Perception: L3-4 Signal detection theory

Signal

the true sensory information coming from the external world

Noise

e various physiological or psychological processes influencing our perception of that external stimulus in an unpredictable manner

Signal

the true sensory information coming from the external world

Noise

e various physiological or psychological processes influencing our perception of that external stimulus in an unpredictable manner

physiological noise

caused by spontaneous activity in our sensory nerves

psychological noise

could be spontaneous fluctuations in attention that alter the perception of sensory stimuli in an unpredictable manner

Statistical perspective of noise

whatever is not measured and that contributes variability to participants' responses

sensitivity (signal detection theory)

refers to an individual's ability to distinguish between signal and noise, reflecting how well they can detect a target stimulus. Higher = better discrimination

Criterion

the decision threshold set by an individual in SDT, determining whether they report the presence of a signal. It reflects their response bias, influenced by factors like expectations or consequences of false alarms and mises

hit

the signal is present and you say it is present

miss

the signal is present and you say it is not present

false alarm

the signal is not present and you say it is present

correct rejection

the signal is not present and you say it is not present

What would happen to your criterion if the experimenter threatened to kill you for saying that a stimulus is present when there is no stimulus?

Less inclined to say "yes" -> move the criterion to the right on the distribution graph

receiver operating characteristic (ROC) curve

Plots hit rates against false alarm rates. Each line represents a particular level of sensitivity, and different points on a given line represent different response criteria at the same level of sensitivity. If the point is more to the left of the curve, the criterion is moved to the right on the normal distribution graph, and this means that the person is more strict.

SDT allows to...

estimate participants' sensitivity (d') and criterion (c) as a function of their specific ratio of hits and false alarms