Social Brain Hypothesis PDF

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Social Brain Hypothesis Previous past paper exam questions: -

Evaluate the evidence for the SBH, presenting a sceptic’s critical viewpoint of its shortcomings Critically review the SBH explaining why, on the one hand, it is widely supported, but, on the other hand, there remains critics of the hypothesis Present a compelling argument on the merits of the Social Brain Hypothesis that would convince a sceptic

The social brain hypothesis (SBH) was proposed by Dunbar (1998), it provides a framework for social intelligence testing as it emerged out of the idea that large brains evolve due to social pressures such as surviving and reproducing in large complex social groups. This has strived from primates, as a group, are characterised by having unusually large brains for their body size compared to all other vertebrates. Dunbar (1998) looked at ecological and social hypothesis and was the first to take empirical data and test it. The main focus is on the neocortex an area of the brain particularly characteristic of primates and accounts for high proportion of total brain size. Relative neocortex size correlates with a proxy for social complexity including social group size, grooming cliques (allieances) and tactical deceptions. Early explanations of having a large brain however, were around ecological factors. Animals are presented with ecological problems/challenges in their habitat that set the selection pressure for brain size. Large brains improved ability to assimilate, retain and integrate complex environmental information such as food type, food distribution, habitat type and activity timing. In comparative studies they would find a correlation between brain size and diet/oraging behaviour. These are new world monkeys and can be found in the same forests – living sympatrically. Their diet is different and when comparing brains spider monkeys have the larger brain. Spider monkeys are frugivores and howler monkeys are folivores – brains reflect cognitive abilities and underpinning the exploitation of their environment. Fruit is more patchily distributed and less predictable as they are only around certain times of the year whereas insects and leaves are everywhere. Frugivores have larger home ranges and brain size also correlates with home range sizes. However the problem with ecological hypothesis is hat is does not easily explain how smaller-brained mammals solve similar ecological problems faced by primates with their large brains. The SBH was also criticised for its social explanations for large brains with reference to neocortex ratio and social group size. The reason why apes and humans need bigger brains is because of the quality of bonded relationships we have in groups, for example relationship between mother and infant. However in a study the graph shows that apes have relatively small group sizes but still have larger brains. Another challenge of SBH is that correlational does not always equal causation. The key pressure promoting the evolution of large brain sis the social environment rather than ecological environment. The relationship between social group size and neocortex ration is in fact learning from conspecifics, social mediated learning rather than learning through trial and error. Although, the SBH was initially criticised for being conceptually vague, the SBH eventually began to receive increasing quantitative support when social explanations were researched as the reason for large brains. Studies showed that amongst primates, relative neocortex size expanded which correlates with many indices of social complexity, including social group size, number of females in

the group, grooming clique size, frequency of coalitions, male mating strategies, and the frequency of tactical deception. The SBH has caused controversy as for it to be rational it must apply to other taxa that experience the same cognitive pressures in their environment not just primates. More current research of large brains supported the idea of other taxa having a social brain as Sol’s (2009) cognitive buffer hypothesis stated that organisms that have developed a large brains are a buffer to persivations that the organism faces. This is due to species with larger brains being more socially complex, more successful reproduction and are able to be flexible in new environment and problem solving. This applies to animals with long life histories, for example primates and elephants seen in larger groups as they avoid mortality through large group size – safety in numbers, spend longer foraging – overlapping generations and have behavioural strategies (deception) The social brain hypothesis makes an assumption that having a big brain is beneficial and improves fitness. However Sol (2009) tests this assumption, are there adaptive benefits of this? Growing a large brain takes time, for long lived species such as primates and elephants have extended juvenility development and delayed maturity, Sol describes this as a cost. Large brains acquire better survival as they have the ability to respond to different situations showing innovation and can tailor their behaviour to different novel environmental stimuli. Key prediction of the cognitive buffer hypothesis (buffering from changing environmental conditions, increases survival probability and fitness through reproduction. Ability to come up with new or modified behaviours. Not only evidence in primates but large brained birds show resilience to changes, along with mammals and fish. Brains are expensive to evolve and to maintain. Dunbar (1998) claims that primates need larger brains than other species as primate ecological strategies involve more complex problem solving. This claim is plausible when applied to the behaviours of species, for example termite-extraction by chimpanzees and nut-cracking by Cebus monkeys. The social brain hypothesis refers to primates as there is evidence that primate social systems are more complex than those of other species and involve processes such as tactical deception and coalition formation, since they are socially complex this is argued the need for larger brains. Primates can manipulate other social group members by deception, they live in permeant social groups forming bonds, coalitions and alliances which are usually found in species with long life histories. Valuable social relationships and manipulative strategies in problem solving lead to increasingly larger brain size, supporting the social brain hypothesis. Primates use deception mainly when mating. Males will deceive other males in order to mate with their female. However it is argued that is this insightful, using cognitive abilities or is this just good fortune. It is questioned that maybe their behaviours appear to be intelligent but in fact they are expressing simple cognitive rules. Weaknesses of most SBH studies is that they test a single hypothesis without ensuring that the same predictions could not also arise from other equally plausible explanations. Some attempts have been made to discriminate social and ecological theories which have largely supported the SBH and have correlated social, ecological and life history to brain size. Key examples of primates being cognitively and socially intelligent intra-group relationships that leads to large brain size: -

