Chapter 5 - Sensation and Perception

Getting Started

• Sensation (Bottom-Up Processing) - “the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment” (pg. 133)

• Perception (Top-Down Processing) - “the process by which our brain organizes and interprets sensory information, transforming it into meaningful objects and events” (pg. 133)

• Transduction - “the process of converting one form of energy into another that our brain can use” (pg. 132)

Psychophysics

• An early research area in psychology

• Psychophysics - the study of the relationship between physical stimulation and psychological experience

• Absolute Threshold - “the minimum stimulus energy needed to detect a particular stimulus” (pg. 133)

  • 50% of a group detects the stimulus

• Signal Detection - Individual absolute thresholds vary with our psychological state (expectations, motivations, and alertness)

Difference Threshold

• Difference Threshold a.k.a., just noticeable difference (jnd) - The minimum difference in stimulation that a person can detect 50% of the time

• Weber’s Law - Difference thresholds increase in proportion to the size of the stimulus

Eye - Rods and Cones

• Color-sensitive cones are concentrated around the fovea, while the color-blind rods dominate the periphery of the retina.

• Brain uses parallel processing of sensory information

Perceptual Organization

Depth Perception

• Gestalt - German for “form”; “whole”

  • “The whole may exceed the sum of its parts”

  • All the parts (what your senses give you) form a whole object in your brain

    • Just the colors of a bird can’t help you identify it (blue, green, brown could be hummingbird or peafowl), but all parts put together can help you identify the species

• Depth Perception - Visual cliff

• Need both eyes to accurately estimate depth using retinal disparity

  • Retinal disparity - objects not being in the same place when off-center in front of you and looked at by one eye, helping you more accurately perceive distance

• Two different ways to perceive depth - binocular cues and monocular cues

  • Binocular cues - use both eyes to perceive depth of objects close to us

  • Monocular cues - use one eye to perceive depth of objects far from us

Motion Detection

• Another basic aspect of vision

• Provides an adaptive advantage

• Troxler Effect - Objects in the peripheral retina disappear under conditions of steady, unmoving stimulation but are revitalized by movement in the periphery

Perceptual Constancy

• Perceptual Constancy - “Perceiving objects as unchanging… even as illumination and retinal images change” (pg. 149)

  • Vision perceiving objects shrinking as they get further away BUT knowing they are NOT actually shrinking

Hearing

• The perceived direction of a sound is related to differences in the time at which the sound is received by each ear

Touch

Mix of Four Distinct and Basic Senses:

1. Pressure

2. Warmth

3. Cold

4. Pain

Combination Examples:

Cold + Warm = Hot

Cold + Pressure = Wetness

• Touch localization - Noticing where on your body you experience touch

• Touch localization is partly dependent on distance of the body part that is touched to the brain

Body Position and Movement

• Kinesthesia - “System for sensing the position and movement of individuals body parts” (pg. 159)

• Vestibular Sense - “Sense of body movement and position, including the sense of balance” (pg. 159)

  • i.e., equilibrium

Functions of vestibular system (inner ear):

1. Maintains balance and upright posture

2. Controls eye position as we move our heads when viewing objects

• Continuous Movement

  • Currents in the semicircular canals

    • Compensatory eye movements

• Nystagmus - Reflex movement evoked by vestibular stimulation

Vision & Equilibrium

• Our ability to maintain balance depends on visual cues

• Related to a cognitive style:

1. Field Dependence - Rely on visual cues

2. Field Independence - Rely on vestibular cues

Hypnosis

Mesmer (Anton Mesmer)

Two Main Theories:

1. Social Influence Theory - Hypnosis can be explained through other psychological experiences (Putting on an act as a good subject, even subconsciously)

2. Dissociation Theory - Separating into parts of yourself (Believing when given the suggestion of something)

• Dissociation - split in consciousness that allows some thoughts and behaviors to occur simultaneously with others

  • Hidden Observer - Part of your body still knows what’s going on

• Hypnotic Susceptibility - person’s ability to become deeply hypnotized; suggestibility

What affects this:

• Ability to become immersed in a role

• Absorption - ability to become highly involved in sensory or imaginative sequences

• Positive Attitude

• Motivation - self motivated for hypnotism works best

• Expectancy - skepticism makes it less likely to work