Psychology
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Item The structure and perception of budgerigar (Melopsittacus undulatus) warble songs(2009) Tu, Hsiao-Wei; Dooling, Robert J; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The warble song of male budgerigars (Melopsittacus undulatus) is an extraordinarily complex, multi-syllabic, learned vocalization that is produced continuously in streams lasting from a few seconds to a few minutes without obvious repetition of particular patterns. As a follow-up of the warble analysis of Farabaugh et al. (1992), an automatic categorization program based on neural networks was developed and used to efficiently and reliably classify more than 25,000 warble elements from 4 budgerigars. The relative proportion of the resultant seven basic acoustic groups and one compound group is similar across individuals. Budgerigars showed higher discriminability of warble elements drawn from different acoustic categories and lower discriminability of warble elements drawn from the same category psychophysically, suggesting that they form seven perceptual categories corresponding to those established acoustically. Budgerigars also perceive individual voice characteristics in addition to the acoustic measures delineating categories. Acoustic analyses of long sequences of natural warble revealed that the elements were not randomly arranged and that warble has at least a 5th-order Markovian structure. Perceptual experiments provided convergent evidence that budgerigars are able to master a novel sequence between 4 and 7 elements in length. Through gradual training with chunking (about 5 elements), birds are able to master sequences up to 50 elements. The ability of budgerigars to detect inserted targets taken in a long, running background of natural warble sequences appears to be species-specific and related to the acoustic structure of warble sounds.Item The influence of context on categorization decisions for mental health disorders(2009-07) Marsh, Jessica K.; De Los Reyes, AndresMental health clinicians engage in an important form of real world categorization as they diagnose their patients with mental disorder diagnoses. How are clinicians affected by the context within which diagnostic criteria of a patient present when making diagnostic evaluations? The classification system clinicians are instructed to use is structured around a statistical approach to assessing diagnosis and does allow for the interpretation of criterial features through influences like context. The following experiment tests whether clinicians are affected by the context within which non-diagnostic information about a patient is presented. We tested clinician’s diagnostic judgments for symptoms of Conduct Disorder that were presented either in a context that should be perceived as being associated with Conduct Disorder or in a context that should not be perceived as being associated with Conduct Disorder. We found that clinicians were influenced by context, but in surprising ways. Clinicians lowered their diagnostic judgments for symptoms presented in a low associative context but did not change their estimates for high associative contexts as compared to baseline. The effect of context was also found to vary over the criterial symptoms that were presented, and this variation was associated with clinicians’ idiosyncratic ratings of the criterial symptoms. These results have interesting implications for how clinicians view their patients and for how context affects categorization more generally.