Detection of increments in noise intensity by monkeys.
Monkeys obey Weber's law when detecting noise increments, so background intensity and signal probability will shape your client's auditory discrimination too.
01Research in Context
What this study did
Researchers tested how well monkeys notice tiny jumps in white-noise loudness.
Each monkey pressed a lever when it heard the noise get slightly louder.
The team varied how often the louder sound happened to see if that changed the monkey's choices.
What they found
The monkeys followed Weber's law: the bigger the background noise, the bigger the jump had to be for them to notice.
When louder sounds were rare, the animals stayed quiet; when common, they pressed more, showing a clear response bias.
How this fits with other research
Azrin (1958) said loud steady noise does not hurt human performance; Clopton (1972) adds that monkeys still detect tiny changes in that noise.
Rincover et al. (1975) found monkeys have strong color likes that refuse to fade; here, noise detection stays stable too, showing tight stimulus control across senses.
CASSOTTA et al. (1964) used noise as punishment, while M used noise as a signal to watch—same sound, opposite jobs, proving noise can serve many behavioral functions.
Why it matters
Weber's law works for monkeys hearing noise, just like it works for kids seeing lights or feeling weights.
When you set up auditory discrimination tasks, expect the same jump in intensity to be harder to notice if the background is already loud.
Also, remember that how often the "target" sound appears can sway response bias—balance target rates in probe sessions to keep data clean.
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02At a glance
03Original abstract
Monkeys were trained to detect 100-msec increments in the intensity of continuous white noise. A response on one of two bars was reinforced with some probability if it conformed to the presence or absence of the increment on that trial. Stimulus parameters of background intensity, increment size, and probability of increment presentation were varied, and response probabilities and latencies were recorded. The task was analogous to the "yes-no" task used in human psychophysics. Data analysis within the context of signal-detection theory revealed response biasing toward one bar or the other to be related to the probability of increment presentation, whereas sensitivity depended on the combination of increment size and background noise intensity. Weber's law was found to hold for a large range of background intensities in that the sensitivity to relative intensity increments varied little. Performance was compared to that of an ideal observer that uses samples of the envelope of the noise waveform on which to base its responses.
Journal of the experimental analysis of behavior, 1972 · doi:10.1901/jeab.1972.17-473