Ontogeny of vocal learning

Question 1

Ontogeny

Answer 1

Ontogeny pertains to the developmental history of an organism within its own lifetime, as distinct from phylogeny, which refers to the evolutionary history of a species. In practice, writers on evolution often speak of species as “developing” traits or characteristics.

Question 2

Human speech learning

Answer 2

• can discriminate sounds pre-birth
• start with perception which is across all sounds (universal), then language specific, then production is language specific e.g. babbling, then leads to vocalisations

Question 3

Thorpe (1958)

Answer 3

• chaffinches bred away from conspecifics in a lab sang abnormal songs
• exposure to taped wild chaffinches made them sing songs that corresponded to taped versions
• therefore bird song is learnt in a critical period
• birds have an intact predisposition to learn the songs of their species
• birds must hear themselves to develop normal song
• neural basis of song learning are left lateralised
• in a lot of species, only male bird sing, but now more equal, and females sing too to keep males to protect offspring
• song serves three main functions:
  1. declare territory (males and females) - muting birds makes unable to defend territory
  2. mate attraction (males only) - in temperate zones, birds sing more during breeding seasons, not in the case of subtropical zones, male singing also stimulates female physiology
  3. maintain pair bond (males and females)

Question 4

Marler (1970)

Answer 4

1. sensory phase - memory or sensory acquisition, birds are quiet and listen only
2. sensorimotor stage - sub song, plastic song, crystallised song

white-crowned sparrows - plasticity around 20-50 days of age, which gradually declines with acquisition, no more new song learning after 100-150 days

Question 5

Konishsi (1965)

Answer 5

• exposure to conspecific (tutor) song e.g. tape recordings or a live tutor
• exposure to own song e.g. deafening after the sensory phase before crystallised songs leads to abnormal songs. Auditory feedback is necessary to transfer a memorised template song to motor patterns - sensorimotor stage
• deafening closed ended learner after crystallised song was produced led to no effect of song
• therefore song learning is not just innate, but it is learned as well: auditory feedback needed, exposure through tutoring needed

Question 6

Similarities between speech and song ontogeny

Answer 6

• speech and song are both complex acoustic signal
• both have a communicative function
• show clear similarities in production

Question 7

Dissimilarities between speech and song ontongeny

Answer 7

• birds can independently modulate air flow from both the lungs and the bronchi, but humans cannot
• birds can be diplophonic, and humans cannot
• human speech has pauses within the formants, filling the whole of the speech spectrum, but birds do not have formants, but a harmonic structure instead
• humans have clear similarities in perception and production
• sensorimotor theory is necessary

Question 8

Human vs. songbird perception and production

Answer 8

• human perception: precedes and guides production, and requires imitation
• songbird perception precedes production, after hatching they start to memorise songs in the memorisation phase. They do not require immediate imitation, and there is an overlap between sensory and production phases during the sensorimotor stage of learning, which is also termed the plastic song stage, which is comparable to human babbling. After the plastic song stage, leads to the crystallised stage

Question 9

Is the critical period necessary?

Answer 9

• specific phase of an organism in which there is enhanced experience
• not ethical to deprive a human of contact, so there has been little research into this.
• Genie was an unfortunate incidence, but has since been examined - she was unable to speak. Upon training could learn nouns, and was inquisitive, but could not produce grammatical sentences.

Question 10

How to assess whether a critical period is necessary?

Answer 10

1. case studies e.g. Genie. BUT lack reliability because do not know full extent of past. Doctors notes suggest that Genie had a normally birth, and although may have babbled less, all was well.
2. Brain damage can occur at different ages
3. Second language learning… do people need to learn a second language in their critical period? NO can learn anytime, but may take more cognitive effort

• little evidence to see if songbirds can learn two songs

Question 11

What closes the critical period?

Answer 11

1. hormones - evidence that the critical period ends with puberty. E.g. dyslexia and stuttering are 10times more likely to occur in boys (brain lateralisation OR social construct?)
   - in songbirds, sining begins with testosterone production. Also, song motor learning can stop or be delayed with castration
2. activity-dependence - learning itself can play a critical role in when the critical period ends. For example, those children with language learning can make greater improvements with extra learning and exposure. Same in songbirds - greater exposure means that they are more able to pick up the song
3. social factors - in humans gender roles may play a role in female advantage in language learning - community views may affect language learning. In songbirds, zebra finches raised with only their mothers showed an extended critical period, and those with male and female parents didn’t show any extended learning