How do perception and sensation interact

Myers - Chapter 7: Perception


  • 7.1 Basic principles of sensory perception
    • 7.1.1 Transduction
    • 7.1.2 Thresholds
    • 7.1.3 Sensory adaptation
    • 7.1.4 Perception set
    • 7.1.5 Context Effects
    • 7.1.6 Emotion and Motivation
  • 7.2 See
    • 7.2.1 Light energy input
    • 7.2.2 The eye
    • 7.2.3 Visual information processing
    • 7.2.4 Color vision
    • 7.2.5 Visual organization
    • 7.2.6 Visual interpretation
  • 7.3 listening
    • 7.3.1 Stimulus input sound waves
    • 7.3.2 The ear
  • 7.4 Other important senses
    • 7.4.1 Sense of touch
    • 7.4.2 Pain
    • 7.4.3 Sense of taste
    • 7.4.4 Sense of smell
    • 7.4.5 Position and movement of the body in space
  • 7.5 Excursus: Extra-sensory perception - perception without sensation?
  • 7.6 Chapter review
    • 7.6.1 Questions of understanding
    • 7.6.2 Key Terms
    • 7.6.3 Further German literature


Basic principles of sensory perception

sensation is the process by which our sensory receptors and the nervous system receive stimulus energies from the environment and represent them. perception is the process by which we organize and interpret this information. Although for analytical and descriptive reasons we see sensation and perception as separate from one another, in reality both are part of a continuous process. The data-driven processing is the sensory evaluation that starts at the input of the information when it flows from the sensory receptors to the brain. Conceptual processing is an evaluation that starts in the brain and then goes back to lower levels; the information is filtered based on our experience and expectations. This then creates perceptions.

Each species is equipped with the sensitivity that will ensure its survival and survival. Psychophysics is the scientific investigation of the connections between the physical characteristics of stimuli and the way in which we experience them psychologically. Our absolute threshold for each stimulus is the minimum stimulation required for us to be aware of that stimulus 50% of the time. The Signal detection theory shows that our personal absolute thresholds depend on the strength of the signal, but also on our experiences, expectations and our own motivation and vigilance. Our Difference threshold (also referred to as a noticeable difference) is a hardly noticeable difference that we recognize in 50% of the cases. The Weber's law states the following: In order for two stimuli to be perceptually different, they must differ by a constant ratio (such as a 2 percent difference in weight) and not by a constant difference. Tests on the priming effect and other experiments show that we can process some information from stimuli that are below the absolute threshold for awareness. But the limited conditions under which this occurs would not enable unscrupulous opportunists to seduce us with subliminal messages.

The sensory adaptation consists in the fact that we are less sensitive to constant or everyday smells, sounds and touches. We benefit from this phenomenon because our attention is focused on changes in information during stimulation and not on the elements in our environment that do not change.


Transduction is the process by which our perceptual system encodes stimulus energy as neural messages that the brain can understand. When we see, we convert light energy into these neural impulses. The energies that we perceive as visible light are only a tiny part of the broad spectrum of electromagnetic radiation. The color shade and brightness that we perceive in a light depend on its wavelength and intensity.

The Main structures of the eye: The light passes through the cornea of ​​the eye, which Cornea, a, a protective layer that breaks the light beam. Through the iris, a muscle ring, will be the size of the pupil through which the light enters the eye. The lens changed shape to reflect the rays of light on the retina to focus, the inner surface of the eye, on which the light energy is converted into nerve impulses. After coding in the retina, these are transmitted via the Optic nerve into the brain. Although the retina receives an image that is upside down, the brain processes the incoming impulses so that the image appears to be right again. Changes in the shape of the eyeball can have an impact on visual acuity.

The two types of receptors in the retina are that rod and the Cones. They differ in terms of shape, number, function, location and connections to the brain. When light enters the eye, it triggers a photochemical reaction in the rods and cones, which in turn the bipolar cells activated. Activate the bipolar cells Ganglion cells, and your Axons (which together form the optic nerve) transmit (via the thalamus) information to the visual cortex in the occipital region of the brain. The rods, which are more numerous, are mainly in the periphery of the retina and are more sensitive to light. Several rods work together to send messages to a bipolar cell, and this accumulation of information allows us to see rough images in poor lighting. The cones are in the area of ​​the Fovea focused and sensitive to color and details. A cone can be directly connected to a single bipolar cell, and this direct connection to the brain receives the finest details in the cone 's message.

