“Acquisition of the Same/Different Concept by an African Grey Parrot (Psittacus erithacus): Learning with Respect to Categories of Color, Shape, and Material”

This is a seminal article in Pepperberg’s research on Grey parrots. “An African Grey parrot, previously taught to use vocal English labels to discriminate more than 80 different objects and to respond to questions concerning categorical concepts of color and shape, was trained and tested on relational concepts of same and different. The subject, Alex, replied with the correct English categorical label (“color,” “shape,” or “mah-mah” [matter]) when asked “What’s same?” or “What’s different?” about pairs of objects that varied with respect to any combination of attributes. His accuracy was 69.7%–76.6% for pairs of familiar objects not used in training and 82.3%–85% for pairs involving objects whose combinations of colors, shapes, and materials were unfamiliar. Additional trials demonstrated that his responses were based upon the question being posed as well as the attributes of the objects. These findings are discussed in terms of his comprehension of the categories of color, shape, and material and as evidence of his competence in an exceptional (non-species-specific) communication code.”