COMPARATIVE PSYCHOLOGY Evolutionary explanations of human behaviour

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour EVOLUTION OF INTELLIGENCE 1.Chimpanzee 2.Cat 3.Spiny Anteater 4.Dolphin 5.Capybara 6.Squirrel Monkey 7.Manatee 8.Least Weasel 9.Beaver Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Intelligence: The ability to think flexibly. • Why did we need to become so intelligent?... [1] Foraging demands? [2] Social? [3] Language? • …Maybe all Three, we will have a look at the first Two. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Foraging demands – Finding food. • Dunbar (1992) suggests that intelligence evolved because of an increased cognitive demand on fruit-eaters to monitor a food supply that was spatially and temporally dispersed. • Fruit-eaters must remember the location of their food supply, evaluate ripeness, develop a harvesting plan and decide how they will survive in the interim. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Foraging demands – Extracting food: tool use. • Mercader et al. (2002) studied chimpanzees in a remote West African rain forest where they used stones and branches as hammers to crack open nuts when foraging. Mercader et al. claimed that many of the stone by-products of chimps nut cracking are similar to those found in early human archaeological sites in East Africa. Cont… EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Foraging demands – Extracting food: tool use. • Some of the most successful human hunter-gatherers, such as the !Kung San, use highly elaborate tools. • Some less successful groups like the Tasmanian Aborigines, used only very simple tools. • Tool use is thus an indication of intelligence in both human and non-human species. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Social theories. • Theorists such as Humphrey (1976) argue that social objects (members of the same sex) offer a completely different order of complexity from the relatively stable word of physical objects. • Individuals who best dealt with these demands to their advantage would be more successful at increasing their reproductive fitness. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Social theories – Machiavellian intelligence . • Whiten and Byrne (1988) Human intelligence may be an adaptation not just to social life, but to social problem – solving. • Individuals able to use and exploit others in their social group without causing aggression would be favoured (Byrne, 1995). This Machiavellian intelligence may appear cooperative but ultimately selfish. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Social theories – Machiavellian intelligence …cont • Forming alliances – Power in complex social groups is often determined more by having the right allies than by physical strength. • Harcourt (1992) suggests that although other animals form alliances, only catarrhine primates (e.g. baboons, apes and humans) cultivate alliances based on individual’s ability. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Social theories – Machiavellian intelligence …cont • Manipulation and deception – Among social-living animals, individual can use behavioural tactics to manipulate those who are not allies or relatives into unwitting help. • The ability to understand and plan deception appears to be restricted to great apes, although other primates seem to be able to learn such tactics by watching. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Social theories – Machiavellian intelligence …cont • Byrne (1995) Manipulative ‘tricks’ include the management of attention, in which the target’s attention is diverted towards or away from something to profit the agent of the deceit. Deception also serves to change how other animals view the agent. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Social theories – The meat-sharing hypothesis • The importance of meat – Our ancestors and modern day chimpanzees, meat was important source of saturated fat – vital for survival. • Stanford (1999) studied chimps in Tanzania’s Gombe National Park and found for a few months they starved themselves, when they did kill, the chimps went straight for the fattiest fleshy parts instead of the most nutritious. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Social theories – The meat-sharing hypothesis cont… • Meat sharing – Because the importance of meat, Stanford believes that the strategies sharing of meat paved the way for human intelligence. • Meat could be used to forge alliances and persuade females to mate… EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Social theories – The meat-sharing hypothesis cont… • …Stanford observed a number of instances supporting this ‘meat for sex hypothesis’: [1] Males chimpanzees used meat to entice females, often withholding it until mating. [2] Hunting was more prevalent in the months when females chimps were sexually receptive. [3] When begging for meat, swollen (sexual receptive) females had more success than non-swollen females. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Social theories – The meat-sharing hypothesis cont… • Stanford believed that strategic meat-sharing required considerable cognitive abilities as males had to recognize individuals and keep a ‘running score’ of debts, credits and relationships. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Comparative studies of brain size and intelligence. • Thehuman brain is a metabolically expensive organ. • Although it accounts for only 2% of total body mass, it uses about 10% of the basic metabolic rate in rhesus monkeys and about 20% in humans. • Large brains would not have evolved if it did not give humans a significant advantage. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Comparative studies of brain size and intelligence. • Brain quantity – If Intelligence were determined by brain size, the sperm whale would be at the top (see table right). EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Comparative studies of brain size and intelligence cont… • We a get better indication of the intelligence of a particular species by considering brain size relative to body size. • Jerison (1978) developed the encephalization quotient (EQ), in which the actual brain mass of a species Is divided by its ‘expected’ brain size for that body size… EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Comparative studies of brain size and intelligence cont… • …Higher quotients indicate species with larger-than-expected brains. • An EQ greater than 1 indicates a brain size greater than predicated (which could be an indicator of intelligence) and visa versa. • Using this scale, humans have the highest EQ (7) of any animal (Jerison 1978). EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • Comparative studies of brain size and intelligence cont… • The idea of an EQ is appealing but has unfortunately not been supported by research – relative brain size is not necessarily related to intelligence. EVOLUTIONARY OF INTELLIGENCE • Macphail (1982) found that rats and squirrels performed at about the same level on a learning task, but rats had an EQ of only 0.40, whereas that of squirrels was 1.10. Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • The relationship of brain size and intelligence • Head size and IQ – Sir Francis Galton (1888) found that head size and intelligence to be low and insignificant. • Wickett et al. (1994) looked at 25 separate studies, comprising over 50,000 individual samples, the majority of studies fell between 0.10 and 0.30, with a mean of just under 0.20. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • The relationship of brain size and intelligence cont… • Andreasen et al. (1993) have found (using MRI scans) significant correlations of around 0.40 between brain size and intelligence. • Haug (1987) estimated a correlation of 0.48 between brain size and number of cortical neurones… EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • The relationship of brain size and intelligence cont… • …A person with a brain size of 1400cm3 would have an average 600 million fewer cortical neurones than a person with a brain size of 1500cm3. • The difference between the low end of the normal distribution for brain size (1000cm3) and the high end (1700cm3) is a fact a staggering 4.2 billion neurones (Haug, 1987)… EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour • The relationship of brain size and intelligence cont… • …It seems reasonable to assume that such a difference would have a pronounced effect on cognitive ability. EVOLUTIONARY OF INTELLIGENCE Lana Crosbie

COMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviour Discuss the relationship between brain size and intelligence. [24 marks] Outline and evaluate the explanation of two or more mental disorders from an evolutionary perspective. [24 marks] Discuss the relationship between sexual selection and human reproductive behaviour. [24 marks] EXAM QUESTIONS Lana Crosbie

COMPARATIVE PSYCHOLOGY Evolutionary explanations of human behaviour