Ch 1. Foundations Flashcards
a process by which some form of physical energy is transformed into a psychological experience
Perception
4 step process of perception
distal stimulus (phone bing)–> proximal stimulus (sound entering ears)–>pros signal converted into neural signal–>signal processing ing brain
3 things the Psychological Approach is concerned with
-behavioural response to stimuli
-perceptual abilities
-limitations of human perception
(Describes the relationship between the physical stimulus and the reaction.)
Phenomenological/Naturalistic: What? Advantage? Disagvantage?
-observe naturally occurring events
-verbal description of experiences
-Criticisms
can not study non-verbal people or animals
not all information consciously available
-Advantages
may point to new areas of study
(Blindsight?)
Psychophysical Approach:
What? Advantage? Disagvantage?
-precise control over the stimulus and the response (AKA experimental approach)
-Criticisms
very artificial
-Advantages
relationship between stimulus and experience can be precisely quantified
can make cause/effect conclusions
Psychophysics the points
Detection (low intensity stimuli)
absolute threshold
Discrimination/difference (more intense stimuli)
Difference threshold or just noticeable difference (jnd)
Scaling (more intense stimuli)
rating subjective magnitude
absolute threshold
Alternatively defined in terms of “sensitivity” which is the inverse of threshold (i.e., a low threshold indicates high sensitivity and a high threshold indicates low sensitivity)
3 methods for absolute threshold
Method of Adjustment, Method of Limits, Method of Constants
Method of Adjustment
Typically, observer has control of stimulus
Adjust intensity of stimulus until target is just detectable
Typically make adjustments from above and below
Can be used to measure both detection and discrimination
-Advantages:
Fast
Avoids boredom
-Disadvantages:
Subject bias
Possibility of adaptation
Method of Limits
Experimenter has control of stimulus Adjust intensity in discrete steps until observer reports that stimulus is just detectable Typically make adjustments from above (descending series) and below (ascending series) Can be used to measure both detection and discrimination -Advantages: Reduces observer bias Reduces adaptation Simple to calculate threshold -Disadvantages: Inefficient Errors of anticipation (“jump the gun”) Errors of habituation (“maintain response”)
Method of Constants
Experimenter has control of stimulus
Several stimulus values chosen to “bracket” assumed threshold (5-9)
Stimuli presented many times in random order
“Psychometric function” derived from proportion of ‘yes’ responses
Can be used to measure both detection and discrimination
-Advantages:
Essentially eliminates observer bias
Reduces adaptation
Gives very reliable results
Eliminates errors of anticipation and habituation
-Disadvantages:
Very inefficient and time consuming
Needs preliminary estimate of threshold to decide on stimulus values
2 Modified Methods
Staircase method
Forced choice method
The “Staircase” Methods
The staircase methods represent a compromise between the method of limits and the method of constant stimuli
Efficient
Avoid observer bias
Avoid errors of anticipation and habituation
Forced Choice Methods
Vary location of stimulus among various times or locations
Participant is asked to “locate” the stimulus
Is used in combination with other methods
-Advantages:
Lower thresholds
Avoids observer bias
-Disadvantages:
More stimulus presentations because every trial involves two intervals or locations
Weber
Measuring Subjective Experience
:
the amount of change needed (JND) was a constant proportion (k) of the standard stimulus intensity (I).
Weber’s Fraction: k
Weber’s Law: JND = kI
