LEXICON SIZE AND ITS RELATION TO FOOT PREFERENCE IN THE AFRICAN GREY PARROT (PSITTACUS-ERITHACUS)

To study footedness in parrots, an international survey of parrot owne rs was conducted. Responses were obtained from 524 individuals, includ ing 70 owners of African Grey parrots (all animals greater than or equ al to 10 months old). All respondents were given a 10-item questionnai re and a standard method for testing foot preference in their pets, an d they were asked to count the number of separate words in their pets' lexicons of human speech sounds. Right-footed African Greys (N=36) ha d significantly larger lexicons than left-footed African Greys (N=34; P=0.01). This difference could not be accounted for by group differenc es in training efforts or socialization/housing with conspecifics. A n on-significant trend in the same direction was found in a comparison s ample of Amazon parrots, although these genera are less adept than Afr ican Greys at learning human speech sounds. Other investigators have p rovided convincing evidence of lateralization, in the avian brain, for the analysis and memory of differing types of stimuli. In addition, t here appears to be preferential left hypserstriatal activation for lon g-term memory consolidation. Our results suggest a relationship betwee n lateral asymmetry for motor preference and asymmetric CNS mediation of a 'higher cognitive' function (i.e. the categorization and long-ter m mnestic processing of human speech sounds). (C) 1997 Elsevier Scienc e Ltd.