perception This entails perceiving the three-dimensionality of the world and objects. This clearly involves more than the nature of images sent to the retina since the retina has a two dimensional surface and images projected onto it are two-dimensional. In the 1800 s researchers discovered that our binocular vision greatly aids depth perception. Binocular vision refers to having two eyes that are at slight distances from one another, so that each receives a slightly different perspective of the object or scene being focussed upon. . In addition, most environments have common patterns corresponding with varying distances that provide visual clues about space and depth. Such clues include blocking of a far object by a near one, increasing haze with increasing distance, perspective, and shadow. In sum, binocular vision and environmental cues can account for many aspects of depth perception. In addition, based on research with animals and human infants too young to have had experience with depth perception, it appears that humans and various species of animals are born with some innate visual mechanism to perceive depth.

Illusions are misperceptions of stimuli, where what is perceived does not correspond to the actual dimensions or qualities of the physical stimulus. Geometrical illusions usually involve the misperception of the direction or size of parts of figures. The mechanisms that produce many types of illusions are as yet not understood, but they seem to involve the misapplication of perceptual phenomena like constancy. Illusions are natural, occurring regularly and following regular rules. Over the last century a number of theories have been proposed to account for perception. Each theory, however, has encountered difficulties in accounting for some of the above-discussed phenomena of perception. And most perception researchers today do not adhere to one theory, instead they believe those aspects of theories that have some experimental support, or that seem most logical and sound.

Classical theory What is sometimes referred to as classical theory is usually associated with Hermann von Helmholtz who believed perception results from a process of unconscious inference about what the stimulus affecting the sense organs is most likely to be. He thought these unconscious inferences are formed by past experiences and learning, and they are unconscious because people are clearly not aware of making them.

Psychophysical or direct theory This theory as put forth by J. J. Gibson holds that perception may be fully explained by the properties of the stimulation we receive from the world interacting with our sensory capabilities. Characteristics of scenes and events in the physical world may give sufficient information for the nervous system to be able to specify them. Thus, there is no need to posit unconscious mechanisms of inference as put forth by the Helmholtzian theory, or higher order organizations of stimuli as proposed by Gestalt theory.

Modern sensory physiology This theory proposed by E. Hering and E. Mach believes the structure of the nervous system may fully explain at least some perceptual constancies as well as depth perception. E. Hering also proposed that there may be visual receptor cells organized into certain functional patterns that provide color sensation. And in fact these functionally patterned receptor cells have been found. These findings have strongly influenced current views of color perception, and the study of perception and sensation in general. It is still unknown, however, whether similarly organized receptor cells may exist for, or contribute to, perceptual phenomena such as the constancies and illusions. But their demonstrated existence may indicate that many perceived qualities of the physical world are based on such specific sensory mechanisms. Some of the more recent theoretical and research developments fall within the areas of emotion, neuropsychology, ecological psychology, and artificial intelligence.

Emotion Reflecting a trend across psychology as a whole, there has been a renewed and increased interest in how emotion influences perception and attention. This research investigates such questions as how emotion influences the focus and duration of attention, how quickly the emotional meaning of various stimuli can be processed, and whether individuals attend to positive and negative stimuli in different ways. Unlike most past research on perception this evolving area often researches socially meaningful perceptual stimuli, such as the perception of emotion in facial expressions and in vocal tones.

Neuropsychology Neuropsychologists study changes in thinking due to brain injury, and use brain imaging techniques such as magnetic resonance imaging (MRI) and positron emission tomography (PET) scans, to examine the activity of the brain while performing highlevel mental tasks such as problem-solving. A number of their findings have challenged explanations of perception based on behavioral studies. And improvements in brain imaging techniques hold the promise of shedding even more light on the neural basis of perception.

Ecological psychology attempts to specify the unchanging and limiting aspects of perceptual stimuli in the environment. They also stress how the nature of perceptual stimuli supports perception. This approach is most closely associated with the psychologist J. J. Gibson.

Artificial intelligence This is an interdisciplinary field combining research and theory from cognitive psychology and computer sciences. It focuses on the development of artificial systems, such as computers, that show thinking processes similar to humans. This approach believes that for a complete explanation of perception it is necessary to divide it into three levels of analysis: 1) hardware, or its physiological aspects, 2) algorithms for operation, or what the processes of perceiving are, and 3) theory of the task to be performed, or what are the qualities of our environment that enable perception. It is hoped that these divisions will serve as an important intellectual tool and aid our understanding of perception. Perception is a field ripe with unanswered questions that continues to fascinate researchers who may greatly benefit from new technologies and new perspectives. Indeed, recent technological advances in the measurement of eye movements (saccades) have made their study much easier for researchers interested in changes in the focus of visual attention.