Heidi Lyn received her Ph.D. from Georgia State University where she did her dissertation on the semantic categorization of lexigram-competent apes, revealed in their lexical errors. She has published on the development of symbolic representation in apes, as manifest in both play and communication, and on the communicative and cognitive behaviors of sea mammals such as dolphins, belugas, and walrus. She has held positions at UCLA, the New York Aquarium and the Sea Mammal Research Unit of the School of Biology, St. Andrews University, Scotland.