Psychophysical Adaptive Procedure: Developing a New, Generalizable Method
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“Staircasing” is a classic experimental procedure used in psychophysics wherein when a subject successfully discriminates between two stimuli that differ on one perceptual dimension, the stimuli become more similar to each other on that dimension, and when the subject fails, the stimuli become more different. The purpose of this procedure is to find the size of the difference that produces a specific level of discrimination success. Traditional staircase procedures require subjects to be run individually for many trials. Our goal was to develop a procedure for crowd-sourced online data collection in which subjects can be tested simultaneously using only a few trials each with every new piece of data altering the stimulus pair shown on the next trial. We do this by continually fitting subject responses to a plausible function that is used to predict the difference that should produce the desired accuracy level. Only presenting differences predicted to yield the desired performance allows us to find the difference corresponding to this accuracy level faster than sampling the whole range of stimulus differences. The stimulus values we determined with this method were used for research on the phenomenon of learned categorical perception. We present this new technique as an efficient way of determining psychophysical values more generally for purposes of controlling stimulus discriminability in experimental research.