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Open Access Publications from the University of California


The International Journal of Comparative Psychology is sponsored by the International Society for Comparative Psychology. It is a peer-reviewed open-access digital journal that publishes studies on the evolution and development of behavior in all animal species. It accepts research articles and reviews, letters and audiovisual submissions.

Volume 12, Issue 3, 1999

Research Article

The Function and Significance of Inter-Species Acoustic Cues in the Transformation of Budgerigar ( Melopsittacus Undulatus ) Sounds Into "Speech"

Analysis of speech-imitation sounds produced by pet budgerigars (Melopsittacus imdulatus) reveals a consistent focus on acoustic components of speech which have counterparts in the species-specific vocalizations of budgerigars. These budgerigar vocalizations include whistle sequences (which, with their rapid glides in pitch contour, need only slight modification to constitute a second-formant representation of speech), the contact call (which is acoustically similar to the secondformant transition of high front vowels), and sounds with harmonic spectra (which can be modified to represent the formant structure of certain vowels). This transformation of species-specific sounds into speech-imitation sounds by focusing on shared acoustic features prompts the hypothesis that, with the appropriate social stimulation, pet budgerigars perceive human speech as modified budgerigar sounds. The hypothesis is supported by the fact that the shared acoustic features are particularly important cues in the perception of species-specific communication sounds by both humans and budgerigars. Such inter-species vocal communication cues, having a common origin somewhere in vertebrate phylogeny. would help to explain the many reported examples of human-like speech perception by nonhuman vertebrates. The shared neural mechanisms which correspond to these shared acoustic patterns could constitute a phylogenetically conservative level of auditory perception which is communication sound-specific but not species-specific.

Decision-Making and Turn Alternation in Pill Bugs ( Armadillidium Vulgare )

Twelve pill bugs ( Armadillidium vulgare, Isopoda, Cmstacean ) were examined in 200 successive T-mazes. When obstacles are present, A. vulgare tend to move by means of turn alternation, which is generally considered an innate adaptive behavior. With a decrease in air moisture, the bugs have a tendency to increase their turn alternation rate. However, in such long successive T-mazes as in this study, continued turn alternation should actually accelerate the bugs' desiccation. This fact implies that turn alternation cannot always work adaptively. In this trade-off situation, while three individuals kept turn alternation at a high rate (1) and four at a low rate, (2), the other five spontaneously increased the rate of turn alternation and then decreased it (3). This instability of turn alternation in group (3) is interpreted as resulting not from stochastic factors but rather from the bugs' own decision-making, and seems to be anescape behavior used to get out of the experimental apparatus. In order to verify thedecision-making hypothesis, all animals were subsequently tested in another successive T-maze apparatus, where the ends of the chosen alleys were shut, i.e., with 50 successive blind alleys. In this situation, while individuals of groups (1) and (2) continued to wander inside the apparatus, those of group (3) found a vertical roughwall, climbed it, and escaped from the apparatus in the middle of the experiment. Mostof the unexercised individuals in the control experiment did not show climbingbehavior

Book Review - Comparative Psychology: A Handbook

by G. Greenberg and M.M. Haraway (Eds.), New York and London: Garland, 1998.