Notes

Ch. 1) Introduction to Perception

• Sensation

  • “Elementary” process that occurs at the beginning of the sensory system

• Perception

  • complex processes that involve higher-order mechanisms such as interpretation & memory that involve activity in the brain

• Stimulus

  • a thing that evokes a specific functional organ/tissue

• Environmental

  • all objects in available to the observer

• Distal

  • in the distance

• Proximal

  • in proximity

• Principal of Transformation

  • stimuli & responses created by stimuli are transformed/changed between the environmental stimuli & perception

• Principal of Representation

  • one’s perception is based not on direct contact with stimuli but on representations of stimuli, which are constituted by activity in the person’s nervous system

• Steps 1 & 2

  • Stimuli

    • Environmental stimulus

    • Observer selectivity attends to objects

    • Stimulus impinges on receptors resulting in internal representations

  • Observer selectively attends to objects

  • Impinges on receptors resulting in internal representation

  • Principal of Transformation

    • Occurs throughout the perceptual process

      • cornea

      • lens

      • retina (transduction)

      • midbrain

      • cortex

        

  • Principal of Representation

• Step 3

  • Receptor processes/Transduction

  • Sensory receptors

    • cells specialized to respond to environmental energy, with each sensory system receptor specialized to respond to a specific type of energy

  • Visual

    • respond to light

  • Auditory

    • respond to pressure changes in the air

  • Touch

    • respond to pressure transmitted through the skin

  • Smell

    • respond to chemicals coming through the nose

  • Taste

    • respond to chemicals coming through the mouth

  • Visual pigments

    • light-sensitive chemicals

    • shape perception in

      • the ability to see dim light depends on having a high concentration of light-sensitive pigment in the receptors

    • there are different types of pigments which respond best to light in different parts of the visible spectrum

  • Transduction

    • the transformation of one form of energy to another form

  • Visual receptors transform light energy into electrical energy because they contain visual pigment

  • Transduction by the visual pigment is crucial for perception

    • without it, information about the representation of the environmental stimuli formed on the retina wouldn’t reach the brain & perception wouldn’t occur

• Step 4

  • Neural processing

    • changes that occur as signals are transmitted through the maze of neurons

  • Primary receiving areas

    • Topographic representation

      • Occipital lobe

        • vision

      • temporal lobe

        • auditory

      • parietal lobe

        • somatosensory

      • frontal lobe

        • smell & taste

• Steps 5-7

  • Behavioral responses

  • Experiences & action

    • perception

      • occurs as a conscious experience

    • recognition

      • occurs when an object is placed in a category giving it meaning

    • action

      • occurs when the perceiver initiates motor activity in response to recognition

    • expectations affect what we see

• Knowledge

  • any information the perviever brings to a situation

  • Bottom-up processing

    • aka: data-based processing

    • based on incoming stimuli from the enviornment

    • you’re building the perception from the ground up

  • Top-down processing

    • aka: knowledge-based processing

    • based on perciever’s pervious knowledge

      • cognitive factors

  • Percpetion is determined by an interaction between bottom-up processing and top-down processing

• Oblique Effect

  • the phenomenon where we are significantly better at perceiving & discriminating the orientation of lines/edges that are vertically/horizontally aligned compared to oblique angles (tilt of diagonal lines)