Perceptions arise from the interaction between many systems of neurons, each performing a simple task. The processing begins in the multiple neuronal layers of the retina, then the 6 million cones and the 120 million rods of the retina transmit their information to the ganglion cells via the bipolar cells. The impulses travel along the axons of the ganglion cells that make up the optic nerve, to the thalamus and on to the visual cortex. In the Visual cortex (visual cortex) react Feature detectors on the special characteristics of a visual stimulus. The superordinate cells of a higher level bring this collected data together in order to then process it in other areas of the cortex. If the sensory signals The different processing levels go through, they are influenced by our assumptions, interests and expectations.

Parallel processing is the natural method of information processing in the brain; with their help one can address many aspects of a problem at the same time. The brain's ability to perform multiple tasks at the same time enables it to Sub-dimensions of vision (Color, movement, depth and shape) to different neural teams to distribute that work separately and at the same time. Other neural teams work together to bring the results together, compare them with stored information, and enable perceptions.

The theory of Young and Helmholtz: In the Tri-color theory (trichromatic theory) by Young and Helmholtz It is believed that there are three types of color receptors in the retina. Today's research found three types of cones, each of which is most sensitive to one of the 3 primary colors of light (red, green or blue). In Hering's opposite color theory two additional color processes (red versus green and blue versus yellow) and a third black-versus-white process were assumed. Modern research has confirmed that on the way to the brain, neurons in the retina and thalamus encode the color-related information from the cones in pairs of opposite colors, as is also confirmed by the phenomenon of afterimages. These two theories and the research that supports them show that the Color processing in two stages he follows.

Color constancy is our ability to perceive a consistent color in objects even though the lighting and the wavelengths change. This phenomenon shows that the brain constructs our color perception by comparing it with other objects in the environment.


Sound waves are annular bands of compressing and expanding air. Our ears take this Changes in air pressure true and convert them into neural impulses that the brain decodes as sounds. Sound waves differ in their Frequency and amplitudethat we perceive as differences in pitch and volume.

The three areas of the ear and the series of events that cause electrical impulses to be sent to the brain: The outer ear is the visible part of the ear. The Middle ear is the chamber between the eardrum and the cochlea. The Inner ear consists of the cochlea, the semicircular canals and the sacculi of the vestibular apparatus. With the help of a mechanical chain reaction, the sound waves are transmitted through the Ear canal headed and call at the end minor Vibrations of the eardrum emerged. The Bones of the middle ear amplify the vibrations and transfer them to the liquid-filled one Kochlea. Because the Basilar membrane is set in wave-like movements, which are caused by pressure changes in the cochlear fluid, the tiny hair cells are moved, which in turn trigger nerve impulses that are sent (via the thalamus) to the auditory cortex sent in the brain.

In the Spatial theory it is assumed that our brain interprets a certain pitch by decoding the position of the point (hence "spatial theory") at which a sound wave stimulated the basilar membrane of the cochlea. In the Frequency theory It is assumed that the brain decodes the number and frequency (hence "frequency theory") of the pulses that travel to the brain in the auditory nerve. Research has confirmed both theories, but for different listening areas. Position theory does not explain how we can hear low notes (which cannot be located on the basilar membrane), but it does provide an explanation for how we perceive high notes. Frequency theory does not explain how we hear high tones (individual neurons cannot fire fast enough to produce the necessary number of voltage peaks. However, frequency theory provides an explanation of how we perceive low tones. A combination of both theories explains how we hear mid-range sounds.

Sound waves hit one ear earlier and more intensely than the other. Using parallel processing, the brain analyzes tiny differences in the sounds picked up by the two ears and calculates the source of the sound.

The two types of hearing loss: Conductive hearing loss is a consequence of damage to the mechanical system that transmits the sound waves to the cochlea. Sensorineural hearing loss (or nerve hearing loss) is the result of damage to hair cells in the cochlea or to nerves connected to it. These problems can be caused by illness and accidents, but age-related disorders and constant exposure to loud noises are the more common causes of hearing loss, especially nerve hearing loss.

Cochlear implants are connected to the auditory nerve in different places; this enables them to transmit electrical impulses to the brain. These devices can help deaf children hear some sounds and learn to use the spoken language. But cochlear implants are most effective when children are very young; this means that parents have to make the decision about their deaf children. Deaf culture advocates believe the operation is unnecessary because they do not see deafness as a disability - deaf people already have a complete language: the Sign language. Some also believe that the sensory compensationthat makes other senses more sensitive, gives deaf people advantages over hearing.

Other important senses

The sense of touch actually consists of 4 different senses: the Sense of pressure, the Sense of warmth and cold and the Sense of painthat in combination produce other sensations, such as "hot". Of these, only the pressure sense has specialized receptors.

