To ensure we offer contemporary continuing education opportunities, the CE credit associated with this video is no longer available, however, the video remains available for viewing.Keller and Schoenfeld (1950) offered a unique behavioral perspective on conceptualization and categorization, one that has proven to be dramatically out of step with mainstream cognitive theory. Keller and Schoenfeld's behavioral approach has inspired Dr. Wasserman's research into conceptualization and categorization by nonhuman animals. Using a system of arbitrary visual tokens, Dr. Wasserman and his colleagues have built ever-expanding nonverbal "vocabularies" in pigeons through a variety of different discrimination tasks. Pigeons have reliably categorized as many as 500 individual photographs from as many as 16 different human object categories, even without the benefit of seeing an item twice. Their formal model of categorization effectively embraces 25 years of empirical evidence as well as generates novel predictions for both pigeon and human categorization behavior. Comparative study should continue to elucidate the commonalities and disparities between human and nonhuman categorization behavior; it also should explicate the relationship between associative learning and categorization.