Biases in pigeon working memory

The psychophysics and short-term retention of pigeons’ responses to rate of stimulus change were assessed in two experiments, using a symbolic delayed matching-to-sample procedure. In Experiment 1, the birds discriminated between steady and flickering lights. Psychophysical assessments of the discrimination suggested a mix of analogical and categorical strategies. Retention tests revealed a consistent bias to respond to the choice associated with theflickering sample. In Experiment 2, the birds discriminated between different rates of stimulus change (slow vs.fast). Retention tests indicated a bias to respond to the alternative associated with theslow sample. Transfer tests to new stimulus values revealed that the birds processed the stimuli in an absolute, rather than a relational fashion. These findings are related to recent work on biased forgetting in animal working memory experiments.