Modules 16-21: Sensation and Perception Module 16: Sensation

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Modules 16-21: Sensation and Perception
Module 16:

  • Sensation- the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment (physical)

  • Perception- the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events (psychological)

  • Bottom-up processing- analysis that begins with sensory receptors and works up to the brain’s integration of sensory information (data-driven)

  • Top-down processing- information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations (conceptually-driven)

  • Likelihood principle- we will perceive the object that is most likely to be the cause of our sensory stimulation

  • Selective Attention- the focusing of conscious awareness on a particular stimulus

  • Cocktail party effect: one’s ability to attend to only one voice among many

  • Flow: so caught up in an experience that we miss out on a particular stimulus

  • Inattentional blindness- failing to see visible objects when our attention is directed elsewhere

  • Change blindness- failing to notice changes in our environment

  • Choice blindness: when the object of one;s preference is switched, they don’t acknowledge the difference and tend to find explanations for this altered choice

  • Transduction- conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brain can interpret

  • Our senses

  1. Receive sensory stimulation often using specialized receptor cells)

  2. Transform it into neural impulses

  3. Deliver neural information to the brain

  • Psychophysics- the study of relationship between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them

  • Absolute threshold- the minimum stimulation needed to detect a particular stimulus 50% of the time

  • Signal detection theory- a theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes that there is no single absolute value threshold and that detection depends partly on a person’s experience, expectation, motivation, and alertness

  • Subliminal- below one’s absolute threshold for conscious awareness

  • Priming- the activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response

  • Difference thresholds or just noticeable differences (jnd)- the minimum difference between two stimuli required for detection 50% of the time

  • Weber’s Law- the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount)

  • Sensory adaptation- diminished sensitivity as a consequence of constant stimulation

    • ex) nasty smells, hot showers

    • Focuses our attention on informative changes in our environment

  • Habituation- your brain stops paying attention to things that don’t change. However, as soon as that thing changes, it recaptures your attention

    • ex) noise, billboards

Module 17:

  • Perceptual Set- a set of mental tendencies and assumptions that greatly affects (top-down) what we perceive.

  • Extrasensory Perception (ESP): the controversial claim that perception can occur apart from sensory input; includes:

    • Telepathy- mind-to-mind communication

    • Clairvoyance- perceiving remote events, such as a house fire in another state.

    • Precognition- Perceiving future events, such as an unexpected death in the next month.

    • Psychokinesis- “mind over matter”- Ex. Levitating a table or influencing the role of a die.

  • Parapsychology- the study of paranormal phenomena, including ESP and psychokinesis.

Module 18:

  • Our eyes receive light energy and transfer it into neural messages that our brain then processes it to what we see.

  • The Stimulus Input: Light Energy

  • Wavelength- the distance from the peak of one light or sound wave to the peak of the next.

  • The wavelength determines the hue- the dimension of color that is determined by the wavelength of light; we know as the color names.

  • Intensity- the amount of energy in a light or sound wave, which we perceive as brightness or loudness, determined by the wave’s amplitude.

  • The Eye

  • Light enters the eye through the cornea, which protects the eye and bends light to provide focus.

  • Then goes through the pupil- the adjustable opening in the center of the eye through which light enters.

  • Iris- a ring of muscle tissue that forms the colored portion and controls the size of the pupil.

  • Lens- a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening.

  • Retina- the light-sensitive inner surface of the eye, containing the receptor rods and cones plus neurons that begin the processing of visual information.

  • Accommodation- process by which the eye’s lens changes shape to focus near or far objects on the retina.

  • The Retina

  • Rod- retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don’t respond.

  • Cones- receptor cells that are concentrated near the center of the retina and function in daylight or well-lit conditions. They detect fine detail and give rise to color sensation.

  • This activates the bipolar cells, that activates the ganglion cells, whose axons twine together like the strands of rope to form the optic nerve- carries neural impulses from the eye to the brain.

  • Blind spot- the point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there.

  • Cones cluster around the fovea- the central focal point in the retina, around which the eye’s cone cluster.

  • Cones to detail and color, & rods to faint light and send combined messages.

  • Visual Info Processing

  • Information from the retina’s neural layers goes to the visual cortex.

  • Feature Detection

  • David Hubel & Torsten Wiesel worked on feature detectors- nerve cells in the brain that respond to specific features of the stimulus.

  • When disrupted we can’t interpret faces.

  • Parallel Processing

  • Parallel processing- the processing of aspects of a problem simultaneously; the brain’s natural mode of information processing, step-by-step (serial) processing of conscious problem solving.

  • Color Vision

  • Our threshold is low therefore it is easy to detect many colors.

