Brain structure, communication and cognition

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Brain structure, communication and cognition

• MSc ACSB module 2006/07
• Session 9

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Main themes

• Bigger brains ? greater ability, processing power
• Lateralisation of processing sometimes parallel
  to humans
• And categorical perception of own vocalisations
  

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Dunbar brain size, group size, gossip

• Dunbar uses NHP brain size-group size fitted
  curve to predict human group size (148) from
  human brain size
• Argues that since grooming required to maintain
  bonds in group of 150 would take too much time,
  conversation has replaced grooming as a
  bond-forming activity
• Argues that big brains allow animals /humans to
  manage bigger groups

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Group size links to vocal repertoire

• McComb Semple (2005) Biol. Letters, 1, 381-385
• Phylogenetically controlled analysis independent
  contrasts
• Big vocal repertoire ? more grooming, bigger
  group size

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Brain size - ability relationships

• Bigger animals have bigger brains anyway
  (elephant vs. mouse)
• Relate brain size to body size (Jerison)
• When body size accounted for, differences in
  brain size can be related to
• Diet
• Evolutionary relationships
• Complexity of social (group) environment

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Brain areas and abilities

• Specialised brain areas may expand to enhance
  cognition/ communication
• Szekely warblers with bigger song repertoires
  have larger song control area in brain to manage
  the bigger repertoire
• Lefebvre feeding innovation and forebrain size
• Sherry Gaulin larger hippocampus in
  food-hoarding birds and polygamous Microtus spp.

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European warbler song repertoires

• Székely et al., 1996, PRSB 263, 607-610
• Correlation r0.68 between syllable repertoire
  size and HVC residual volume
• Used phylogenetically independent contrasts

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Feeding innovations and forebrain volume

• Lefebvre et al., 1997, Anim. Behav. 53, 549-560.
• Bigger forebrains in birds that are more often
  reported to use innovative feeding techniques

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Hippocampus in food-hoarding birds
Spp. of bird that make and recover food-caches
need a better memory for location than spp. that
find food naturally. Food-hoarding spp. bigger
AVIAN HIPPO-CAMPUS than expected for body weight
(Sherry)
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Tactical deception increases with neocortex ratio
(r0.72, Byrne Corp, 2004, PRSB)
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Neocortex and mating success in NHPs

• In dull polygamous NHPs, rank (fighting ability,
  size) will determine male mating success
  dominants win and mate
• But in brighter species, non-dominants may seek
  allies and so improve their mating success
• Pawlowski et al (1998) Behaviour 135, 357-368 a
  negative correlation between neocortex size and
  mating success
• Males of spp. with a large neocortex exploit
  opportunities to undermine the dominant's
  power-based monopolisation of ovulating females,
  unlike spp. with smaller neocortex. This effect
  is independent of male cohort size.

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Social brains evolve to suit females

• Lindenfors (2005) Biol. Letters, 1, 407-410
• Difference in size of typical male and female NHP
  groups
• Often more females than males
• Different pressures males compete, females seek
  allies
• Female, not male, group size correlates with
  relative neocortex size
• So social demands on females, not males, drive
  brain evolution in NHPs as a whole

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Side bias in baboon threats

• Casperd Dunbar, 1996, Behav. Proc. 37, 57-65
• Gelada baboons use LVF gt RVF during fights,
  threats, approaches this leftward-bias enhanced
  if the level of aggression is high rather than
  low
• Suggests R hemisphere processing of emotional
  signals that are critical to success in these
  contests

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Right-hemisphere and emotion?

• Hauser (1993) Science 261, 475-477
• Rhesus monkey 4 facial expressions
• Open mouth threat Ear flap threat Fear grimace
  Copulation grimace
• Asymmetry judged from videos
• Temporal onset - which mouth corner moves first
• Fullness of development (count skin-folds eye to
  cheekbone in lip retraction)
• Humans judge expressiveness of double-right or
  double-left face portraits

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Hauser's Rhesus monkeys (2)

• Fear grimace
• 75 with asymmetric timing, LHS moves first
• Most more folds, higher mouth corner, on LHS
• Other expressions
• 50-75 of monkeys assymetric
• LHS bias also evident
• Chimaera pictures human judges find L-L image
  shows heightened fear
• Results suggest R. hemisphere dominant with
  respect to emotional expression in Rhesus monkey

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Lateralised call processing

• Hauser, 1994, PNAS, 91, 3946-3948 1998, Anim.
  Behav., 56, 41-47
• Rhesus monkeys at food dispenser in wild.
• Play call from directly behind the monkey
• Film whether turns L or R ear to identify sound
• 4 calls
• 3 monkey calls aggressive, fearful, affiliation
• Bird (Ruddy Turnstone) alarm call as control

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Results (Rhesus monkey in wild)

• Adults turn R ear (61/80 times) for monkey calls,
  L ear (13/15) for control (bird calls)
• Infants show no bias for any call
• Indicates that adults are processing own calls
  preferentially using left hemisphere, just as do
  humans with language and that restriction to L
  Hem increases over course of development

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Japanese Macaque smooth coos

• Smooth Coos are one of 7 types of Coo call in the
  monkeys repertoire
• Early and Late Smooth Coos differ in peak
  position

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Japanese monkeys (1)

• Petersen, 1978, Science 202, 324-327
• Lab. training task Early and Late Smooth Coos
  played into R or L ear at random, competing
  wide-band noise played in other ear must
  discriminate for reward using either PEAK
  POSITION or PITCH
• Showed REA (L Hem processing) in detecting early
  vs. late peak position in own calls, but not for
  pitch of calls
• Other monkey species showed no REA for these calls

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Japanese moneys (2)

• Lab learning data suggest Japanese monkeys
  process coo calls in L Hem
• Ablation of auditory cortex on L impairs
  discrimination, on R leaves it unaffected
  (Heffner)
• If L cortex removed, can re-learn but if both
  sides removed, cannot re-learn

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Implications

• Lateralisation of processing not unique to human
  language may be more widely distributed for
  efficient processing of species own
  communication signals
• What about processing of over-learned signals of
  another species, e.g., where apes/monkeys/dogs
  understand some human speech?

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References

• Ghazanfar Hauser (1999) TICS, 3 (10), 377-384
• Hauser (1997) The evolution of communication. Ch
  4 pp. 175-211 Ch 7 pp. 534-548.
• Petersen (1982) in Snowdon et al. (Eds) Primate
  communication. Ch. 8
• Barton (1997) in Whiten Byrne Machiavellian
  intelligence II. Ch. 5
• Casperd Dunbar (1996) Behav. Proc., 37, 57-65
• Byrne Corp (2004) Proc. Roy. Soc. Lond., B,
  271, 1693-1699
• Healy, de Kort Clayton (2005) TREE, 20, 17-22