Intelligence in Nature - Jeremy Narby [65]
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P. 15: SONGBIRDS LEARN TO SING
Specter (2001) writes: âCanaries live, on average, for ten years, cover a wide octave range, and sing for several reasons: to announce themselves, to claim territory, and to scare away other males when they look for a mate. (Females rarely sing.) As Charles Darwin noted, a songbirdâs early, rudimentary attempts at vocalizationâcalled subsongâhave a lot in common with the babbling of a human infant. By the time canaries are eight months old, though, they sing like adults, and their habits never vary: they sing throughout the breeding season, in the spring, and then, during the summer molting season, they shed the songs as if they were feathers. The next spring, the same birds will turn up with an entirely new repertoire.â (p. 42). Catchpole and Slater (1995) write: âLearning has been found to have a role in song development in every species of songbird studied to date. The songbirds, or oscines, are a subdivision of the passerines, comprising some 4000 of the 9000 or so species of birds known to existâ(p. 66). Skutch (1996) writes: âA large segment of avian behavior, especially its more complex forms, is perfected by learning and experience building upon the innate foundation that we call instinct. Starting with an imperfect hereditary pattern of its speciesâ song, a songbird improves his performance by listening to his elders. Birds appear to have an innate pattern of their nests; but at least the more elaborate of them, such as those of certain African weavers, are not finished without practice. Many studies have demonstrated that experience makes birds more efficient parents; pairs nesting for the first time rear fewer young than do older breeders. Although the impulse to fly in a certain direction is innate in at least some migratory birds, the competent navigation that many display by commuting annually between familiar winter and breeding territories, separated by thousands of miles, is not attained without observation, learning, and experience. These are only a few of birdsâ activities in which learning complements innate tendenciesâ (p. 121).
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P. 15: BIRDS PRACTICE SINGING IN THEIR DREAMS
Dave and Margoliash (2000) write: âSongbirds learn a correspondence between vocal-motor output and auditory feedback during development. For neurons in a motor cortex analog of adult zebra finches, we show that the timing and structure of activity elicited by the playback of song during sleep matches activity during daytime singingâ¦Our observation of neuronal replay of sensorimotor patterns during sleep is consistent with data from hippocampal studies suggesting that sleep is important for the consolidation of neuronal temporal codes for spatial memory. The fundamental prediction of our model is that birdsong learning depends on sleep or other off-line computationsâ (pp. 812, 815). On neurogenesis in the human brain, see Eriksson et al. (1998).
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P. 16: BIRD BRAINS
Pepperberg (1999) writes: âNeurobiological studies on parrots date back to the beginning of the twentieth century. Researchers at the time suggested that mammalian standards for correlations between brain structureâabsolute brain size and particularly relative cortical sizeâand intelligence might not hold for birds. Kalisher (1901), using what were clearly rather primitive techniques, found that striatal rather than cortical areas might be involved in avian intelligence. The metaphor I like to use involves looking at avian and mammalian brains as early Macintosh versus IBM-style computers. These different information-processing machines use the same wires, and when you enter the same data into their programs you get the same resultsâbut the wires are organized differently and you must use programs