Auditory delayed matching in the bottlenose dolphin.
Delayed auditory matching stays perfect at two-minute delays only if the sample lasts longer than 0.2 seconds.
01Research in Context
What this study did
One bottlenose dolphin played an auditory matching game.
The animal heard a sound, waited up to two minutes, then picked the matching sound from two choices.
Researchers slowly lengthened the wait to see how long the dolphin could remember the sample.
What they found
The dolphin scored 100 % correct across 169 trials with delays as long as 120 seconds.
When the sample sound lasted 0.2 seconds or less, accuracy dropped to chance level.
Short samples wiped out the dolphin’s perfect memory.
How this fits with other research
Davison et al. (1995) ran the same game with hens. They also saw accuracy rise when sample duration increased from 2 to 10 seconds, showing the 0.2-second floor found in the dolphin still holds across species.
Hanson et al. (2021) and Zhelezoglo et al. (2021) moved the task to humans. They used go/no-go successive matching and built full auditory equivalence classes, proving the dolphin’s simple delay task can grow into language-like networks in people.
Madden et al. (2003) added overt naming during visual matching. Naming boosted human accuracy, something the dolphin could not do, highlighting why humans can keep long delays even with shorter samples.
Why it matters
The 0.2-second sample rule still guides your task design today. When you run auditory matching with learners, keep each sample longer than half a second and let them name or repeat it if they can. If you see errors, lengthen the sound before you shorten the delay.
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02At a glance
03Original abstract
A bottlenose dolphin, already highly proficient in two-choice auditory discriminations, was trained over a nine-day period on auditory delayed matching-to-sample and then tested on 346 unique matching problems, as a function of the delay between the sample and test sounds. Each problem used new sounds and was from five to 10 trials long, with the same sound used as the sample for all trials of a problem. At each trial, the sample was projected underwater for 2.5 sec, followed by a delay and then by a sequence of two 2.5-sec duration test sounds. One of the test sounds matched the sample and was randomly first or second in the sequence, and randomly appeared at either a left or right speaker. Responses to the locus of the matching test sound were reinforced. Over nine, varying-sized blocks of problems, the longest delay of a set of delays in a block was progressively increased from 15 sec initially to a final value of 120 sec. There was a progressive increase across the early blocks in the percentage of correct Trial 1 responses. A ceiling-level of 100% correct responses was then attained over the final six blocks, during which there were 169 successive Trial 1 responses bracketed by two Trial 1 errors (at 24- and 120-sec delays). Performance on trials beyond the first followed a similar trend. Finally, when the sample duration was decreased to 0.2 sec or less, matching performance on Trial 1 of new problems dropped to chance levels.
Journal of the experimental analysis of behavior, 1974 · doi:10.1901/jeab.1974.21-19