Pigeons show efficient visual search by category: effects of typicality and practice

Three experiments investigated category search in pigeons, using an artificial category created by morphing of human faces. Four pigeons were trained to search for category members among nonmembers, with each target item consisting of an item-specific component and a common component diagnostic of the category. Experiment 1 found that search was more efficient with homogeneous than heterogeneous distractors. In Experiment 2, the pigeons successfully searched for target exemplars having novel item-specific components. Practice including these items enabled the pigeons to efficiently search for the highly familiar members. The efficient search transferred immediately to more typical novel exemplars in Experiment 3. With further practice, the pigeons eventually developed efficient search for individual less typical exemplars. Results are discussed in the context of visual search theories and automatic processing of individual exemplars.