9. Evolution of the brain Flashcards

Question

overall what can be said about the spatial cognition hypothesis?

Answer 1

Can’t mean then that spatial awareness is what gives us our large brains. There’s nothing in spatial memory that we have that that other species do not.

Answer 2

• Byrne & Whiten (1988); Whiten & Byrne (1997) argue that manipulative devious behavior is what has driven human brain evolution (and primate) the capacity to strategically deceive and manipulate our social relationships.

Answer 3

again some chimps and monkeys seem to have this TOM and ability to manipulate- so if they are capable then doesn't explain why human brains need be so much larger because we're all social species. Also, if group living promotes Machiavellian intelligence then we would expect to see this in all social species and we do not.

Answer 4

• Byrne & Whiten (1988) Hamadryas Baboons- female observed grooming a male who was not her mate behind a male. Her male mate could see her but not the other male- she was doing this knowing that her mate did not know what she was doing and must have had some idea of what her mate could see. They argued that being able to make these manipulative and deceptive decisions is highly advantageous in navigating the social environment that you live in and getting the best out of social relationships.

Answer 5

• Silk (1999)- Bonnet macaques and other’s rank – can play the sound of a dominant individual attacking a subordinate individual and the subordinate giving way and vice versa, or can play the sound of a dominant individual attacking a subordinate. When two individuals are not around these sounds can be played. If play the first the macaques are not interested it is a sound that they are used to but if subordinate is attacking and dominant is going on then all monkeys have heads up of surprise and alertness as they know this shouldn’t happen and it is relational information that is new.

Answer 6

Hare et al. 2000 o Subordinate and dominant chimps initially in separate cages and hatches where they can see through to the central cage. o Two occluders and a piece of food is placed behind one of the occluders with either both chimps looking and then either left or dominants hatch blocked and food is moved. So in one scenario the dominant knows where the food is and in the other the subordinate (if TOM) knows that the dominant chimp has a false belief. o So test is to see if the chimps rush forward to the food- if both rush for same food subordinate will get attacked. o If subordinate knows dominant has false belief they are more likely to rush in to get the food. o May not be complete TOM but they can know what others do and do not know. o Children can pass competitive tasks at an earlier age than they can pass more complex TOM tasks. Krupenye et al., 2016 o Eye tracking when watching false belief scenarios o Suggests that there is clear evidence that some individuals amongst other great ape species are able to correctly focus their attention in a false belief paradigm

Answer 7

* Social relationships increase dramatically with group size.  three in a group then three relationships to keep track of 4=6, 5=10 and by the time you reach 6 group members there is 15 relations to keep track 10=44. * If you plot that as the group gets bigger the number of relationships increases nearly exponentially.

Answer 8

Dunbar, has focused very much on the idea that the Neocortex has evolved as a way of providing additional brain capacity to track a large number of social relationships in a close networked living species.

Answer 9

o Intelligence, sensory information, planning behaviour (speech), social manipulations, tactical deception.

Answer 10

* Neocortex ratio= Neocortex volume/ brain volume (how much is cortex versus other stuff) * Neocortex ration positively correlated with larger group size in primates (e.g. Kudo & Dunbar, 2001) the bigger the group size the larger the neocortex ratio. * There is not a huge number of data points in their research but there is a broadly positive relationship.

Answer 11

(related to group size) • Dunbar (1998) Human intelligence did not evolve Primarily as a means to solve ecological problems, but rather as a means of surviving and reproducing in large and complex social groups. Need TOM to form good relationship and engage in altruism/deception/ coalition formation Evidence to suggest that groups of 150 are particularly successful. When hominids Started living in large groups, selection favoured greater intelligence/ social skills. in a group where everyone is interdependent on everyone else for their success being able to navigate that group is really important for reproductive success. • Brain creates a Cognitive constraint -Even if environment could support more it is constrained by cognition.

Answer 12

For humans has been argued that the predicted max group size is about 150. Big brains able to support big groups.

Answer 13

Dunbar (2008) most human formed groups to tend to be around/ definitely below this 150 mark for example Chistmas card networks= 154 hunter gatherer communities= 148 doomsday book villages= 150 amongst many others

Answer 14

The more people that there are the more that you have to think about not just what you think about them but what they think about each other and how many layers of that you really need to understand what is going on in your social group.

Answer 15

there is a limit on our intentionality and how much we can understand TOM. • First order mental state=I think something • Second order= basic TOM ‘I think that you think’ • Third level intentionality= ‘You think that I think, that you think’ and so on- humans seem to struggle to do this past the fifth level in a TOM task

Answer 16

Stiller & Dunbar (2007); Powell et al., (2010)- People who can perform better on these intentionality tasks then have larger support cliques. The more people you are able to keep supportive close relationships with. These groups are very important because these are people supporting you in social environment. Can draw on these and potentially maximise reproductive potential.

