Primate intelligence
- 1. Anthropology 1: Introduction to Physical Anthropology Lecture 12 – 4/5/10: Primate Intelligence SMC Spring 2010 Rebecca Frank
- 2. The main question Why are primates so smart?
- 3. The main question Why are primates so smart? Big brains are costly: metabolism alone consumes 20% of daily energy budget in humans If it weren’t good for something, selection would eliminate it… What are the benefits that lead to the evolution of large brains / intelligence in primates?
- 4. What is “Intelligence”? Intelligence not just one thing that you have more of or less of Some animals quite smart at limited skills, e.g., memory, navigation, communication Many psychologists think “intelligence” = adding together of more and more specialized skills Nutcrackers, chickadees: spatial memory Buntings: celestial navigation Bees: waggle dance
- 5. Monkeys and apes have big & complex brains Galago Rhesus Chimpanzee
- 6. Relative brain size Primates
- 7. Why are costly brains worthwhile? Our brains are expensive Make up 2% of body weight Consume 20% of metabolic energy Some animals get by with tiny brains What are the benefits of a big neocortex? Learning Problem solving
- 8. Why be flexible? Built-in behavioral strategies work in many situations When conditions are stable, little need to learn new things Experimentation can be costly Change and unpredictability may favor flexible problem solving
- 9. Flexible Problem Solving Cognitive abilities evolve to solve the adaptive problems a species faces What are the adaptive problems that seem to have been most important in the evolution of primate intelligence? Many theories have been proposed. We will discuss two main ones: Cognitive skills evolved primarily to solve ecological problems (the ecological intelligence hypothesis ) Cognitive skills evolved primarily to solve social problems (the social intelligence hypothesis )
- 10. Learning and problem solving may also be useful in other contexts too Solving complex ecological problems Processing inaccessible food items Locating and remembering food sources Navigating between food sources Solving complex social problems Keeping track of kin Keeping track of relative rank Remembering benefits given & received Manipulating rivals Managing coalitions
- 11. Testing Hypotheses Are ecological or social factors better predictors of brain (especially neocortex) size?
- 13. Ecological Intelligence Hypothesis Finding food is complicated Where is it? What is edible? When will food be available? How to get from one food site to another How to process food Two sub-hypotheses: Frugivory Extractive Foraging
- 14. Ecological Intelligence Hypothesis 1: Frugivory Exploiting short-lived, patchy food resources (fruits) may have favored special cognitive skills in primates Frugivory demands: Knowledge of fruit properties Complex spatial representations Good memory
- 15. What do primates know about fruit? Japanese macaques know Fruit grows on trees, candy doesn’t When food is available Properties of food Howler monkeys cope with toxins Many plants produce toxins as protection Howlers are picky eaters Howlers select leaves low in toxins akebi fruit
- 16. What do primates know about maps? (Spatial representations) In tropical forests, huge diversity of plant species In savanna habitats, very large ranges “ Cognitive map”: mental representation of location, availability, and quality of things in environment
- 17. Primates would like google maps… Primates seem to know What is edible Where food sites are located When food will be available How much food is available Example: Tamarins in Peru Feed on 100’s of different trees Some species fruit synchronously Tamarins visit many trees each day 70% of time move to nearest tree of same species that was not depleted Don’t revisit trees
- 18. Does frugivory correlate with large brains? A little, but not strongly
- 19. Looking at the correlation between the color vision portion of the brain and neocortex, the correlation is stronger Extent of frugivory may be related to brain size Frugivores tend to have bigger brains than folivores Barton 1998 Parvocellular cells process wavelength & detailed color information Large neocortex related to: Diurnal activity % frugivory in diet Group size
- 20. Ecological Intelligence Hypothesis 2: Extractive Foraging Exploiting foods that are difficult to process, may have favored special cognitive skills in primates Extractive foraging demands: Consumption of difficult-to-process foods Complex, multi-step activities Fine motor skills
- 21. Examples of extractive foraging Baboons dig up underground food
- 22. Examples of extractive foraging Baboons dig up underground food Capuchins extract food from Eggs Rotten wood Under bark Hard shelled nuts Spiny, sticky pods
- 23. Examples of extractive foraging Baboons dig up underground food Capuchins extract food from Eggs Rotten wood Under bark Hard shelled nuts Spiny, sticky pods Aye ayes extract insect larvae Insects burrow into wood, lay eggs Tap tree trunk to locate larvae Gnaw on branch to make pit Use 3 rd finger to extract larvae
- 24. Orangutans eat durian, neesia fruits Protected by tough or spiny shells Pungent interior Examples of extractive foraging
- 25. Mountain gorillas’ foods are abundant, but well defended Examples of extractive foraging bamboo wild celery thistles
- 26. Chimps eat many extractive foods Examples of extractive foraging Chimps fish for ants in tree nests
- 27. Chimps eat many extractive foods Examples of extractive foraging Chimps fish for termites
- 28. Chimps eat many extractive foods Examples of extractive foraging Chimps extract honey