The Biopsychosocial Approach to Pain Theory: One Pain theory assumes that there is a kind of "gate" in the spinal cord that is either open to allow pain signals to rise to the brain via thin nerve fibers, or is closed to prevent them from going through. Of the biopsychosocial perspective From a person's pain experience is seen as the sum of three groups of experiences: biological influences (such as nerve fibers that send messages to the brain), psychological influences (such as the situation or our previous experiences) and socio-cultural influences (such as cultural expectations and the presence of observers). In pain control treatment, psychological and physiological elements are often used in combination.

The Sense of taste, a chemical sense, is actually exposed 5 basic sensations together (sweet, angry, salty, bitter and »Umami«) as well as from the flavors that interact with the information of the taste buds. The Taste buds on the top and back of the tongue as well as on the roof of the mouth contain the Taste receptor cells. These cells send information to an area in the temporal lobe near the area in which olfactory information be included. The influence of smell on our sense of taste is an example of sensory interaction, the ability of one sense to influence another.

This is like the sense of taste Sense of smell a chemical sensation; but there are no basic elements for the sensation of smell, as there are basic elements for the sense of touch and taste. In contrast to the receptor cells of the retina, which recognize colors by breaking them down into their components, the more than 5 million Olfactory receptor cells individual odor molecules with around 350 different receptor proteins. The receptor cells send messages to Olfactory brain, then on to the temporal lobes and parts of the limbic system. Some smells address a combination of receptors. The ability of the sense of smell spontaneous memories and arousing feelings is due in part to the close connection between the areas of the brain that process smells and those involved in memory storage.

difference between Kinaesthesia and the Sense of balance: With the help of millions of sensors for position and movement, which are distributed over the whole body, our monitors kinesthetic sense the position and movement of individual body parts. Our sense of balance is based on the Semicircular canals and the Sacculi in the vestibular apparatus the inner ear, which perceive the position and movements of our head - and thus our entire body; this is how we manage to keep the balance.

How We Perceive the World: Some Basic Principles

The interplay of attention and perception: In a process that is conventionally known as sensation, the sense of sight, hearing, taste, smell and touch sense a physical energy in the environment and encode it in form neural signals. With the help of knowledge and expectations, our brain perceives meaning in these signals. We selectively focus our attention on a limited amount of data and process it as it hits our sense organs; we ignore others. The concentrated attention blindness can result from inattentiveness or blindness to change or even blindness to choice.

Perceptual illusions

Psychologists are fascinated by perceptual illusions because they show how we normally organize and interpret sensations. When visual and other sensory information contradict each other, our brain usually resolves the mismatch by accepting the visual data, a tendency that is called visual dominance referred to as. If the sense of hearing and touch are opposed to one another, the sense of hearing probably dominates.

Perception organization

Gestalt psychologists are looking for rules that help the brain organize fragments of sensory data into shapes or meaningful forms. These researchers emphasized the old tenet that the whole is greater than the sum of its parts.In doing so, they showed that we are constantly filtering out sensory information and inferring perceptions from this in such a way that they make sense to us. The real core remains correct, even if current research shows that sensation and perception are part of a continuous information processing system, to which both Bottom-up as well as Top-down processing belong.

The Figure-ground relationship and the Principles of grouping of perceptions in the perception of shape: in order to recognize an object, we must first perceive it, i. H. see as a figure that is clearly different from its surroundings (the ground). We bring order and form into the world of stimuli by organizing the stimuli in meaningful groupings, following the rules of closeness, similarity, continuity, context and unity.

Depth perception is our ability to see objects in three dimensions, even though only two-dimensional images hit our retina. Without the depth perception we would not be able to judge the distance, the height and the depth. The Research onvisual cliff has shown in 6-14 month old toddlers that depth perception is partly innate. Many types of living beings perceive the world as three-dimensional from birth or shortly thereafter.

Binocular cues are cues for depth based on information from both eyes. At the Cue stimulus of retinal disparity The brain calculates the relative distance of an object by comparing the slightly different images that hit the two retinas of the object. The greater the difference, the closer the object must be. At the Cue stimulus of convergence the brain calculates how much our eyes are neuromuscularly tense when they move inward to look at a nearby object. The greater the tension (or the angle of convergence), the closer the object.

