Coding in pigeons: Multiple-coding versus single-code/default strategies.
Pigeons blend many memory codes instead of sticking to one rule, so watch for strategy shifts in your own learners.
01Research in Context
What this study did
Pinto et al. (2015) tested pigeons on a delayed matching-to-sample task. The birds had to remember a hue for a few seconds, then pick the same hue from two choices.
The team wanted to know if the birds used one simple rule or many rules to solve the task. They tracked choice patterns across many trials.
What they found
The pigeons did not follow a single rule. Some trials looked like they used many codes, others like they used one code.
The data landed in the middle: neither pure multiple-coding nor pure single-code models fit every test. The birds switched tactics.
How this fits with other research
Green et al. (1987) already showed that position cues speed up temporal learning in pigeons. Carlos adds that even after learning, the birds keep flexible codes, not one fixed rule.
Arantes et al. (2008) pitted two timing models against each other and found context shifts choice. Carlos finds the same pattern in hue memory: context nudges the birds toward or away from a single-code rule.
Dougherty et al. (1996) used presence-versus-absence trials to show signal-detection beats discrete-state models. Carlos extends the idea: signal timing also needs a hybrid account, not an either-or label.
Why it matters
Your learners, like pigeons, may hold several rules at once. If a child with autism solves a delay task one way today and another tomorrow, it is not error—it is flexibility. Probe with varied cues, track shifts, and reinforce the strategy that works in each context.
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02At a glance
03Original abstract
To investigate the coding strategies that pigeons may use in a temporal discrimination tasks, pigeons were trained on a matching-to-sample procedure with three sample durations (2s, 6s and 18s) and two comparisons (red and green hues). One comparison was correct following 2-s samples and the other was correct following both 6-s and 18-s samples. Tests were then run to contrast the predictions of two hypotheses concerning the pigeons' coding strategies, the multiple-coding and the single-code/default. According to the multiple-coding hypothesis, three response rules are acquired, one for each sample. According to the single-code/default hypothesis, only two response rules are acquired, one for the 2-s sample and a "default" rule for any other duration. In retention interval tests, pigeons preferred the "default" key, a result predicted by the single-code/default hypothesis. In no-sample tests, pigeons preferred the key associated with the 2-s sample, a result predicted by multiple-coding. Finally, in generalization tests, when the sample duration equaled 3.5s, the geometric mean of 2s and 6s, pigeons preferred the key associated with the 6-s and 18-s samples, a result predicted by the single-code/default hypothesis. The pattern of results suggests the need for models that take into account multiple sources of stimulus control.
Journal of the experimental analysis of behavior, 2015 · doi:10.1002/jeab.153