1. Evolution of Intelligence

2. Ecological and social factors
The relationship between brain size and intelligence
Measures of brain size

3. Ecological Selection Theory
Intelligence developed in response to environmental demands. Foraging for food, hunting, and tool use require intelligence. Obtaining food presents a cognitive challenge as the location and variations in sources of food must be remembered. Food supplies are often unpredictable and the capture of food may require complex hunting strategies.

4. RESEARCH EVIDENCE FOR ECOLOGICAL THEORY
According to the dietary hypothesis, primate species whose food supply is patchily distributed need larger brains than primate species eating food that is more widely available, due to the greater demands on their memory systems when trying to locate food. Fruits are usually more patchily distributed than leaves and so frugivores (fruit-eating primates and other species) should have larger brains than folivores (leaf-eating primates and other species), and Clutton- Brock and Harvey (1980) found this to be the case.
According to the mental maps hypothesis, species that cover a wide area in their search for food (large range size) and/or spend a large proportion of the day in foraging will have larger brains than those species that cover only a small area because they will need larger-scale mental maps. Research evidence on foraging suggests that mammals do have cognitive maps of food sources. This supports a link between intelligence and food acquisition.

5. RESEARCH EVIDENCE FOR ECOLOGICAL THEORY
According to the extractive foraging hypothesis, species that have difficulty in extracting food (e.g. they have to use tools to gain access to it) should have larger brains than those having immediate access to food. Tool use is very limited; only chimps, orang-utans, and humans routinely use tools, which can be linked to their higher intelligence. This supports the ecological theory as it suggests that intelligence is related to more complex foraging strategies.
Humans’ diet is more varied and complex than the herbivorous gorillas and orang-utans and consequently the digestive systems differ. In humans the small intestine takes up the most space, whereas in gorillas and orang- utans the colon does. This shows that the food supply exerted selective pressures on the digestive system and supports the theory that it may have done the same to the brain.

6. RESEARCH EVIDENCE AGAINST THE ECOLOGICAL THEORY
Dunbar (1998) reported across 20 primate species that there was essentially no correlation between range of foraging and the size of the neocortex and so contradicts the mental maps hypothesis. He also did not find a relationship between neocortex size and percentage of fruit in the diet and so contradicts the dietary hypothesis. He also found that there was no relationship between complexity of extractive foraging and relative neocortex size and so contradicts the extractive foraging hypothesis.
The social theory may provide a more convincing explanation of the development of human intelligence as dealing with social problems probably provides more of a cognitive challenge than finding food.

7. RESEARCH EVIDENCE AGAINST THE ECOLOGICAL THEORY
There is not a clear association between tool use and intelligence. For example, 150,000 to 300,000 years ago was a time of rapid brain growth in humans, however, tool manufacture did not show a parallel growth. Between 300,000 years ago and today human brain growth has been slight but the advancement of tools/technology has been enormous. Consequently, tool use did not exert a direct selection pressure on intelligence.
A key weakness of the foraging theory, as a basis on which to judge intelligence, is that animals with brains much smaller than humans’ successfully use cognitive maps and hunt.

8. Write 40 words on Ecological Selection Theory
Ecological Selection Theory environmental demands. Foraging for food, hunting, and tool use require intelligence. Dietary hypothesis, Mental maps, extractive foraging hypothesis and digestive systems. Against: Dunbar (1998) range of foraging and Neocortex size. Social explanation. Brain size tools and timeline. Smaller brains and foraging.

9. Social complexity
According to the social brain hypothesis, intelligence and brain size will tend to be greater in those species having complex social structures. Intelligence developed in response to the demands of group living. The social environment presents a cognitive challenge as a Theory of Mind is needed. That is, the individual must have self- awareness and an understanding that others’ intentions, viewpoint, thoughts, and emotions are different from one’s own in order to predict the behaviour of others. They will also have an evolutionary advantage if they are able to use tactical deception and detect cheating in others (Machiavellian intelligence). Social complexity includes the need for deception, the formation of coalitions, co- operative strategies, and mating strategies.

10. RESEARCH EVIDENCE FOR SOCIAL COMPLEXITY
Research on self-recognition supports the Theory of Mind. The mirror test involves applying a red mark to an animal’s forehead. Animals with a self-concept should touch this mark when they look in the mirror. Chimps and orang-utans reliably demonstrate self-recognition, whereas lower primates and non-primates do not. Theory of mind develops in humans during infancy.
Another aspect of the Theory of Mind is the ability to deceive and recognise deception in others. This is called Machiavellian intelligence and is adaptive as the individual has much to gain from being able to deceive and cheat others without raising suspicion. Observational evidence suggests that only the higher primates show tactical deception. This supports the social theory that intelligence is a result of social complexity.
Dunbar (1998) correlated both environmental and social complexity with the size of the neocortex, the area of the brain associated with higher order thinking. No relationship was found between neocortex size and environmental complexity, whereas a strong positive correlation was found between this and group size as an indicator of social complexity.

11. RESEARCH EVIDENCE FOR SOCIAL COMPLEXITY
The fossil record provides evidence that the size of the human social group has increased as we have evolved over time—from Homo sapiens co-habiting in groups of 150, to the much larger villages and towns of agricultural man. As the social group increases, so does the need for more complex interpersonal skills, supporting the theory that intelligence is required for success and survival within the group.
Schillaci (2006) found among several primate species that those having the largest relative brain sizes had monogamous mating systems. Superficially, it looks as if this finding doesn’t fit the social brain hypothesis. However, it can be argued speculatively that primate monogamy involves more complex social skills than alternative mating strategies.