- 29. Chimps eat many extractive foods Examples of extractive foraging West African chimps use rocks to bash open hard-shelled nuts
- 30. Does use of extractive foods correlate with large brains? Not really
- 31. Other problems with ecological intelligence hypothesis Extent of frugivory related to brain size Frugivores have bigger brains than folivores But, extractive foragers include: aye-ayes (relatively small brain) apes (relatively large brain) And, small-brained animals: cognitive maps navigate long distances forage efficiently
- 32. Social Intelligence Hypothesis Dunbar: “social intelligence” Humphrey: “social chess” Byrne & Whiten: “Machiavellian intelligence”
- 33. Primates live in relatively large groups Primates track social information Identity Group membership Kinship Dominance Alliances Primates know about own relationships Primate know about relationships of others Social challenges may favor large brains: Social Intelligence Hypothesis
- 34. Primates recognize others as individuals and keep track of group membership Know members of own group Respond aggressively to strangers Know ranges of neighboring groups Know individual members of neighboring groups Social Intelligence
- 35. Monkeys seem to know a lot about their own relationships Distinguish kin from nonkin Give submissive signals to dominant animals Recruit support from those most likely to support them Social Intelligence
- 36. Social Intelligence Monkeys know about kinship relationships of others When vervet infants scream, other females look toward mother After fights, vervets reconcile with kin of former opponents Vervets redirect aggression to kin of former opponents
- 37. Social Intelligence Triadic awareness of rank & friendship in some species Is A better friends with B than A is with me? Matters if I have a fight with B and ask A for help! Capuchins & baboons have triadic awareness of this kind A B Self ?
- 38. Social Intelligence Baboons know something about others’ rank relationships Grunt is affiliative call, scream is distress call Baboons can recognize others’ calls HRF make LRF scream, but LRF never make HRF scream Play normal sequence of calls: HRF grunt, LRF scream Play unlikely sequence of calls: LRF grunt, HRF scream Baboons react strongly to unlikely sequence
- 39. Social Intelligence Knowledge of others’ relationships useful when fights occur Able to predict who will win contest Able to predict who will support whom Able to predict who will intervene against whom Able to predict who will be effective ally
- 40. Social Intelligence Monkeys can predict what others will do Macaques and baboons often grunt when they approach others Grunts are reliable predictor of peaceful interaction Grunting facilitates friendly contact Grunting facilitates infant handling Does this mean monkeys can read other monkey’s minds?
- 41. A special kind of intelligence “ Theory of Mind” or “Mindreading” The ability to infer what others think, want, or believe And the ability to use this to understand and predict their behavior Good evidence that humans have this Other primates?
- 42. Theory of Mind In humans, ToM develops in early childhood Common experiment to test for ToM Show child M&M tube Ask what’s inside Child will guess “M&Ms” Show child tube contains pencil Adult comes into room Ask child what adult will think is in tube Up to age 3, children say “pencil” After 3-4, children say “M&Ms” Many other tests of this Autism may be a deficit specifically in theory of mind
- 43. Monkeys appear to know relatively little about what others know Vervet mothers don’t warn infant about dangerous things that they see, but infant doesn’t see Don’t do well on tasks that require taking another perspective Don’t practice deception (often) But: we might not have devised a good way of testing ToM in monkeys; this happened with apes Theory of Mind
- 44. Theory of Mind Apes may know more about what others know Recognize self in mirror Can discern others’ intent Alert others to dangers they haven’t seen Can deceive others Political maneuvering
- 45. Do Chimps have theory of mind? (Povinelli et al. 1996) Test whether seeing = knowing Chimps allowed to chose which of two humans to beg from Consistently prefer to beg from a forward-facing human
- 46. But they do not prefer… Human w/eyes open to human w/eyes closed Human w/blindfold over mouth to human w/blindfold over eyes Human w/bucket on shoulder to human w/bucket over head Human w/back turned while looking over her shoulder at the chimp to human w/back turned while looking away from chimp
- 47. But: chimps are sensitive to what others know in food competition Brian Hare and colleagues devised a test of theory of mind using food competition In chimps, dominant will always get food from subordinates Hare et al. placed food so subordinate could see it, but dominant could not – and subordinate knew dominant could not Subordinate would take food only when they knew dominant could not see it Dominant Subordinate Food
- 48. Ecological Realism Often, lab tests like Povinelli’s are poor tests Don’t look at skills being used in ecologically realistic contexts in which they evolved
- 49. Other contexts of mindreading we haven’t studied much… Cooperative hunting Stalking prey Avoiding predators
- 50. Apes’ cognitive abilities are hotly debated Some think apes have considerable knowledge of others’ minds Mind-reading Deceit Compassion & empathy Imitation Moral sentiments Others think apes have very little knowledge of others’ minds Sophisticated social learning capacities But little true understanding of others’ minds
- 51. Testing Hypotheses Are ecological or social factors better predictors of brain (especially neocortex) size?
