Sensation & Perception: Psychophysics

14 flashcards · Biology · by lakesare

Bottom-up processing VS top-down processing?
Bottom-up processing - is processing that is based on incoming data. Incoming data always provide the starting point for perception because without incoming data, there is no perception. For Ellen, the incoming data are the patterns of light and dark on her retina created by light reflected from the moth and the tree. Top-down processing - is processing that is based on knowledge. For Ellen, this knowledge includes what she knows about moths. Perception is determined by an interaction between b…
What's: psychophysical approach to perception, VS physiological approach to perception?
psychophysical approach - for example, asking an observer to decide whether two very similar colors are the same. physiological approach - 1. measure the relationship between physiological processes and stimuli, 2. or between physiological processes and perception. The psychophysical approach to perception was introduced by Gustav Fechner, a physicist who, in his book Elements of Psychophysics (1860/1966), coined the term psychophysics to refer to the use of quantitative methods to measure rela…
Explain these 3 pictures:
a. PP - PsychoPhysical approach (stimulus & perception) b. PH 1 - PHysiological approach (physiology & stimulus) c. PH 2 - PHysiological approach (physiology & perception) Experiments that measure the relationships indicated by the arrows in Figure (a) The psychophysical relationship (PP) between stimulus and perception: Two colored patches are judged to be different.(b) The physiological relationship (PH1) between the stimulus and the physiological response: A light generates a neural response…
Explain 3 methods for determining the absolute threshold: method of limits method of adjustment method of constant stimuli The choice among the methods of limits, adjustment, and constant stimuli is usually determined by the accuracy needed and the amount of time available. The method of constant stimuli is the most accurate method because it involves many observations and stimuli are presented in random order, which minimizes how presentation on one trial can affect the observer’s judgment of…
In the method of limits, the experimenter presents stimuli in either ascending order or descending order, and the mean is taken. The results of an experiment to determine the threshold using the method of limits. The dashed lines indicate the crossover point for each sequence of stimuli. The threshold—the average of the crossover values—is 98.5 in this experiment. In the method of adjustment, the person adjusts the knob on their own. The observer or the experimenter adjusts the stimulus intensi…
Absolute threshold VS difference threshold?
The absolute threshold is the smallest amount of stimulus energy necessary to detect a stimulus. For example, the smallest amount of light energy that enables a person to just barely detect a flash of light would be the absolute threshold for seeing that light. The difference threshold is the smallest difference between two stimuli that a person can detect.
What does DL stand for?
Difference Threshold. From the German Differenze Limen, which is translated as 'difference threshold'.
How is Weber fraction calculated? Ernst Weber (1795– 1878), a physiologist who, a few years before the publication of Fechner’s book, measured another type of threshold, the difference threshold.
Weber fraction is the ratio of Difference Threshold (DL) to the weight of the standard: DL/100g = 2g/100g = 0.02.
What's Weber's law? Ernst Weber (1795– 1878), a physiologist who, a few years before the publication of Fechner’s book, measured another type of threshold, the difference threshold.
Weber's law states that, over a large range of intensities, the Weber fraction is constant. The Weber fraction remains relatively constant for a particular sense, but each type of sensory judgment has its own Weber fraction. For example, from Table 1.1 we can see that people can detect a 1 percent change in the intensity of an electric shock but that light intensity must be increased by 8 percent before they can detect a difference. (a) The person can detect the difference between a 100-gram st…
What's meant by response criterion?
It's whether someone is a: conservative responder like Regina, who says 'yes, I see the light' only if she is very sure she sees the light, or a liberal responder like Julie, who says 'yes' any time she thinks the light might possibly have been presented. Criterion is a measure of the willingness of a respondent to say 'Signal Present' in an ambiguous situation.
What's response compression VS response expansion?
response compression - doubling the actual intensity doesn't increase the perceived intensity by 2. For example, when intensity is 20, perceived brightness is 28. If we double the intensity to 40, perceived brightness does not double, to 56, but instead increases only to 36. response expansion - doubling the actual intensity more than doubles the perceived intensity. The electric shock curve bends up, indicating that doubling the strength of a shock more than doubles the sensation of being shoc…
What does SDT stand for?
Signal Detection Theory
What does a person do when they must choose whether loudness 20 is just Noise or Signal + Noise?
Person's choice depends on their criterion. liberal neutral conservative
Explain the picture
Liberal, neutral, conservative. Respond “yes” (“I detect the stimulus”) when the perceptual effect is greater than the criterion, and respond “no” (“I do not detect the stimulus”) when the perceptual effect is less than the criterion.
What does ROC stand for in ROC curve?
Receiver Operating Characteristic