Social influence on song acquisition was studied in 3 groups of young European starlings raised under different social conditions but with the same auditory experience of adult song. Attentional focusing on preferred partners appears the most likely explanation for differences found in song acquisition in relation to experience, sex, and song categories. Thus, pair-isolated birds learned from each other and not from broadcast live songs, females did not learn from the adult male tutors, and sharing occurred more between socially associated peers. On the contrary, single-isolated birds clearly copied the adult songs that may have been the only source of attention stimulation. Therefore, social preference appears as both a motor for song learning and a potential obstacle for acquisition from nonpreferred partners, including adults.

Vocal communication develops under social influences that can enhance attention, an important factor in memory formation and perceptual tuning. In songbirds, social conditions can delay sensitive periods of development, overcome learning inhibitions and enable exceptional learning or induce selective learning. However, we do not know how social conditions influence auditory processing in the brain. In the present study, we raised young naive starlings under different social conditions but with the same auditory experience of adult songs, and we compared the effects of these different conditions on the development of the auditory cortex analogue. Several features appeared to be influenced by the social experience, among which the proportion of auditory neuronal sites and the neuronal selectivity. Both physical and social isolation from adult models altered the development of the auditory area in parallel to alterations in vocal development. To our knowledge, this is the first evidence that social deprivation has as much influence on neuronal responsiveness as sensory deprivation.

The effect of early experience on brain development was investigated in the central auditory area of a songbird, the field L complex, which is analogous to the mammalian auditory cortex. Multi-unit recordings of auditory responses in the field L complex of adult starlings raised without any experience of adult song during development provide strong evidence of developmental plasticity both in the neuronal responses and in the functional organization of this area. Across the entire area, experimental birds, separated from adults from the age of 1 week old until they were 2 years old, had a much larger number of neurons that responded to all the stimuli than did control birds. The well-known tonotopy demonstrated in adult wild birds using the same procedure was altered. This study is the first to bring evidence of developmental plasticity in the organization of the central auditory areas in songbirds. These results are discussed in relation to other reports on effects of early experience on brain development.

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