  • Young-Helmholtz trichromatic theory- the retina contains three different color receptors-- one most sensitive to red, one to green, one to blue-- which, when stimulated in combination, can produce the perception of any color.

  • Opponent-process theory- the theory that opposing retinal processes enable color vision. For example, some cells are stimulated by green and inhibited by red.

Module 19:

Visual Organization

  • Gestalt - meaning a “whole” (Ex: Necker Cube)

  • In perception, the whole may exceed the sum of its parts

Form Perception

  • Figure and ground - perceiving an object (the figure) as distinct from its surrounding (the ground)

  • Grouping - organizing stimuli into coherent groups

    • 3 examples: Proximity, Continuity, and Closure

Depth Perception

  • Depth perception allows us to judge distance

  • This depth perception was tested in infants through the visual cliff experiment

  • Binocular cues - judge the distance of nearby objects w/ the use of 2 eyes

    • The greater the retinal disparity between 2 objects, the closer the object

  • Monocular Cues - depth cues available to each eye separately

    • Examples: relative size, interposition, relative height, texture gradient, aerial perspective, relative motion, linear perspective, and light & shadow

Motion Perception

  • Phi Phenomenon - illusion of movement created when 2 or more adjacent lights blink on and off in quick succession (Ex: Christmas Lights)

Perceptual Constancy

  • Perceptual constancy - perceive objects as unchanging even as retinal images change

  • Color Constancy - perception of consistent color even when illumination varies

  • Shape Constancy - perceive objects as constant even while our retinas receive changing items of them (Ex:Way you view a door)

  • Size Constancy - perceive objects as having a constant size, even while our distance from them varies (Ex: Our distance from a car)

    • Moon Illusion

  • Context is important

Experience and Visual Perception

  • Experience guides our perceptual interpretations

  • People blind from birth who gained sight after surgery lack the experience to visually recognize shapes, forms, and complete faces

  • There is a critical period for some aspects of sensory and perceptual development

  • Our perceptual adaptation to changed visual input makes the world seem normal again

Module 20:


Audition- the sense or act of hearing.

Frequency- the number of given wavelengths at any given time.

Pitch- a tone experienced in highness or lowness.

Cochlea- a coiled bony, fluid filled tube in the inner ear; sound waves traveling through the cochlear fluid trigger nerve impulses.

Sensorineural hearing loss- hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerves, also called nerve deafness.

Conduction hearing loss- hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea.

Cochlear implant- a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea.

Place Theory- the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated.

Frequency Theory- the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch.
Key concepts:

Amplitude determines loudness

Frequency determines pitch,ex: low frequency low pitch.

Long waves have low frequency, ex: short waves have high frequency.

Sounds are measured in decibels.

How sound is turned into neural impulses

Outer ear -> auditory canal -> eardrum -> middle ear ( three bones, hammer anvil and stirrup) -> inner ear -> Cochlea -> basilar membrane -> hair cells lining the surface. These hair cells trigger impulses on adjacent nerve cells which form the auditory nerve and send signals to the auditory cortex.

Simple version is vibrating air to fluid waves to electrical impulses to the brain.

Prolonged exposure to anything above 85 decibels produces hearing loss.

Brain interprets loudness on the number of activated hair cells.

Having two ears allows us to locate sounds due to the delay and difference of intensity between ears.

Herman von Helmholtz is associated with place theory.

Georg von Bekesy cut open cochleas of guinea pigs and cadavers.

Module 21:

  • Skin sensations are variations of the basic four (pressure, warmth, cold, and pain.

  • Nociceptors- sensory receptors that detect harmful temperatures, pressure, or chemicals.

  • Ronald Melzack and Patrick Wall’s:

    • Gate-Control Theory- the theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain. The “gate” is opened by the activity of pain signals traveling up small nerve fibers and is closed by activity in larger fibers or by information coming from the brain.

  • Psychological Influences:

    • Athletes can play through pain.

  • Socio-Cultural Influences:

    • When others are feeling pain, we tend to feel more pain.

  • Anosmia- people who are unable to smell.

  • Kinesthesia- the system for sensing the position and movement of individual body parts.

  • Vestibular Sense- the sense of body movement and position, including the sense of balance. Monitors your head’s (thus your body’s) position and movement.

  • Sensory Interaction- the principle that one sense may influence another, as when the smell of food influences its taste.

  • McGurk Effect- seeing mouth movements for “ga” while hearing “ba” we may perceive “da”.

  • Embodied Cognition- in the psychological science, the influence of bodily sensations, gestures, and other states on cognitive preferences and judgements.

  • Synesthesia- where one sort of sensation (such as hearing sound) produces another (such as seeing color).

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