Relationship theory Competition theory Cooperation Altruistic and agonistic behaviours – protection

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Aggression – reconciliation and policing Grooming cliques – maintaining relationships Tracking own and others relationships & recognition Permanent social bonds

Social bonds that are not evident in other taxa, explains the need for large brains in primates. Pitfalls of SBH & Large brains: -

Costs: innate behaviour, have particular way of solving a problem but environment and circumstances change, costs of being hard wired – individual trial and error learning. Ecological hypotheses receive little support Expansion of neocortex crucial component – results are not always supportive – controversy

For SBH: -

Allows behaviourally flexible responses Social cognition Long life histories – cognitive evolution Provides framework for social intelligence SBH enjoys considerable quantitative support – provides us with a testable framework Relative size of the neocortex correlates with many indices of social complexity (grooming, group size, number of females, etc.) The social brain hypothesis suggests individuals effect social solutions to solve ecological or survival problems e.g. cooperation (effecting a social solution) - the individual is affecting socio cognitive skills. It is the solution that differs.

Evidence supporting: -

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Kudo & Dunbar (2001) – grooming clique size correlates with neocortex size, requires cognition to be able to maintain relationships to keep cliques going. The larger the group size there are more individuals to cooperate with – study tested grooming capabilities of females and was concluded that they are able to maintain grooming with up to 7 individuals – cognitive limitations. Bryn & Corp (2004) - Mating success and relationships to brain size – idea of deception, using cognitive skills to undermine high ranking males shows high mating success – as neocortex increases, the correlation between mating success and dominance rank increases.

Evidence not supporting: -

Neocortex size correlating to group size – however apes have small group size but still have large brains Transitive inference – most primates have the ability to apply past experiences of relationships and apply this to new ones – cognitive intelligence. However, in a study by Cheney & Seyfarth (1985) found that vervet monkeys are vulnerable as a terrestrial monkey as they lack apparent transitive ability.

SBH on other taxa: -

Neocortex size correlates with group size in carnivores (Dunbar & Bever, 1998).

Sol (2009) cognitive buffer hypothesis:

The primary adaptive function of a large brain is to buffer individuals against environmental challenges by facilitating the construction of behavioural responses. The social brain hypothesis makes an assumption that having a big brain is beneficial and improves fitness. Sol tested this assumption – are there adaptive benefits and is this supported by the data. -

Growing a large brain takes time – density of circuitry and higher order processing Cost of time (extended development) – juvenility in primates and delayed maturity Benefit (better survival) Ability to respond to difficult situations (e.g. innovation) Tailor behaviour to different (novel) environmental stimuli

Having this big brain creates the buffer: Increases survival rates (see e.g. Shultz & Dunbar, 2006) big brained species are able to solve the challenges of a predator coming at them – solve the problem and survive and favours longer reproductive life Sol describes having a big brain as a partial compensation as there is a cost to this - cost of delayed reproduction – growing a large brain. Selection pressure on brain size, brain size is a flexible behavioural response – domain general cognition – come up with general solutions to the problems. All the time as a long lived animal there are new unusual or complex environmental conditions and therefore need to come up with new or modified behaviours. Increases survival probability and fitness – through reproduction Key prediction of cognitive buffer hypothesis: Large brains reduce mortality during adulthood (when the brain is fully functional). (Re) introduction of animals to new habitats (i.e. novel) – animals are much better survivors in these situations. Innovation rates in animals, invasive species have higher innovative rates – come up with solutions and succeed going into different/new habitats. Are larger brained animals better able to meet the demands of a new environment? -

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Birds Sol (2005) – bird species with larger brains but secrete less glucocorticoids (CORT) than birds with smaller brains. Birds use this as a hormonal stress response and use it as a buffering mechanisms against environmental stressors. However, birds with larger brains relative to body size do not have glucocorticoids therefore enhanced cognition represents an alternative to deal with new environments. Primates handle stress levels in new environments through relationships, conspecifics, cooperation and alliances. Mammals Fish

Define social brain hypothesis Explain the social complexity of primates & ways of learning Why they have large brains: social & ecological o Relationships – bonds/alliances with non kin and monogamous pair bonds o Group size o Range size o Foraging – ability to problem solve Large brains:

Benefits: long life span need a big brain as over the course of the life time there will be new challenges that need solving as environment changes over time, knowledge and plasticity ned to acquire a complex skill set in groups o Costs: innate behaviour, have particular way of solving a problem but environment and circumstances change, costs of being hard wired. Studies – for SBH o Grooming clique size – maintaining relationships between group sizes and time spent grooming (Dunbar 1993). Larger group more individuals to cooperate with o Mating success and relationships to brain size o Primate deception, Bryne & Corp (2004) found evidence of deception in different species of primates, there is a correlation between tactical deceptions and contrasts in neocortex ration therefore supporting social brain hypothesis. Studies – Against SBH o Cognitive buffer hypothesis Sol (2009) Innate behaviour o Costs for animals with slower life histories SBH evidence in other taxa o Neocortex size correlates with group size in carnivores Criticisms o

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Ecological explanations: -

Dietary – food type Mental maps – distribution of food Range size Group size...