Animal Models (why?) Evolution of Language

1. Animal Models (why?) • Evolution of Language understand when emerged and what human proto-language was like; examine comparative neural substrates; contributes towards better understanding of theories on mind and consciousness • Translational Research Language deficits due to neurodegenerative diseases, strokes, tumors.

2. Non-human primatesI. Efforts to get apes to produce speech are futile because their vocal apparatus is not able to produce speech (Hayes).II. SymbolsSarah (Premack), Kanzi (Savage-Rumbaugh)III. ASL (GSL)chimps *Washoe (Gardner) and “Nim” Chimpsky (Terrace)and a gorilla named Koko (Patterson).Gorillas may be a better model due to their greater social stability than chimps.

3. Questions? • Does setting make a difference? laboratory with lots of different trainers (e.g., Nim) vs living with a single trainer (e.g., Washoe) • Is the utterance truly creative or is the trainer prompting? • Does the use of symbols provide enough flexibility to enable the expression of language? • GSL criticized for not being not ASL. Yet could those modifications be interpreted as a sign of creativity? • Can language be taught or is it mimicked? (Washoe was claimed to have taught a small number of signs to a young chimp) • Language? There is little doubt about semantics although the size of the lexicon is limited when compared to humans. The evidence for the use of grammar is not as convincing.

4. Birdsong“While comparisons between birdsong and speech are not simple, there is a surprisingly large number of areas where it is fruitful to compare the two.”Doupe and Kuhl (1999) Ann Rev Neuro 22 : 567-631 I. Learning is critical to both birdsong and speech. Most animals do not need to be exposed to the communicative signals of adults in order to reproduce them.II. Vocal learning requires both perception of sound and the capacity to reproduce sound. Innate perceptual predispositions have been hypothesized. Question is how subsequent experience alters perception and production.III. Neural substrates of vocal communication in humans and birds have been compared.IV. Critical periods are evidenced in both species.

5. Acoustically share order (grammar), timing (prosody), and elementary building blocks (phonemes). Songs used communicate species and individual identity, an advertisement for mating, ownership of territory, and fitness. • However, birdsong is not analogous in the capacity of language for meaning, abstraction and flexible associations.

6. Song: several phrases in order as a unit. Some birds 100’s, others 1.

7. I. Vocal learners • Non human primates • Songbirds pas·ser·ine   (pās'ə-rīn')    adj.   Of or relating to birds of the order Passeriformes, which includes perching birds and songbirds such as the jays, blackbirds, finches, warblers, and sparrows. *NOT chickens flycatchers etc. who vocalize, but don’t learn (3) Whales (4) Bats (communication not echolocation vocalizations)

9. Vocal Learning • Need for early tutoring. Humans learn languages to which they are exposed. • Humans (e.g., Genie) and birds with normal hearing that are socially isolated, therefore not exposed to vocalizations of others, develop abnormal speech and song. • Songbirds and humans have dialects. • Can be caught as nestling instructed to tape of own species or cross-fostered to learn the song, or aspects thereof, of the fostering species. • Both songbirds and humans must be able to hear themselves in order to develop normal vocalizations. Birds deafened after sensory phase in which they have had adequate tutoring experience yet before onset of vocalization produce abnormal songs, which implies that the bird must match its own vocalization against a template. In both humans and birds that dependence lessens in adulthood. • Deafened birds produce indistinct series of sounds, not song-like; deficits in subsong similar to deficits in babbling (lacks consonants and temporal structure) in deaf infants.

10. II. Innate vs Instructive? Innate Predispositions • Nestling sparrows discriminate conspecific from heterospecific song (as measured by heart rate and begging calls). • Songbirds prefer their own species songs over alien songs as tutor models. • Isolate songs contain elements of species song, thus innate constraints on the song even in the absence of tutoring. • Innate: lack of variation across species, can learn with as few as 30 repetitions of a song, some elements develop in isolation. • Humans perceptually discriminate language phonemes; categorical perception.

11. Effects of experience • Evidence for memorization of song during critical period: 10 to 40 day old sparrows gave significantly more calls to tutored songs than novel songs. • Produce syllables of songs heard during sensory phase but not used in the final song. • Can learn songs of heterospecifics. • Some rapid learners (zebra finches) produce amorphous subsong. May be a calibration of vocal apparatus an initial mapping of motor commands and sound production a function much like babbling in humans. • During sensorimotor learning use memorized songs as template to match with own song. Ultimately elect to produce as adult a subset that may be guided by genetic biases and experience. • Human infants by 12 months no longer respond to speech contrasts that are not used in their native language. • Humans may be sensitive to prosody before birth.

12. Neurons selective for specific song in adult but broadly selective in young. • Social factors? Some species eject playback on tape, require vision, pecking, grooming.

13. III. Neural Substrates • Birdsunlike humans are sexually dimorphic, and have no cortex. • Both songbirds (HVc and RA) and humans (cortex) have high-level forebrain areas that control preexisting hierarchal pathways for vocal motor control, whereas nonlearners do not. • In both cases, stimulation evokes vocalization, lesion disrupts vocalization. • In both cases, forebrain-basal ganglia circuit important in learning. • Lateralization in songbirds • Syrinx is bilateral and controlled ipsilaterally. Far greater song deficits occurred when left tracheosyringeal nerve cut.

15. IV. Critical period stage of life cycle in an organism in which there is enhanced sensitivity to experience. • Evidence in humans (1) isolated children, (2) patients who suffer cerebral damage at different ages, and (3) studies of second language acquisition. • Closed learners: For example, sparrows have an early period of extreme plasticity (around 20-50 days) with a later gradual decline in openness with some acquisition up to 100-150 days. • Open learners: The ability to learn songs remains open or reopens seasonal in adulthood. For example, canaries. • Birds, like humans, damage to left side before vocalization onset can be reversed.