ABSTRACT
Research suggests that for one avian spe cies, the African Grey parrot (Psittacus erithacus), such categorization capacities are far more flexible (Pepperberg, 1983). The subject, Alex, has been taught not only to label many different objects, hues, and shapes but also to understand that “green,” for example, is a par ticular instance of the category “color,” and that, for any object having both color and
shape, specific instances of these attributes (e.g., “green” and “three-corner”) represent different categories. Thus he can categorize objects hav ing one of seven colors and five shapes with respect to either category based on a vocal query of “What color?” or “What shape?” (85.5% accuracy; Pepper berg, 1983). This task tests whether the subject can comprehend the categorical concept rather than simply sort ob jects into categories. Because Alex is often re quired to categorize the same exemplar with respect to shape at one time and color at an other, the task also involves flexibility in chang ing the basis for classification. Such flexibility, or capacity for re-classification, is thought to indicate the presence of an “abstract aptitude” similar to that demonstrated by chimpanzees (Hayes Sc Nissen, 1952/1971).
