Comparing performance of humans and pigeons in rule-based visual categorization tasks

We report two experiments which compare performance of pigeons and humans in rule-based categorization tasks with Gabor stimuli that varied in frequency and orientation. For different tasks, accurate responding depended on frequency while orientation varied but was non-relevant; or on orientation while frequency varied but was non-relevant. Results showed that humans learned both tasks faster than pigeons, with abrupt increases in accuracy that were indicative of rule-based responding, while pigeons learned the tasks gradually. In the frequency-relevant task, humans responded at near-optimal levels whereas accuracy for pigeons decreased when orientation was near vertical. These results suggest that humans are more adept than pigeons at solving categorization tasks that are facilitated by selective attention. However, both species responded suboptimally in the orientation-relevant task, with decreased levels of accuracy for exemplars with frequencies that were outside the middle of the range. Some processes mediating visual categorization of Gabor stimuli by humans and pigeons may be similar, despite functional and neuroanatomical differences.