jects: Such studies might, for example, provide a basis for comparison of "wild" and "trained" behaviors and their cognitive bases and functions. Studies of "intelligent" behaviors might even suggest the kinds of abilities for which to search in the wild, and allow researchers to uncover capacities heretofore unsuspected.
The communicative and cognitive features which have been shown to exist in these very disparate subjects (at least at the basic levels) are similar enough to suggest that the underlying mechanisms involved in their development, whether or not physically or functionally homologous, are indeed analogous. Understanding any one system may provide useful insights into the understanding of any other, including possibly that of Homo sapiens. Experimental manipulation of the procedures and environments used in animal studies would be ethically unacceptable in work with humans; studies on nonhuman subjects may thus be the means to gain potentially instructive insights into determining the critical variables involved in all systems.
Preparation of this paper was supported by a fellowship from the Harry Frank Guggenheim Foundation; my psittacid research was supported by NSF grants BNS 7912945, BNS 801432, and the Guggenheim Foundation. I thank Kimberley Goodrich, Robert Mitchell, Jan Ramer, Katherine Davidson, Mary Sandhage. Denise Dickson and Bruce Rosen for their assistance with my research, Drs. Diane Reiss and Jeanette Thomas for critical reviews of this manuscript, and Drs. Donald Kroodsma and Luis Baptista for stimulating discussions about their research on avian vocal abilities.
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