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11 Lieberman, P. (1984) The Biology and Evolution of Language, Harvard University Press Outstanding questions . All great apes have large air sacs attached to their larynges, and our most recent shared ancestors presumably also did. What are the acoustic and communicative functions of these air sacs in apes? Why did our hominid ancestors lose them? . Current thinking holds that, even with a human brain in control, a chimp vocal tract could not produce certain crucial speech sounds. To what degree do limitations on nonhuman vocal production result from peripheral morphology versus neural control mechanisms? . What were the crucial evolutionary innovations that allowed us to move from the highly canalized and limited vocal system of our primate ancestors to the flexible, open-ended production capabilities of modern humans? Vocal imitation, present in humans but not in other primates, appears to be one key innovation. Increased breath control, and freedom from stimulus driven control of vocalization, might be others. . What are the neural mechanisms involved in vocal learning and imitation? One approach to this problem would use subtractive brain imaging techniques to examine a vocal imitation task. Are the brain areas involved the ones that have shown recent explosive expansion in our species (such as prefrontal cortex or the cerebellum)? Are homologous areas enlarged in other vocally imitating mammals such as seals or dolphins? TICS July 2000 13/6/00 2:53 pm Page 265 Review Fitch -Evolution of speech Trends in Cognitive Sciences -Vol. 4, No. 7, July 2000

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86 Bradbury, J.W. and Vehrencamp, S.L. (1998) Principles of Animal Communication, Sinauer Consider the predicament of Barbara Ehrenreich, who is considering a vacation out West 1 : It would be nice to go on a vacation where I didn't have to worry about being ripped limb from limb by some big ursine slob...All right, I know the ecologically correct line: `They won't bother you if you don't bother them.' But who knows what bothers a bear?...So instead of communing with the majestic peaks and flower-studded meadows, I spend my hikes going over all the helpful tips for surviving an Encounter. Look them in the eye? No, that was mountain lions. Bears just hate it when you stare at them, so keep your gaze fixed dreamily on the scenery. Play dead? Let's see, that works for grizzlies but not for black bears. So do you take off the backpack, get out the wildlife guidebook, do a quick taxonomic determination and then play dead? If it is difficult to infer the intentions of other humans from their facial gestures and body language, it is even harder, Social perception from visual cues: role of the STS region Truett Allison, Aina Puce and Gregory McCarthy Social perception refers to initial stages in the processing of information that culminates in the accurate analysis of the dispositions and intentions of other individuals. Single-cell recordings in monkeys, and neurophysiological and neuroimaging studies in humans, reveal that cerebral cortex in and near the superior temporal sulcus (STS) region is an important component of this perceptual system. In monkeys and humans, the STS region is activated by movements of the eyes, mouth, hands and body, suggesting that it is involved in analysis of biological motion. However, it is also activated by static images of the face and body, suggesting that it is sensitive to implied motion and more generally to stimuli that signal the actions of another individual. Subsequent analysis of socially relevant stimuli is carried out in the amygdala and orbitofrontal cortex, which supports a three-structure model proposed by Brothers. The homology of human and monkey areas involved in social perception, and the functional interrelationships between the STS region and the ventral face area, are unresolved issues. T. Allison is at the Neuropsychology Laboratory, VA Medical Center, West Haven, CT 06516 and the Department of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA. tel: +1 203 932 5711 fax: +1 203 937 3474 e-mail: truett.allison@yale.edu A. Puce is at the Brain Sciences Institute, Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122, Australia. e-mail: puce@bsi.swin.edu.au G. McCarthy is at the Brain Imaging and Analysis Center, Box 3808, Duke University Medical Center, Durham, NC 27710, USA. e-mail: gregory. mccarthy@duke.edu Review TICS July 2000 13/6/00 2:53 pm Page 267