Exam 2: Chapter 2 Flashcards
The Scoville scale
is a psychophysical scale that measures our experience of piquancy or “hotness”. The more capsaicin is present in a particular food, the spicier it will taste.
Scoville scale:
a measure of our detection of the amount of an ingredient called capsaicin in chili peppers.
Capsaicin:
the active ingredient in chili peppers that provides the experience of hotness, piquancy, or spiciness.
Psychophysical scale:
a scale on which people rate their psychological experiences as a function of the level of a physical stimulus.
Scales are used to match changes in the physical amount of a stimulus with corresponding psychological changes in perception of the stimulus. Most often not linear.
exceptions: lines; coldness
Method of limits:
Stimuli are presented in a graduated scale, and participants must judge the stimuli along a certain property that goes up or down.
Method of constant stimuli:
a method whereby the threshold is determined by presenting the observer with a set of stimuli, some above threshold and some below it, in a random order.
Method of adjustment:
a method whereby the observer controls the level of the stimulus and “adjusts” it to be at the perceptual threshold.
Magnitude estimation:
a psychophysical method in which participants judge and assign numerical estimates to the perceived strength of a stimulus.
Signal detection theory:
the theory that in every sensory detection or discrimination, there is both sensory sensitivity to the stimulus and a criterion used to make a cognitive decision.
Catch trial:
a trial in which the stimulus is not presented – used to check a study participant’s accuracy and honesty.
Forced-choice method:
a psychophysical method in which a participant is required to report when or where a stimulus occurs instead of whether it was perceived. Technique prevents the need for catch trials because the observer can’t say yes in every trial, regardless of the presence of a stimulus.
Psychophysics:
study of the mathematical relationship between magnitude changes in physical stimuli and the resulting psychological perception
Detection:
minimum intensity that we can perceive (absolute thresholds)
example) a dog can smell blood better than a human
Discrimination:
minimum change in stimulus need to separate two stimuli (difference thresholds)
(looking at the change)
Scaling:
correlation of changes in magnitude between physical stimulus and psychological experience
sensation magnitude vs stimulus intensity graph
exponent is <1: exponential increase (example: electric shock- has a survival value)
exponent =1: linear (apparent length)
exponent < 1: concave ( brightness) (I think this is similar for audio and visual)
—visian and sound are NONlinear
when take the log: the electric shock will be greatest intensity
we think the curve is like this so we can see a wieder range of stimulus
Absolute threshold:
minimum of a stimulus required for detection
-of humans- no cut off point
look @ 50% mark for where can detect stimulus – finding the middle range
differing values for the threshold indicate that humans have top-down processing
see graph- be able to find on graph
can find experimentally through the method of descending limits: ex) making each light dimmer
—–method of limits
or methods of constant stimuli
theoretical threshold
stepwise- what a machine would give (ideal)
The method of limits
The participant must decide if a stimulus is present at a number of different levels of intensity. The stimulus is increased in even trials and decreased in odd trials. A Y indicates that the participant detects the stimulus, whereas an N indicates that the participant does not detect the stimulus.
The estimate of the threshold is considered to be the mean crossover point.
Threshold = mean crossover = 4.5
Average result of ascending and descending trails for absolute threshold
Ascending and Descending trials; errors of habituation and anticipation (subject learns pattern)
Difference threshold (the JND) Ascending series and Descending series Crossover point Two-point touch threshold
Difference threshold (JND):
Just-noticeable difference (JND), or the smallest difference between two stimuli that can be detected.
Ascending series:
a series in which a stimulus gets increasingly larger along a physical dimension.
start with canNOT see the light, until they can
note: will get slightly different answers between ascending and descending series
Descending series:
a series in which a stimulus gets increasingly smaller along a physical dimension.
start with a bright light and lower intensity
problem: can figure out the pattern; decreasing at a regular rate
note: will get slightly different answers between ascending and descending series
Crossover point:
the point at which a person changes from detecting to not detecting a stimulus or vice versa.
Two-point touch threshold:
the minimum distance at which two touches are perceived as two touches and not one.