Vocal Learning part I Flashcards
Auditory learning
- auditory learning is associating a sound and action, but cannot reproduce sounds themselves
- vocal learning is not possible without auditory learning
Vocal learning
- ability to imitate and reproduce sounds
- imitation of a heard sound
- auditory feedback needed - to hear a sound you create and establish if it is the same as the intended sound
Poole et al (2005)
elephants are also vocal learners
- imitate a sound of a lorry
Vocal immitation
- ability to incorporate into one’s vocal repertoire novel sounds/ calls that are perceived in the environment
- based on ability to display auditory learning and vocal learning
- e.g. bottlenosed dolphins
- e.g. lyre birds can imitate the call of at least 20 species and other forest sounds
All vocal learners have close relatives who do not show vocal learning. Why? Jarvis (2006)
- vocal learning evolved independently from a common ancestor
- common ancestor of VL birds and VL mammals, but VL learning was lost multiple independent times in closely related bird and mammalian groups
- all birds mammals and reptiles have vocal learning to various degrees, but vocal learning birds and mammals independently amplified this trait to develop full vocal learning
Vocal learning evolved independently from a common ancestor
- would be very coincidental
Common ancestor of VL birds and VL mammals, but VL learning was lost multiple independent times in closely related bird and mammalian groups
- if this were the case, then similarities are not so remarkable, and there must eva strong natural selection to extinguish vocal learning
All birds mammals and reptiles have vocal learning to various degrees, but vocal learning birds and mammals independently amplified this trait to develop full vocal learning
- structure doesn’t always follow behaviour
- if this is the case, then non-learning species should have primordial brain structures for vocal learning
Pre-existing connectivity
- connections of anterior and posterior vocal pathways in both birds and mammals
Jarvis (2006)
What selects for vocal learning?
- individual identification
- semantic communication
- territory defence and mate attraction
- rapid adaption to sound propagation in different environments
Individual identification
- each VL learner learns own individual song
- BUT not a unique characteristic of vocal learners due to anatomical and physical differences
- due to VL, can be identified by name, so likely that identification is not a driving force
Semantic communication
- attach a label to an object
- BUT vervet monkeys can use innate calls to communicate semantically
- VL birds also use innate calls - not learned imitations
- most semantics are al innate
Territory defence and mate attraction
- VL birds use learned vocalisations to defeat/attract mates
- e.g. singing in humans can use variability
- varied frequency modulation
- mate attraction is a major driving force
Rapid adaption to sound propagation
- non VL produce their vocalisations only in specific habitats
VL change frequency of calls to allow for better communication - move around more
Predation strong selection factor for vocal learning
- nice and varied singing may also be more attractive to predators as calls stand out more than non-vocal learners (which can be habituated to)
- animals with more varied calls attract more mates, but die more because they are prey
- handicap principal
Predation strong selection factor against vocal learning
- vocal learners are top predators normally e.g. humans and whales
Bengalese finches bred in captivity for last 250 years show more variability in songs, because there are no predators - Kazuo and Okanoya (2002)
Jarvis conclusion of vocal learning
- predator pressure overcome first to see if vocalisation diversify
- after predation pressure is overcome
- what selects for vocal learning?: mating preferences, need for a rapid adaption to communicate in varied environments
- what selects against?: predation
Jarvis (2006) paper
- brain pathways in birds and humans are similar
- therefore, must be common selection pressures
- in birds and humans, there are brain regions in the cerebrums that control the acoustic structure of their vocal behaviour, but in non-vocal learners, their vocalisation centres are only in the midbrain and medulla regions
Stoeger et al (2012)
- vocal imitation has evolved in many species
- Korean formants and fundamental frequencies, put trunk inside mouth to make a vocal tract like a humans
- Koshik the elephant was able to make Korean vowel sounds
- humans were able to identify the vowel sounds
- apes cannot make human speech 0 stems from poor cortical-motor control of the larynx and the vocal tract
- Koshiks F1 and F2 matched the humans
- BUT cannot do x-ray images to see positioning of tongue
