Chapter 1 Flashcards
Steps in the perceptual process
1) stimulus in environment
2) light is reflected and transformed
3) receptor processes
4) neural processing
5) perception recognition action
Principle of transformation
Stimuli and responses created by stimuli are transformed/changed between the environmental stimulus and perception (1st transformation occurs when light enters the eye, is focused by the optical system, and forms the image on the retina)
Principle of representation
perception is based on representations of stimuli formed on receptors and on activity in the nervous system, not direct contact with stimuli
Transduction
conversion of one form of energy into another, i.e. physical energy (light) into electrical signals (neural impulses)
sensory receptors
cells specialized to respond to environmental energy
visual pigment
visual receptors use light sensitive chemicals called visual pigments to transform light into electrical energy
neural processing
network of neurons transmits/changes/processes signals from receptors to retina to brain to within the brain
cerebral cortex
contains primary receiving areas for senses in:
- occipital lobe - vision
- temporal lobe - hearing
- parietal lobe - feeling/skin sensations
- frontal lobe - receives from all senses and helps to coordinate perception involving 2 or more senses
perception
conscious awareness of stimulus (i.e. a tree)
recognition
categorizing stimulus (i.e. naming stimulus “tree” to give meaning)
visual field agnosia
Inability to recognize objects (i.e. Dr. P, the man who mistook his wife for a hat, could perceive some parts of object but could not organize/perceptually assemble these parts in a way that enabled him to recognize the object as a whole)
action
motor activities
knowledge
any information that the perceiver brings to a situation
rat-man demonstration
shows how recently acquired knowledge influences perception
bottom-up/data-based processing
processing based on incoming data/stimuli reaching the processors
top-down/knowledge based processing
processing based on knowledge/ labelling a perception based on prior knowledge (not necessarily involved in perception of very small quick stimuli)
psychophysical approach/psychophysics
measures relationship between stimuli and behaviour response
oblique effect
better detail vision for vertical/horizontal lines compared to slanted lines
physiological approach
measures relationship between stimuli and physiological responses and relationship of physiological and behavioural responses
cognitive influences on perception
knowledge, memories, expectations brought to a situation that may influence perception
absolute threshold
minimum stimulus intensity that can be detected
classical psychophysical methods
3 main methods for measuring/determining thresholds by limits, adjustment and constant stimuli developed by Fechner (1860)
Method of limits
classical psychophysical method - experimenter presents stimuli in increasing or decreasing order to find threshold - repeated multiple times from both top and bottom and results averaged
Method of adjustment
classical psychophysical method - fastest - stimulus intensity +/- with a knob by observer until just detectable (done multiple times and results averaged)
Method of constant stimuli
classical psychophysical method - experimenter presents 5-9 stimuli with different intensities in random order and observer replies “yes/no” (intensities are chosen so that lowest is never perceived and highest is always perceived). Threshold is determined by intensity perceived in 50% of trials (most accurate but time consuming)
difference threshold (just noticeable difference)
Weber - minimum difference between two stimuli before we can perceive difference
Weber’s Law
Weber’s law states that the just-noticeable difference between two stimuli is proportional to the magnitude of the stimuli, or, an increment is judged relative to the previous amount
Weber Fraction
Generally the ration of difference threshold to the standard is constant (for weight it is 0.02) i.e. if 105 g can (only just) be distinguished from that of 100 g, the JND (or difference threshold) is 5 g, if the mass is doubled, the difference threshold also doubles (to 10 g), so that 210 g can be distinguished from 200 g
magnitude estimation
experimenter presents standard/moderate stimuli and assigns it a value of 10, then presents other stimuli and observer assigns values proportionally
response compression
increase in perceived magnitude is less than intensity (doubling the physical intensity of a stimulus less than doubles the subjective magnitude of the stimulus)
response expansion
increase in perceived magnitude is greater than intensity (doubling the physical intensity of a stimulus more than doubles the subjective magnitude of the stimulus)
Power functions
relationship between perceived intensity and magnitude - Steven’s power law, P=KS^n where P=perceived, K= constant, S= stimulus intensity. n1.0= response expansions i.e. electric shock
phenomenological method
a person describes what they are perceiving or indicates when a perticular perception occurs
signal detection theory
detection of stimulus relies on both sensitivity and response criterion
visual search
find one stimulus among many as quickly as possible
reaction time
time between presentation of and reaction to a stimulus
response criterion
if low threshold for response - more yes answers, if high threshold for response - more no answers
hit
correct response - saying yes when a stimulus is present
miss
incorrect response - saying no when a stimulus is present
false alarm
incorrect response - saying yes when no stimulus is present
correct rejection
correct response - saying no when no stimulus is present
payoffs
inducements to answer a particular way in a signal detection experiment
Receiver Operating Characteristic
a curve on a plot where subjects are tested using different payoff criteria to induce different levels of correct/incorrect answers. If participant answers lie on the curve at each criteria, it is clear that they have the same sensitivity.
