Perception of acoustic stress patterns across species: humans, budgerigars, and rats

Perception of acoustic stress patterns across species: humans, budgerigars, and rats

Marisa Hoeschele1 and Juan M. Toro 2, 3

1. University of Vienna, Austria

2. Center for Brain and Cognition, Universitat Pompeu Fabra, Spain

3. ICREA

The ability to perceive lexical stress, the apparent “strength” of some syllables relative to others, is important because it can help a listener segment speech and distinguish the meaning of words and sentences. Very little is known, however, whether these abilities are human specific, or whether we can find them in other species. We used a go/nogo operant paradigm to compare humans to budgerigars (Melopsittacus undulatus) and rats (Rattus norvegicus) in their ability to distinguish trochaic (stress-initial) from iambic (stress-final) nonsense words. We chose budgerigars as a comparison because they are vocal learners, like humans, and we chose rats because they are more closely-related to humans, but are not vocal learners. Once the three species learned the task, we presented novel words and also words that had certain cues removed (e.g., pitch) to determine which cues were most important in stress perception. All three species learned the task and generalized the discrimination to nonsense words they had never heard before. However, when some cues of lexical stress were removed, humans were the least impaired, followed by budgerigars, and rats were no longer able to solve the task. This suggests that vocal learning may be relevant for processing prosodic information.