Perceptual organization of acoustic stimuli by budgerigars (Melopsittacus undulatus): II. Vocal signals

Operant conditioning and multidimensional scaling procedures were used to study auditory perception of complex sounds in the budgerigar. In a same-different discrimination task, budgerigars learned to discriminate among natural vocal signals. Multidimensional scaling procedures were used to arrange these complex acoustic stimuli in a two-dimensional space reflecting perceptual organization. Results show that budgerigars group vocal stimuli according to functional and acoustical categories. Studies with only contact calls show that birds also make within-category discriminations. The acoustic cues in contact calls most salient to budgerigars appear to be quite complex. There is a suggestion that the sex of the signaler may also be encoded in these calls. The results from budgerigars were compared with the results from humans tested on some of the same sets of complex sounds.     

Sequential learning and rule abstraction in Bengalese finches

The Bengalese finch (Lonchura striata var. domestica) is a species of songbird. Males sing courtship songs with complex note-to-note transition rules, while females discriminate these songs when choosing their mate. The present study uses serial reaction time (RT) to examine the characteristics of the Bengalese finches’ sequential behaviours beyond song production. The birds were trained to produce the sequence with an “A–B–A” structure. After the RT to each key position was determined to be stable, we tested the acquisition of the trained sequential response by presenting novel and random three-term sequences (random test). We also examined whether they could abstract the embedded rule in the trained sequence and apply it to the novel test sequence (abstract test). Additionally, we examined rule abstraction through example training by increasing the number of examples in baseline training from 1 to 5. When considered as (gender) groups, training with 5 examples resulted in no statistically significant differences in the abstract tests, while statistically significant differences were observed in the random tests, suggesting that the male birds learned the trained sequences and transferred the abstract structure they had learned during the training trials. Individual data indicated that males, as opposed to females, were likely to learn the motor pattern of the sequence. The results are consistent with observations that males learn to produce songs with complex sequential rules, whereas females do not.     

Emotional attention modulates microsaccadic rate and direction

Involuntary microsaccades and voluntary saccades reflect human brain activities during attention and cognitive tasks. Our eye movements can also betray our emotional state. However, the effects of attention to emotion on microsaccadic activity remain unknown. The present study was conducted in healthy volunteers to investigate the effects of devoting attention to exogenous emotional stimuli on microsaccadic response, with change in pupil size as an index of sympathetic nervous system activity. Event-related responses to unpleasant images significantly inhibited the rate of microsaccade appearance and altered pupil size (Experiment 1). Additionally, microsaccadic responses to covert orienting of attention to emotional stimuli appeared significantly in the anti-direction to a target, with a fast reaction time (Experiment 2). Therefore, we concluded that attentional shifts induced by exogenous emotional stimuli can modulate microsaccadic activities. Future studies of the interaction between miniature eye movements and emotion may be beneficial in the assessment of pathophysiological responses in mental disorders.     

Sex differences in audiovisual discrimination learning by Bengalese finches (Lonchura striata var. domestica)

Both visual and auditory information are important for songbirds, especially in developmental and sexual contexts. To investigate bimodal cognition in songbirds, the authors conducted audiovisual discrimination training in Bengalese finches. The authors used two types of stimulus: an "artificial stimulus," which is a combination of simple figures and sound, and a "biological stimulus," consisting of video images of singing males along with their songs. The authors found that while both sexes predominantly used visual cues in the discrimination tasks, males tended to be more dependent on auditory information for the biological stimulus. Female responses were always dependent on the visual stimulus for both stimulus types. Only males changed their discrimination strategy according to stimulus type. Although males used both visual and auditory cues for the biological stimulus, they responded to the artificial stimulus depending only on visual information, as the females did. These findings suggest a sex difference in innate auditory sensitivity.     

Songs to syntax: the linguistics of birdsong

Unlike our primate cousins, many species of bird share with humans a capacity for vocal learning, a crucial factor in speech acquisition. There are striking behavioural, neural and genetic similarities between auditory-vocal learning in birds and human infants. Recently, the linguistic parallels between birdsong and spoken language have begun to be investigated. Although both birdsong and human language are hierarchically organized according to particular syntactic constraints, birdsong structure is best characterized as 'phonological syntax', resembling aspects of human sound structure. Crucially, birdsong lacks semantics and words. Formal language and linguistic analysis remains essential for the proper characterization of birdsong as a model system for human speech and language, and for the study of the brain and cognition evolution.     

On-line statistical segmentation of a non-speech auditory stream in neonates as demonstrated by event-related brain potentials

The ability to statistically segment a continuous auditory stream is one of the most important preparations for initiating language learning. Such ability is available to human infants at 8 months of age, as shown by a behavioral measurement. However, behavioral study alone cannot determine how early this ability is available. A recent study using measurements of event-related potential (ERP) revealed that neonates are able to detect statistical boundaries within auditory streams of speech syllables. Extending this line of research will allow us to better understand the cognitive preparation for language acquisition that is available to neonates. The aim of the present study was to examine the domain-generality of such statistical segmentation. Neonates were presented with nonlinguistic tone sequences composed of four tritone units, each consisting of three semitones extracted from one octave, for two 5-minute sessions. Only the first tone of each unit evoked a significant positivity in the frontal area during the second session, but not in the first session. This result suggests that the general ability to distinguish units in an auditory stream by statistical information is activated at birth and is probably innately prepared in humans.     

Left-side dominance for song discrimination in Bengalese finches (Lonchura striata var. domestica)

Male Bengalese finches are left-side dominant for the motor control of song in the sensorimotor nucleus (the high vocal center, or HVc) of the telencephalon. We examined whether perceptual discrimination of songs might also be lateralized in this species. Twelve male Bengalese finches were trained by operant conditioning to discriminate between a Bengalese finch song and a zebra finch song. Before training, the left HVc was lesioned in four birds and the right HVc was lesioned in four other birds. The remaining four birds were used as controls without surgery. Birds with a left HVc lesion required significantly more time to learn to discriminate between the two songs than did birds with a right HVc lesion or intact control birds. These results suggest that the left HVc is not only dominant for the motor control of song, but also for the perceptual discrimination of song. Accepted after revision: 11 September 2001 Electronic Publication     

Production of regular rhythm induced by external stimuli in rats

Animal Cognition - Rhythmic ability is important for locomotion, communication, and coordination between group members during the daily life of animals. We aimed to examine the rhythm perception...     

Perceptual chunking in the self-produced songs of Bengalese finches (Lonchura striata var. domestica)

Like humans, songbirds, including Bengalese finches, have hierarchical structures in their vocalizations. When humans perceive a sentence, processing occurs in phrase units, not words. In this study, we investigated whether songbirds also perceive their songs by chunks (clusters of song notes) rather than single song notes. We trained male Bengalese finches to react to a short noise in a Go/NoGo task. We then superimposed the noise onto recordings of their own songs and examined whether the reaction time was affected by the location of the short noise, that is, whether the noise was placed between chunks or in the middle of a chunk. The subjects’ reaction times to the noise in the middle of a chunk were significantly longer than those to the noise placed between chunks. This result was not observed, however, when the songs were played in reverse. We thus concluded that Bengalese finches perceive their songs by chunks rather than single notes.