title: Coding in pigeons: Multiple-coding versus single-code/default strategies.
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.
authors.affiliation: University of Minho.
authors.forename: Carlos
authors.initials: C
authors.lastname: Pinto
authors.affiliation: University of Minho.
authors.forename: Armando
authors.initials: A
authors.lastname: Machado
mesh_terms: D000818:Animals; D010856:Columbidae; D003216:Conditioning, Operant; D004193:Discrimination Learning; D004192:Discrimination, Psychological; D005793:Generalization, Psychological; D008960:Models, Psychological; D012153:Retention, Psychology
keywords: delayed matching-to-sample; many-to-one matching; pigeons; timing