S & P Chapter 1

• Sensation: First contact between organism and environment

• Perception: Our conscious experience of objects and objects relationship

  • Some people treat these as distinct processes, but others blur the lines

• Perceptual World: the observer’s experiences of the surrounding physical world

  • experiences may or may not be closely related to the physical world itself

• Different perspectives of perception

  • Physiological: neural processing, transduction

  • Psychophysical: relationship between physical world and psychological world

  • Cognitive: how perception is affected by prior knowledge

  • Ethological: how animal/human senses have been used for survival

• The Perceptual Process

  • Distal Stimulus: stimulus out in the environment

  • Proximal Stimulus: stimulus activating our receptors

  • Transduction: changing of one energy form to another

  • Neural Processing: signal gets processed through networks of neurons

  • Perception: the image is “seen”

  • Recognition: the object/image is recognized by the perceiver

  • Action: how do I respond

  • This is a dynamic process. That is, constantly changing

• Goldstein’s Model of Perception

• Knowledge

  • Top-down Processing: the effect prior knowledge has on the perceptual process. Include memories, expectations, and factual knowledge. With knowledge

  • Bottoms-up Processing: processing from the sensory impact to transduction and constructing the perception from the stimulus. Without knowledge

• Studying Perception

  • Psychophysical Method

    • connect stimulus to perception, the behavior is perception

    • describe the relationship between the psychological experience and the physical world

  • Physiological Method

    • measuring neurophysiological processes

    • neurons and electrical signals

    • brain structure

  • Combination of Psychophysical and Physiological Methods

• Measuring Perception

  • Description

    • Phenomenological approach: ask people to describe what they’re perceiving, basic properties

  • Recognition

    • Ask people to tell you what they are perceiving. What is it?

  • Detection

    • Absolute Threshold: minimum energy needed to detect

    • Difference Threshold: minimum difference needed to detect

  • Magnitude Estimation

    • Response Compression: Brightness

    • Response Expansion: Pain

  • Search

• How to measure thresholds

  • Method of limits:

    • ascending and descending series of stimuli

    • average turnaround points

    • habitual response issue: respond to the same

    • anticipation issue: anticipate when change will occur, can be inaccurate

  • Method of adjustment:

    • observer freely adjusts stimuli

    • habituation can happen: develop a habit of responding

    • anticipation: think match is near

    • used for quick threshold estimates and color matching studies

  • Method of constant stimuli:

    • set series of stimuli

    • present to observer multiple times

    • threshold lies in the range

    • produce a psychometric function

    • takes a long time

  • Signal Detection Theory: gets rid of threshold

HOMEWORK DUE 2/3

1 & 2) Done in class

3) Difference Threshold, Method of limits, I would blindfold participants and put a certain number of pennies and decrease the number until the person notices.  

4) Absolute threshold, Method of constant stimuli, I would create an online quiz and have the participants compare two random pitches to identify the higher or lower pitch between two sounds.

5) Difference Threshold, Method of adjustment, I would put the paper with the small dot a certain far distance and have the participants increase the distance by 6-inch intervals until they can see the small dot.  

• Staircase procedure for threshold

  • reach threshold faster

  • efficient: not above or below threshold very often

  • many variants: this is 1 up/2 down

  • threshold is average of reversal points

• Psychometric Function

  • create an ‘S’ curve from data

  • threshold is 50% seen point as shown in absolute threshold measures

  • interval of uncertainty is between 25% seen and 75% seen

  • for Difference Thresholds, the graph can be used to calculate the JND

  • JND = Just Noticeable Difference

• JND and Weber Fraction

  • JND is delta I - the threshold for detecting a difference between two stimuli

  • If intensity is 100gm and delta I is 10 the Weber fraction is .10

  • Then if the intensity is 200gm the delta 1 would be 20 if the Weber fraction is .10

  • Weber’s Law states the difference threshold is proportional to the stimulus intensity

  • Weber’s Law applies to many sensory modalities

Changes in Psychometric Function

• Basic Brain Structure

  • Cerebral Cortex: outer 2mm of brain

  • Modular structure: different areas perform different tasks

• Lobes of the Brain and the Senses

  • Occipital Lobe - primary visual cortex

  • Parietal Lobe - skin senses, touch, temperature, pain

  • Frontal Lobe - Receives info from all senses

  • Temporal Lobe - primary auditory cortex

• Use microelectrodes inserted into cell - reference (outside) recording (inside)

• Action Potentials

  • Propagated - once triggered, continues same all the way

  • Refractory Period - time between firings when neuron can’t fire (1 ms)

  • Spontaneous Activity - action potentials that occur in the absence of stimuli

    • activity can increase (excitatory) or decrease (inhibitory)

  • Leads to synaptic transmission

• Synaptic events

  • Neurotransmitters - chemicals stored in presynaptic vesicles

  • Receptor sites - sites where neurotransmitters bind, vary in shape

  • Excitatory neurotransmitters - depolarize postsynaptic cell

  • Inhibitory neurotransmitter - hyperpolarize postsynaptic cell

• Neural Circuitry

  • No convergence - linear, firing rate remains constant

  • Convergence - many cells transmit into one, firing rate increases

  • Convergence - plus inhibition - some cells decrease firing rate

  • Divergence - one cell transmits to many, info goes to many areas

• Receptive fields - the area the receptors that influences the response of the neuron

• Firing Rates - opponent cells, 1st line - spontaneous, 2nd line - response, 3rd line - response, 4th line - response

  • responses vary for the two cells

  • they are opposite except for the spontaneous firing rate