- 52. Figure 09.07c Does social complexity correlate with large brains? Yes: better than with frugivory or extraction
- 53. Except… Social intelligence hypothesis doesn’t explain why apes are smarter than monkeys Apes all live in relatively small groups Chimp and bonobo groups rarely > 50 Gorilla groups < 20 Orangs solitary What favored evolution of enhanced cognitive abilities in apes? Apes do use lot of extractive foods Some foraging skills take long time to learn Big brain may be linked to foraging challenges Complete explanation may require multiple selective pressures
- 54. Big brains may also be linked to particular types of social challenges Generally larger neocortex ratio as clique size (within a social group) increases Simians use more “computing power” for the same clique size as prosimians Terrestrial simians more similar to apes than arboreal simians Hominoids use more “computing power” for the same clique size as simians Kudo & Dunbar 2001
- 55. Brain size may be the result of selection for flexible behavior in BOTH ecological & social domains Compare “executive brain” ratio Innovation - novel solutions to social & environmental problems Social learning - learn skills and information from others Tool use Laland & Reader 2002
- 56. So which is it? Ecological or social intelligence that drove primate brain growth? Answer isn’t clear Unlikely to be one or the other Both likely operating at the same time or in alternation over evolutionary history How does the intelligence of species in other taxa inform this question? http://www.youtube.com/watch?v=R6KvPN_Wt8I
Editor's Notes
- #7: Not 100% sure, but I think the “M” in the diamond is the average for mammals in general, the “C” is carnivores, the “U” is ungulates, etc.
- #19: The neocortex ratio (the ratio of the volume of the neocortex to the volume of the rest of the brain) is plotted against the amount of fruit in the diet
- #25: Durian fruit site: ask your produce seller to show you how to open them
- #31: The neocortex ratio (the ratio of the volume of the neocortex to the volume of the rest of the brain) is plotted against extractive versus nonextractive foraging techniques
- #48: How else might you explain this? <sub using phys cues?> no, still behave the same even if sub released first, no cues to go by> What about monkeys? <sub only go towards hidden food if dom and sub released simultaneously - using cues, not understanding of seeing = knowing>
- #50: What else - what other context would mind reading be useful? Mating competition Alliance formation
- #53: The neocortex ratio (the ratio of the volume of the neocortex to the volume of the rest of the brain) is plotted against group size. Primates who live in large groups have larger neocortex ratios than those who live in smaller groups. But what does group size mean or measure, really? What would be a better way to measure social complexity? Can a single measure really capture the suite of modular cognitive abilities that we label complex or smart?
- #54: Social hypothesis explains catarrhine intelligence, ecological hypo explains why apes are even more intelligent
- #55: Used frequency of grooming - part of same clique if groomed more often than the mean rate of grooming among all dyads Calculated mean clique size for each species - though reality clique size increases with group size, and then asympototes and declines as group size gets larger…only so many relationships are possible in a large group Humans (A) = empathy group…similar to other clique size measures for humans Humans (b) = support group - who you would ask for support in times of trouble & hair grooming networks in Kung! (average)
- #56: Executive brain = neocortex volume + striatum (internal part - planning & modulation of movement pathways, reward center, novelty-related decision making behavior) Brain stem ratio to ex brain rather than body mass - better indicator of relative growth of these executive brain parts compared to the brain part necessary to maintain the body size