Acquisition and maintenance of delayed matching‐to‐sample in tufted capuchin monkeys
Grow delay and inter-trial break together to keep delayed matching accuracy above a large share even at 90-second waits.
01Research in Context
What this study did
Colares Leal and colleagues worked with two tufted capuchin monkeys.
They taught the monkeys a delayed matching-to-sample game on a touch screen.
The team slowly made the game harder by stretching both the delay and the break between trials.
What they found
Both monkeys still picked the correct picture a large share of the time even when the delay hit 90 seconds.
Accuracy stayed high when the break between trials was at least as long as the delay.
If the break was shorter than the delay, accuracy dropped.
How this fits with other research
The result lines up with Kimball et al. (2023) and Malouff et al. (1985).
All three used single-case lab setups to see how reinforcement timing controls choices.
Baum (2025) adds theory: longer breaks give the brain time to "reset," which matches the higher accuracy seen here when ITI matched or beat the delay.
Why it matters
When you train delayed matching with clients, grow the wait time and the inter-trial break together.
Keep the break equal or longer than the delay to protect accuracy.
This simple tweak can push memory past the usual 10-second ceiling without extra prompts.
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02At a glance
03Original abstract
Delayed matching-to-sample (DMTS) is a commonly used procedure to investigate short-term memory. For the study of functions of forgetting, the delay between the disappearance of the sample stimulus and appearance of choices is manipulated. The intertrial interval (ITI) is also varied to assess interference effects. Performance decrements have been observed as delay increases and, in some cases, performance recovery occurs when ITIs are increased. Other studies indicate that the higher the ITI/delay ratio, the greater the accuracy in DMTS. In this study, 2 experiments investigated DMTS performances of 3 tufted capuchin monkeys as function of delay and ITI. In Experiment 1, alternation of gradual increases of delay and ITI was effective in producing ≥90% accuracy at delays as long as 90 s. Individual monkeys differed in the highest value of delay at which this criterion was met. In Experiment 2, the monkeys were exposed to 5-s DMTS with different ITIs to assess the effects of various ITI/delay ratios on accuracy. Highest accuracy tended to occur at the higher ITI/delay ratios.
Journal of the Experimental Analysis of Behavior, 2020 · doi:10.1002/jeab.599