Monocular cues allow us to judge depth using information conveyed by only one eye. Binocular cues, on the other hand, require information from both eyes. The monocular cues include:

  • relative size (something smaller is further away),
  • Interposition (if one object blocks our view of another, it is closer than the other object),
  • Relative clarity (an object in the fog is further away than an object that can be clearly seen),
  • Texture gradient (if the texture changes, coarse, clearly structured objects are close, fine, indistinguishable objects further away),
  • Relative height (Objects that are further up in the field of view are further away),
  • Relative motion or parallax of motion (when you move, objects that are actually immobile seem to move too),
  • Central perspective (the more two parallel lines converge, the further away they are),
  • Light and shadow (closer objects reflect more light than objects further away)

Movement perception: When objects move across or towards our retina, we make the basic assumption that shrinking objects move away from us and larger objects move closer to us. But we cannot always rely on our perception of movement. Possibly, with the help of our peripheral vision, we are wrongly calculating the speed of movement of large objects. If the images hit the retina in rapid succession, this can be a Motion illusion as with the stroboscopic movement (triggered by a rapid sequence of slightly varying images) or at Phi phenomenon (triggered by quickly switching two stationary light sources on and off).

When seeing is that Constancy of perception A prerequisite for recognizing an object regardless of the change in viewing angle, distance or lighting. Because of this ability, we perceive objects as having unchanging characteristics despite the changing images they project onto the retina.

In the Constancy of shape it is our ability to perceive familiar objects (such as an opening door) as being invariable in shape. Size constancy means to perceive objects as unchangeable in their size in spite of their changing images on our retina. There is a close relationship between perceived size and perceived distance. Knowing the size of an object is an indication of its distance; knowing its distance is an indication of its size. This interplay sometimes leads us astray, for example when we misinterpret monocular cues for distance and come to wrong conclusions, as with the Moon illusion, the Ponzo deception and the Müller-Lyer deception.

In the Brightness constancy it is our ability to perceive an object as having a constant brightness even when the lighting - the light that is thrown on it - changes. The Color constancy allows us to perceive the color of an object as unchangeable, even when the lighting changes. In both cases, the brain perceives the property (brightness or color) as being relative to the objects in the environment.

Perception Interpretation

Research on the restoration of vision and sensory deprivation contribute to our understanding of how the nature and environment interact in our perception: If all aspects of visual perception were completely present from birth, people who were born blind would have to could see again after an operation, actually have normal visual perception. That's not the case. After surgical removal of the cataract z. For example, adults who were blind from birth can distinguish between figure and ground and perceive colors, but they lack the experience to recognize shapes, forms and whole faces. There are further findings for animals that grew up with severely restricted visual input and that developed permanent visual impairment when they were exposed to normal visual stimuli again. Clinical and experimental evidence suggests that there is a critical phase for some aspects of sensory and perception development. Without the stimulation of early visual experiences, the brain's neural organization will not develop normally.

Do people put on glasses that shift the world slightly to the left or right or even turn it completely upside down (Reversible glasses), they are initially disoriented, but they soon manage to adapt to the new context and, with a little practice, move easily. This research demonstrates our ability to adapt to an artificially altered field of vision and to coordinate our movements in response to this new world.

A Perception set is a mental predisposition that functions as a lens through which we see the world. Once again, the system and the environment interact: the sensory signals bounce off our experiences, learned assumptions and beliefs. Because ours learned terms (schemes) as Pre-stimulus (prime) serve to organize and interpret ambiguous stimuli in a certain way, our perception expresses our version of reality. That is why some of us "see" monsters, faces and UFOs or "hear" messages and others do not.

When we perceive a particular stimulus that we could interpret using several different schemes, we scour the immediate context for information. Context creates expectations that guide our perceptions. An emotionally toned context can influence our interpretation of other people's behavior (and our own behavior). Perception set and Context effects enter into an interaction and help us construct our perceptions.

Industrial psychologists encourage developers and designers to consider people's perceptual abilities, bypassing the curse of knowledge and planning the test on a living object in order to uncover problems that can be traced back to perception before the finished products are produced and sold. Psychologists who deal with the human factor have made air travel and space travel safer, better designed devices, equipment and work environments, and hearing aids that are easier to use.

Does extrasensory perception really exist?

Extra-sensory perception is a form of alleged paranormal phenomena (another form is psychokinesis). The 3 bestverifiable forms of extra-sensory perception

  • the telepathy (Communication from one soul to another),
  • Clairvoyance (Perception of spatially distant events) and
  • precognition (Perception of future events).

The skepticism of most university psychologists focuses on 2 main points, with the last being the more important:

  • To believe in extrasensory perception, one has to believe that the brain can perceive without receiving sensory signals.
  • Parapsychologists have so far not been able to replicate (reproduce) the phenomena of extra-sensory perception under controlled conditions.