Sensation and Perception


In psychology, sensation and perception represents our method of interpreting our world through stimuli. This includes the five major senses of vision, hearing, touch, taste, and smell, as well as, the kinesthetic and vestibular senses.

I. Sensing and Perceiving the World


The Processes and Purposes of Sensation and Perception

In the specific study of sensation and perception, there are three main research groups:
  1. Ophthalmology: study of the eye's structure, function, and diseases.
  2. Audiology: science concerned with hearing.
  3. Neurology: scientific study of the nervous system.

Understanding sensation and perception requires one to comprehend the physical properties of our perception - light, sound, texture, etc. The physical environment is represented according to the perceiver, and therefore relative only to the perceiver. The global purpose of sensation and perception is survival, and this includes adapting to new environments and detecting prey, predator, or potential mates in order to survive as a species.
  1. Sensation: the process of receiving stimulus energies from the external environment and transforming those energies into neural energy (records information about the physical environment: light, heat, smell, etc).
  2. Perception: the process of organizing and interpreting sensory information so that it has meaning (interprets the pattern of information, such as light, and gives it meaning).
  3. Bottom-up processing: when sensory receptors register information about the external environment and send it up to the brain for interpretation (attempts to make sense of new information).
  4. Top-down processing: starts with cognitive processing in the brain (uses information already known and applies it to the new information).
  5. Sensory Receptors: specialized cells that detect stimulus information and transmit it to sensory nerves and the brain.

Threshold and Sensory Adaptation

When dealing with multitudes of stimulus energies, the sensory systems must detect varying degrees of these stimuli. There is a minimum requirement of a stimuli in order for a sensor to detect it. Also, the sensory systems will adapt according to the environments variations of stimuli.
  1. Absolute Threshold: the minimum amount of stimulus energy that a person can detect.
  2. Difference Threshold: simply the noticeable difference between two stimuli.
  3. Sensory Adaptation: a change in responsiveness of the sensory system based on the average level of surrounding stimulation.

II. The Visual Stimulus and the Eye


Light and the Structure of the Eye

The stimulus for vision is light, and the basic form of white light (electromagnetic energy) is described in terms of wavelengths. The wavelengths of light that reflect from the stimulus determine its color. The structure of the eye manipulates the wavelengths in order to perceive light.
Brain-Optic-Nerve.jpg
The path of the optic nerve to the occipital lobe.
Labeled_Eye.jpg
1.Cornea, 2.Pupil, 3.Iris, 4.Lens, 5.Retina, 6.Fovea, 7a.Blind Spot, 7b.Optic Nerve

  1. Cornea: a clear membrane in front of the eye.
  2. Pupil: the opening center of the iris that allows light to enter the eye.
  3. Iris: a circular muscle that expands and contracts in order to control the amount of light entering through the pupil.
  4. Lens: transparent and semi flexible disk-shaped, and it brings the images into focus.
  5. Retina: converts electromagnetic energy into neural impulses for processing in the brain.
  6. Fovea: central focus of the lens.
  7. Optic Nerve: carries the visual information to the brain for further processing, and where the neurons meet to form the optic nerve is the blind spot.
  8. Optic Chiasm: is where the optic nerve fibers divide, and approximately half of the nerve fibers cross over the midline of the brain.

Color Vision

There are multiple theories as to how color is processed by the retina, but the two main theories are as follows:
  • The trichromatic theory states that color perception is produced by three types of cone receptors in the retina that are particularly sensitive to different, but overlapping, ranges of wavelengths (fails to explain afterimages).
  • The opponent-process theory states that cells in the visual system respond to red-green and blue-yellow colors; a given cell might be excited by red and inhibited by green, whereas another cell might be excited by yellow and inhibited by blue (explains afterimages).

Visual Perception

Supporting vision is the perception of dimensions. The brain distinguishes distance, position, height, width, and length through simply interpretations of the environment.
  1. Closure: the brain's attempt to interpret a vague, or ambiguous, stimuli.
  2. Perceptual Organization: or figure-ground relationship, is the principle by which we organize the perceptual field into stimuli that stand out (figure) and those that are left over (background, or ground).
  3. Depth Perception: the ability to perceive objects three-dimensionally through the use of interposition (overlapping) and/or shadows.

III. Hearing


The Structure of the Ear

The major benefits of sound are communication and language. The ear simply takes sound waves and amplifies them. Pitch is the perceptual interpretation of frequency of sounds.
Ear-Structure.jpg
  • Outer Ear
    1. Pinna: collects sounds.
    2. Auditory Canal: channels the sounds to the ear drum.
  • Middle Ear
    1. Eardrum: vibrates in response to the sounds and amplifies them.
    2. Hammer: reverberates in collaboration with the eardrum.
    3. Anvil: reverberates in collaboration with the hammer.
    4. Stirrup: reverberates in collaboration with the anvil.
  • Inner Ear
    1. Oval Window: transmits the sounds waves from the stirrup to the cochlea.
    2. Cochlea: tubular structure coiled like a snail that converts the sounds into impulses that the brain can interpret.

IV. The Other Senses


Smell

The sense of smell is primarily a precursor to taste for humans. Other animals, such as dogs, use smell in much more appreciated way. However, smell can determine things like whether food is rotten before you taste it. The receptor cells in the olfactory epithelium are responsible for converting the chemicals into processable information in the brain.

Taste

Taste is a major source of pleasure. The stimuli for this sense is interpreted by bumps that cover your tongue called papillae. The taste buds are located on the sides of these bumps and act as the receptor cells for taste.

The Skin Senses

The largest sensory system, the skin senses, is known as the cutaneous system, or the feeling of pressure, pain, and temperature. These sensations are recognized by sensory fibers that line the underside of epidermis.
  1. Pressure: basic feeling of touch. Humans experience this sensation by the mechanical pressure against their skin.
  2. Pain: extremes of any sensation. High mechanical pressure, intense temperature, or extreme volumes of sounds can all cause pain.
  3. Temperature: monitors the temperature of the body. It uses two types of thermoreceptors that detect warm and cold. We both types are stimulated simultaneously, the "hot" sensation occurs.

The Vestibular Sense and Kinethesis

The simply motor functions of the body, such as movement, balance, and orientation, are interpreted through these senses.
  1. The Vestibular Sense: responsible for balance. The main functions of the vestibular sense occur in the semicircular canals inside the inner ear.
  2. Kinethesis: awareness of your body in space.

Extrasensory Perception

Simply stated, the sixth sense. This sense was purely created in order to explain seemingly unnatural coincidences.


1. What are three physical properties of the objects of our vision, hearing, and touch?

2. How is physical energy taken in to our neural system?

3. The lowest amount of stimulus energy detected is our: ?

4. The only sensory system that does not use the Thalamus as a pathway to the neural system,
but rather moves through the Olfactory areas in the temporal lobe is: ?

5. Any intense stimulation, such as too much light, hot food, or pressure transforms into: ?


Answer Key:
1. Light, sound, texture.
2. Specialized receptor cells.
3. Absolute Threshold.
4. Smell.
5. Pain.