Answer 17

Why is there selection for these big groups for humans? * Predation…?- one of Dunbar’s arguments- it is always better to be a bigger group because decreases risk of predation if you are one of these species who is able to have these big groups then you will have a large advantage. * Inter-group competition…?- favours bigger groups, if you’re the bigger group you are better able to compete with other members of your species. Would favour individuals who are able to maintain these strong cognitive defences against group living to be a strongly cooperative species who live together.

Answer 18

However, it has been argued that all this focus on what’s going on with the neocortex is missing out on some of the other important things about brain size across species.

Answer 19

Barton (2012) * A lot of the increase in size in the neocortex is white matter (axons/ connective tissue) the cerebellum increases more in grey matter than the neocortex- so more cell bodies. * This is very important because if we remember allometric scaling about size of body and brain- so if all you have is a lot of extra white matter- it tells you that there is more connections but maybe more long range connections- could be about the axons having to go further rather than there being more axons to start with. A lot of the increase in the neocortex might just be axons traveling further and this isn’t actually increasing reasoning/ learning ability it is just a physical increase in the size needed to travel. Whereas the cerebellum is increasing a lot in grey matter which is more cells and more processing power and therefore is quite important.

Answer 20

Cerebellum (Barton, 2012)

Answer 21

• Cerebellum increases at least as much as the neocortex * Burton 2012- “neocortex size correlates significantly with social group size…but not extractive foraging, whereas cerebellum size correlates significantly with extractive foraging but not social group size. * So potentially neocortex might be linking into these social relationship and the cerebellum is doing something too in motor sequence planning and tool use and getting more nutrition from environment.

Answer 22

o Motor coordination o Sequence processing o Planning thereof? o (Including language? Can think about planning words and syntax)

Answer 23

Dunbar (1992) suggested that there was a species specific upper limit to group size that is set by purely cognitive constraints: animals cannot maintain the cohesion and integrity of groups larger than a size fixed by the information-processing capacity of their neocortex.  the group size identified by this relationship appears to depend on the maximum number of individuals with whom an animal can maintain social relationships by personal contact

Answer 24

It is generally accepted that the cohesion of primate groups is maintained through time by social grooming (see Dunbar 1988). Social grooming is used both to establish and to service those friendships and coalitions that give primate groups their unique structure

Answer 25

As might be anticipated, the amount of time devoted to social grooming correlates well with group size, notably among the catarrhine primates (Old World monkeys and apes; Dunbar 1991).

Answer 26

Effectiveness of a coalition is directly related to the amount of time its members spend grooming each other (Dunbar, 1984)- thus larger group the more grooming time.

Answer 27

What brain size would we predict for anatomically modern humans, given our current neocortical size? I then ask whether there are any observed human group sizes that correspond to this predicted value

Answer 28

- Dunbar argues that in cases where this is not seen e.g. Australian Aboriginal tribes living in the central desert regions lack the larger clanlike groups does not necessarily refute the hypothesis. The marginal habitats occupied by these peoples seem to dictate a foraging strategy based on small, dispersed groups living in very large territories; this almost certainly creates communication problems that preclude the formation of larger social networks

Answer 29

Wynn 1988- pointed out that the evolution of large brain size within the hominid lineage does not correlate well with the archaeological record for changes in tool construction. The markedly improved tool designs of the Upper Palaeolithic can thus be better interpreted as a consequence rather than a cause of enlarged brain size

Answer 30

Suggestion is that evolution of this increased capacity arose out of the need to coordinate the large number of interpersonal relationships necessary to maintain the cohesion and stability of larger than normal groups. There is a cognitive limit to the number of individuals with whom any one person can maintain stable relationships, that this limit is a direct function of relative neocortical size

Answer 31

. argued that the need to increase group size at some point during the course of human evolution precipitated the evolution of language because a more efficient process was required for servicing these relationships than was possible with the conventional nonhuman primate bonding mechanism (i.e., social grooming).

Answer 32

DeCasien et al., 2017- Primate brain size is predicted by diet but not sociality

Answer 33

social brain hypothesis would stipulate that polyandrous primate species would have the largest brains as this would be consistent with the idea that systems that promote the most interactions and relationships between the greatest numbers of individuals might be the most cognitively demanding.