12. RESEARCH EVIDENCE AGAINST SOCIAL COMPLEXITY
There is great diversity in the social systems of primates with a Theory of Mind. Orang-utans have a Theory of Mind and are thought to be intelligent but do not live in large social groups, which challenges the social complexity theory.
Social groups may exist without knowledge of others’ minds (e.g. ants) and so intelligence is not inextricably linked to social living, as the Theory of Mind and the Machiavellian hypothesis suggest.

13. RESEARCH EVIDENCE AGAINST SOCIAL COMPLEXITY
Given that many apes do live in social groups, much larger brains should be found in apes and monkeys if intelligence had a social origin. The encephalisation quotient (EQ) for primates is 2.34 and the EQ for humans is 7; the proportion of the cortex to the rest of the brain is 50% in primates and 80% in humans. Therefore we would expect primates’ brains to be two to three times bigger if group living was the main factor in the development of intelligence.
According to Byrne and Bates (2007), we shouldn’t exaggerate social skills. The enlarged neocortex improves perception, learning in social contexts, and long-term memory. Thus, these may contribute more to social complexity than social skills.

14. EVALUATION OF ECOLOGICAL AND SOCIAL THEORIES
Face validity. Both ecological theory and social theory make sense as both food acquisition and living in groups do present cognitive demands and do enhance survival and reproductive potential. However, Dunbar’s (1998) research presents strong evidence that social factors drove the evolution of intelligence. When we consider numerous primate species, several aspects of social complexity (e.g. group size; deception; mating strategy) predict brain size (especially relative neocortex size). It is thus unlikely to be a coincidence that the human species has both relatively the largest neocortex of any species and is also the most intensely social species.

15. Anthropomorphic measures of intelligence
Anthropomorphic measures of intelligence. There are great difficulties in measuring and interpreting animal intelligence. Consider the difficulty we have in creating a culturally fair test of IQ in humans to appreciate the even greater difficulty of devising a species-fair test of intelligence across animals and humans. Thus, the research evidence may lack validity as the measures of intelligence may lack accuracy, as most research relies on indirect measures of intelligence such as neocortex size.

16. Neocortex size is not synonymous with intelligence
Neocortex size is not synonymous with intelligence. Neocortex size is not a direct measure of a species’ intelligence, and so we may not be assessing intelligence very well.
Difficult to operationalise and so test foraging and social complexity. It is difficult to compare the cognitive or intellectual demands of finding food across numerous species leading very different lives in very different kinds of environment. This means the values assigned to foraging complexity may not be valid and this may have affected the correlational findings. Similarly, it is difficult to measure social complexity, group size, and mating strategy may not be valid measures of this.

17. Cause and effect. The research evidence on ecological and social factors identifies associations, which do not indicate cause and effect. Consequently, conclusions are limited to “links” rather than causes.
Direction of the effect. It cannot be established which came first: varied diet or intelligence; large social groups or intelligence. It may be that better diet and group living were consequences of the development of intelligence. In which case, what caused intelligence in the first place is not clearly established.

18. A chance mutation. Human intelligence may be the result of a chance mutation that resulted in bipedalism and so freed our hands to forage and create tools. Brain size and intelligence would be a consequence of better diet.

19. neocortex
a part of the cerebral cortex concerned with sight and hearing in mammals, regarded as the most recently evolved part of the cortex. (Back)

20. Encephalization quotient (EQ),
Encephalization quotient (EQ), or encephalization level is a measure of relative brain size defined as the ratio between actual brain mass and predicted brain mass for an animal of a given size, which is hypothesized to be a rough estimate of the intelligence or cognition of the animal. (back)

21. Brain Size Encephalisation Quotient (EQ)
Lynn – brain size has increased 3 times suggesting larger brain larger intelligence.
Willerman et al Brain volume and IQ found a positive relationship
Narr et al : Cortical thickness and IQ led to a positive relationship.
Sassaman and Zarler studied children with abnormally small brains and found that 40% were not retarded. Therefor brain size may not reflect intelligence.

22. Evaluation IQ is flawed only measures one type of intelligence.
Crows have small brains but use tools (do have a large cortex)
Cortical Neurons reflects the speed of information processing so the more the better. Although humans posses the most possibly not enough to explain intelligence.

23. Nature/nurture. Nature/nurture.
The evolutionary explanations over emphasise the role of nature and ignore nurture. It is not a question of nature or nurture, as indisputably an interactionist perspective must be taken. However, as the evolutionary explanations ignore nurture this is a key weakness.

24. Multi-perspective.
Multi-perspective. Evolutionary explanations need to be considered in combination with other explanations. Both biological and psychological factors interact in the development of intelligence and so a compromise position such as the diathesis–stress model is needed, which accounts for the influence of genetic predisposition and environmental experience.

25. Males are better!
In one study, scientists converted the SAT scores of 100, and 18-year-olds to a corresponding IQ score and found that males averaged 3.63 IQ points higher than the females [source: Jackson, Rushton]. The study, did, however, use about 10,000 more females than males, which may have affected the average, but the study's authors believe that the greater the brain tissue, the greater the ability for cognitive processing
But seriously

26. Twins and how they help
Monzygote (one egg). Genetically the same so should have same intelligence (genetic). If they have the same upbringing then hard to prove environmental or genetic factors but adoption or being brought up apart can show if one is more important than the other.
Zygotic twins: (50%) Different eggs. Brought up the same may show the environmental factors have greater influence or in fact that genetic predisposition does.

27. And finally
Evolutionary factors in the development of human intelligence, for example, ecological demands, social complexity, brain size

28. Essay
Open Book.
Discuss research into genetic and/or environmental factors associated with intelligence test performance. (8 marks + 16 marks)