• Measuring perception

  • Absolute threshold

    • smellest amount of energy needed to detect a stimulus

    • Method of limits

      • stimuli of different intensitites present in ascending & descending order

      • Observer responds to whether they percieved the stimulus

      • Cross-over point is the threshold

        • Average those to points to get the overall threshold

• 5 Questions about the perceptual world

1. What is the perceptual magnitude of a stimulus?

   1. magnitude estimation

2. What is the identity of the stimulus?

   1. recognition testing

3. How can I quickly react to it?

   1. reaction time

4. How can I describe what is is out there?

   1. phenomenological report

5. How can I interact with it?

   1. physical tasks & judgment

Appendix A

• Method of adjustment

  • stimulus intensity is adjusted continuously until the observer detects it

    • repeated trials averaged for threshold

• Absolute threshold

  • method of constant stimuli

    • 5-9 stimuli of difference instensities are presented in random order

    • Multiple trials

    • threshold is the inensity that results in detection in 50% of trials

Appendix B

• Difference threshold/DL

  • DL

    • difference limen

  • smallest difference between 2 stimuli a person can detect

  • same methods can be used as for absolute threshold

  • as magnitude of stimuli increases, so does DL

  • Weber’s Law explains that difference

    • DL/S=K

      • S - standard

      • K - constant

Appendix C

• Estimating Mangitude

  • scaling

  • stimuli are above threshold

  • observer is given a standard stimulus & a value for it’s intensity

  • observer ccompares the standard stimulus to test stimulu by assigning number relative to the standard

  • response expansion

    • the perceived magnitude increases more quickly than the intensity

  • response compression

    • the perceived magnitude increased more slowly than the intensity

  • Steven’s Power law

    • P=KSn

    • realtionship between intensity & perception magnitude is a power function

Appendix D

• Threshold measurements can be influenced by how a person chooses to respond

  • liberal responder

    • responds “yes” if there is the slightest possibility of experiencing the stimulus

  • conservative responder

  • cerierion

    • a person’s individual response bias

  • signal detection theory

    • used to take individuals response criterion into accound

• Low threshold = high sensitivity

• High threshold = low sensitivity

Ch. 2) The Beginnings of Perception

Ch. 3) Neural Processing

Ch. 4) Cortical Organization

Ch. 5) Perceiving Objects & Scenes

• Why is it so difficult to design a perceiving machine?

  • the stimulus on the receptors are ambiguous

    • inverse projection problem

      • an image on the retina can be caused by an infinite number of objects

    • objects can be hidden/blurred

      • occlusions are common in the enviornment

Review

Ch. 1

• The steps in the perceptual process (Fig 1.1 pg 5)

  • Stimulus: steps 1 & 2

    • environmental stimulus,

      • Stimuli from the environment

        • Distal

          • Stimuli in the distance

        • Proximal

          • Stimuli on the retina

    • principle of transformation,

      • stimuli & responses created by stimuli are transformed/changed between the environmental stimuli & perception

    • principle of representation,

      • one’s perception is based not on direct contact w/ stimuli but on representations of stimuli that are constituted by activity in the person’s nervous system

    • and attended, stimulus on receptors

  • Receptor Processes/Transduction: step 3

    • transduction

      • the transformation of one form of energy to another

      • visual pigments

        • light-sensitive chemical

      • transduction by the visual pigment is crucial for perception

        • the ability to see dim light depends on having a high concentration of light-sensitive pigment in the receptors

        • there are different types of pigments, which respond best to light in different parts of the visual spectrum

  • Neural Processing: step 4

    • changes that occur as signals are transmitted through the maze of neurons

    • transmission, processing)

  • Behavioral Responses: steps 5-7

    • perception

      • occurs as a conscious experience

    • recognition,

      • occurs when an object is placed in a category giving it meaning

    • action

      • occurs when the perceiver initiates motor activity in response to recognition

  • Knowledge

    • any information the receiver brings to a situation

    • top-down processing,

      • based on the perceiver’s previous knowledge

    • bottom-up processing,

      • based on incoming stimuli from the environment

    • priming (e.g. the rat-man)

• Approaches to Studying Perception (Fig 1.9) [oblique effect examples]

  • Psychophysical: the stimulus-perception relationship

  • Physiological the stimulus-physiology relationship the physiology-perception relationship

• Measuring Perception

  • Absolute threshold

  • Measuring thresholds

    • Method of limits, method of constant stimuli, method of adjustment (Appendix A, B) How each finds the threshold

  • Magnitude Estimation

• Response compression, Response expansion, Stevens’s Power Law (Appendix C)

  • Signal Detection: Response Criterion (liberal vs conservative) (Appendix D)