Footedness in parrots: three centuries of research, theory, and mere surmise.

In contemporary debates about laterality in animals, the parrot (Psittaciformes) is often cited as an exemplar--possibly unique--of laterality in limb function at the population level comparable in kind and strength to handedness in man. This conclusion rests on just two reports (Friedman & Davis, 1938; Rogers, 1980) that most species of parrots are left-footed, that is, that they preferentially perch on the right foot and hold food with the left. In fact, speculation about and scientific study of laterality in parrots go well beyond these two investigations. The question itself dates from at least the 17th century, after which, beginning in the 1860s, it became the subject of broad interest and debate. In our own time, it also has continued to occupy the attention of at least a small number of ornithologists and field biologists whose work, like that of their predecessors, is not cited in the current neuropsychological literature on this topic. To fill out the historical as well as contemporary record for consideration by neuropsychologists today, these other observations and theoretical analyses are reviewed, and new questions about laterality in parrots raised by this work are presented.