Auditory reaction time and the derivation of equal loudness contours for the monkey.
Reaction time can draw an equal-loudness map, and the monkey map peaks near 1000 cps no matter what reinforcer you use.
01Research in Context
What this study did
Scientists played tones of different loudness and pitch to monkeys.
They measured how fast each monkey lifted its hand after the tone.
By linking speed to loudness they drew ‘equal-loudness’ curves, like an audiogram made from reaction time.
What they found
The monkeys reacted fastest to tones near 1000 cps.
Louder tones always got faster lifts, but the curves showed a clear sweet spot around 1000 cps.
How this fits with other research
Schwartz et al. (1971) later added food rewards and showed the same latency sweet spot, proving the curve stays put under reinforcement.
Winton (1975) swapped food for mild shock and still got matching loudness contours, so the shape is not a reward trick.
Goldman et al. (1979) ran a similar test with rats and also found latency more stable than yes-no answers, backing the 1966 choice of measure.
Why it matters
If you ever need a quick hearing check for a non-verbal client, watch reaction time instead of asking ‘Did you hear it?’ Latency gives a clearer picture and works even when the person can’t name the sound. Try pairing a favorite item with the tone and time the reach; the speed curve will tell you which pitches and volumes are truly detected.
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Join Free →Pick a preferred item, pair it with tones across frequencies, and time the reach—plot latency to see the client’s true auditory sweet spot.
02At a glance
03Original abstract
Monkeys were trained to release a telegraph key at the onset of a pure tone. Latency of the response was measured over a 70-db range of sound pressure (re 0.0002 dyn/cm(2)) at six frequencies (250 to 15,000 cps). Latency was found to be an inverse exponential function of intensity at all frequencies. Equal loudness was inferred from the equal latency contours which were constructed from the latency-intensity functions at each frequency. These data indicate peak auditory sensitivity for the monkey near 1000 cps. At the frequencies above and below 1000 cps consistently more sound energy was required for equal latency.
Journal of the experimental analysis of behavior, 1966 · doi:10.1901/jeab.1966.9-135