Answer 34

Some studies have supported this (Clutton-Brock, & Harvey, 1980; Shultz, & Dunbar, 2007) BUT others have found the opposite that monogamous species have the largest brains (Schillaci, 2006)- researchers finding these have argued that these species have larger brains because monogamy require greater deception and manipulation abilities for obtaining extra-pair copulations or require conflict resolution and coordination abilities for bond maintenance.

Answer 35

DeCasien et al., 2017 argue that within these studies of primate brain size evolution, species sample sizes used in analyses have been small and idiosyncratic older studies used weak statistical analysis techniques. Many include phylogeny that has become outdated.

Answer 36

DeCasien et al., 2017 argue that Difficulties associated with assigning appropriate proxies of social complexity and cognitive complexity should not be underestimated. For example, mean group size is, ‘at best, a crude proxy’ of social complexity, because larger groups may not be characterized by a corresponding increase in the number of differentiated relationships/interactions. Future studies using more sophisticated proxies may provide better support for the social brain hypothesis.

Answer 37

DeCasien et al., 2017 argue that there is too much of a focus on the neocortex rather than just brain size- Social brain hypothesis stipulates that it is total brain size not just neocortex size- Dunbar 1993- only uses neocortex The subsequent focus on the neocortex was not always based on a priori reasoning, but because neocortex analyses sometimes showed the strongest correlations with the social variables under examination. Regions outside the neocortex are also involved in complex cognitive functions (for example, cerebellum, hippocampus, striatum and studies show that overall brain size predicts global cognitive ability across non-human primates

Answer 38

Used a much larger and more representative sample of primates (>140 spp., more than tripling the sample size of previous studies) and tested whether multiple measures of sociality (mean group size, social and mating system separately) explain variation in brain size after controlling for body size, diet and phylogenetic history.

Answer 39

Contrary to the predictions of the social brain hypothesis, our results indicate that none of the sociality measures examined here explain relative brain size variation in primates, which is predicted only by diet, with frugivores having relatively larger brains than folivores.

Answer 40

Together, it seems that frugivory not only provides selective pressures on cognitive processing3–5, but compensates for the costs of a metabolically expensive brain via facilitating higher energy turnover and/or lower energy allocation to digestion.

Answer 41

1) complex social behaviors thought unique to humans have been found in other taxa that don't exhibit huge brains 2) social brain hypothesis assumes that complex social environments are more cognitively demanding than physical but no evidence for this 3) rapid expansion of hominoid cerebellum indicates that technical intelligence is equally important as social.

Answer 42

complex social behaviours (for example, coalitions, reciprocation) that were previously assumed to be unique to primates have now been found in other taxa that do not exhibit relatively large brains compared to other members of their order (such as spotted hyenas- Holekamp et al., 2004). Therefore, the premise that social complexity necessarily requires cognitive complexity may not always hold, as social living challenges might not require flexible cognitive solutions in real-time, but could be solved using simpler evolved rulesof-thumb

Answer 43

the hypothesis that complex social environments are more cognitively demanding than properties of the physical environment is partially derived from the idea that the former is more unstable than the latter and requires more processing power to navigate. This has not been demonstrated quantitatively (Bshary et al., 2011)

Answer 44

- Rapid expansion of the hominoid cerebellum suggests technical intelligence was at least as important as social intelligence in human cognitive evolution (Barton & Venditti, 2014) - Technical innovations also allowed for the increased incorporation of meat in the diet, and the advent of cooking meat and other foods

Answer 45

Together with the present study, this body of comparative work suggests that both human and non-human primate brain evolution was primarily driven by selection on increased foraging efficiency, with associated changes then perhaps providing the scaffolding for subsequent development of social skills

Answer 46

• Human brains are 6x larger than would be expected for their body size compared to the average primate, while primates as a group have sig larger brains than would be expected for mammals of the same size.

Answer 47

mosaic brain - size is not enough it should be more about structure

Answer 48

As Bouchard (2014) points out- size dominates the literature not simply because it is important in its own right, but because it is easy to measure both in live organisms and in endocasts

Answer 49

Even investigators who have focused on the correlation between brain size, cortical convolutions and cortical thickness make it clear that they believe these measures are only relevant because they reflect the structural integrity of these regions and they hypothesize that other micro-anatomical characteristics as well a neuronal circuitry will prove to be important (Luders et al. 2007)

Answer 50

This prediction has proven to be true as Jolles et al. (2011) have recently shown that functional connectivity differences between brain regions cannot be explained by gray matter density alone.

Answer 51

Future research must focus in incorporating these findings into research to fully understand what makes the human brain different.

9. Evolution of the brain Flashcards

(75 cards)