The Staircase Procedure for Finding a Perceptual Threshold

Overview

Source: Laboratory of Jonathan Flombaum—Johns Hopkins University

Psychophysics is the name for a set of methods in perceptual psychology designed in order to relate the actual intensity of stimuli to their perceptual intensity. One important aspect of psychophysics involves the measurement of perceptual thresholds: How bright does a light need to be for a person to be able to detect it? How little pressure applied to the skin is detectable? How soft can a sound be and still be heard? Put another way, what are the smallest amounts of stimulation that humans can sense? The staircase procedure is an efficient technique for identifying a person's perceptual threshold.

This video will demonstrate standard methods for applying the staircase procedure in order to identify a person's auditory threshold, that is, the minimal volume necessary for a tone to be perceived.

Procedure

1. Stimuli and Equipment

This experiment will require a computer with basic experimental software as well as a set of headphones and a relatively quiet testing room (sound proofing is not necessary).
The stimuli in the experiment will be tones of with frequencies of 1 kHz, 2 kHz, 3 kHz, 4 kHz, 5 kHz and 6 kHz. Human hearing is best within this frequency range.
During the course of the experiment, the volume of the tones will be varied adaptively in the range of 1 to 40 dB, as will be clear

Results

The aim of the staircase procedure is to bring the participant to a volume at which they can just barely hear a tone. This is achieved by prompting a series of 'No' responses in the first few trials. Once a 'Yes' response is produced, the goal is to keep the volume played close to the one that elicited the first 'Yes'. This is done by lowering the volume whenever a 'Yes' response is given. This produces a pattern in which the volume rises steadily in the first few trials, and then plateaus

Application and Summary

One of the primary applications of the auditory staircase procedure is to assess hearing impairment. Beyond normal aging, hearing impairments can be caused by damage to the inner ear, brain damage, and disease. Often, hearing impairment affects particular frequencies more than others. The staircase method can be used to determine whether someone possesses especially poor hearing within a narrow frequency range, which would suggest hearing impairment caused by more than normal aging. Figure 6 graphs audit

References

Drake-Lee, A. B. (1992). Beyond music: auditory temporary threshold shift in rock musicians after a heavy metal concert. Journal of the royal society of medicine, 85(10), 617-619.