1: Principles of Perceptual Measurement Flashcards
Stimulus
An object or event in the physical world that may be perceived through stimulation of one of the sensory systems
Absolute threshold
The minimum physical intensity that is required for a stimulus to be detected.
Correct rejection
When no stimulus is present in a trial and the subject answers NO.
Criterion
(aka beta) A setpoint or cut off point that is internally established by the subject. On those trials where sensory magnitude exceeds beta, the subject will indicate that a detectable sensory event has occurred and will say YES. If the sensory magnitude fails to reach beta, then the subject will respond NO.
Cross-modality matching
The use of stimuli from different domains to make comparison of the relative magnitude that are produced in different sensory system.
D’ (d prime)
The difference between the means of the noise had signal + noise distributions. According to SDT, d’ can increase either by increasing the strength of the signal or by increasing the sensitivity of the detector.
Difference threshold
The minimum change in physical intensity that is required for a noticeable change in sensation. Difference thresholds are always determined at suprathreshold levels.
Discrimination scaling
The application of difference threshold measurements to estimate sensory magnitude functions. The theoretical foundation for this approach is based on the motion that JNDs represent a constant unit of sensory change, regardless of the actual operating level.
Ekman’s law
The amount of sensory change necessary to produce a JND is not constant, but rather a linear function of the intial or operating level of sensation, This is the physical counterpart to Weber’s law.
False alarm
When no stimulus is present in a trial and the subject says YES.
Fechner’s law
The logarithmic relationship between stimulus intensity and sensation magnitude proposed by Gustav Fechner in 1860.
Function
A mathematical description of how one variable is related to another and generally expressed as a formula. If S represents perceived intensity of sensation and I represents stimulus intensity, then a linear function would have the form S = K x I where k represents the slope of function.
Hit
When a stimulus is present in a trial and the subject says YES
Ideal detector
A detector that can always detect a stimulus and always fails to detect it when it’s a below a certain defined level.
Intramodal matching
Comparing different aspects of a stimulus within a particular sensory domain or modality.
Just noticeable difference JND
A change in sensation that is sufficient to allow that mental event to be just detected.
Magnitude estimation
A psychophysical scaling procedure developed by Stanley Stevens in which human subjects are required to make numerical estimates of the sensory magnitudes that are evoked by stimuli of different physical intensities.