Introduction to Behavioral

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anatomical and physiological systems evolved over millions of years in the crucible of 

natural selection, so did the anatomy and physiology of our brains, resulting in evolved 

psychological mechanisms (EPMs) which are essentially mental adaptations. Our 

beliefs, preferences and decision-making processes are therefore heavily shaped by our 

evolutionary past. One important implication of this, which will be explored in various 

aspects of the book, is that some of our EPMs may be obsolete, and even harmful in 

our current vastly changed social and natural environment; an often-quoted example 

is our nearly universal desire for sweet and fatty food. This may indeed have aided 

the survival of our Pleistocene ancestors, but when food is plentiful it causes obesity 

and disease. Readers who are interested in learning about evolutionary psychology in 

more detail should peruse one of the many good texts on the subject, for example that 

by Buss (1999). The more casual reader can be referred to Mean Genes, an eminently 

readable bed-side book, written by Burnham and Phelan (2001), who combine the 

disciplines of economist and biologist.

Now it should be made clear from the start that it is certainly not proposed that 

every psychological mechanism determining behavior is of genetic origin resulting 

from natural selection. This caricature of evolutionary psychology, combined with the 

misleading label of genetic determinism, is one that is unfortunately both pervasive and 

pernicious in many social sciences. There are many differences between individuals, 

groups and societies that have obviously arisen for cultural reasons, and no evolutionary 

psychologist denies this. However, what is also striking in many of the empirical studies 

that will be examined throughout this book is that there are certain universal features 

of human, and even primate, psychology which lend themselves to an evolutionary 

explanation. Such explanations will not be attempted here in terms of argument; 

suggestions will be made, but it is not appropriate to delve at length into the various 

factors that relate to whether psychological mechanisms are likely to be evolutionary 

or cultural. However, one particular area of behavior can be mentioned here as an 

example of this approach, and this is the evolution of time preference. There have 

been several recent papers in the American Economic Review on this topic (Robson 

and Szentes, 2008; Netzer, 2009; Robson and Samuelson, 2009); these have discussed 

the role of intergenerational transfers of wealth, uncertainty concerning survival rates, 

and the confl ict between short-term and long-term interests. The implications of this 

research will be considered in Chapter 8. 

Many economists and psychologists reject the theories of evolutionary psychology 

as being largely speculative. They are frequently dismissed in the social sciences 

as being ‘just-so’ stories, meaning that they are not true scientifi c theories in terms 

of proposing testable hypotheses. This view is caused by two main factors: (1) it is 

impossible by defi nition to perform experiments on the past; and (2) the past record of 

facts is highly incomplete. We will show that this dismissal is largely unjustifi ed, and that 

evolutionary psychology can indeed produce testable hypotheses, many of which have 

been confi rmed by substantial empirical evidence. Furthermore, the tendency of many 

economists to limit explanations to economic phenomena is even more unsatisfactory 

as far as ‘just-so’ stories are concerned. For example, many readers would not be 

satisfi ed with the explanations that people tend to succumb to temptation because they 

have short time horizons in decision-making, and that they make bad decisions when 

they are angry. These are also fundamentally ‘just-so’ stories because they both beg the 

questions regarding why people have short time horizons, and why we have seemingly 

harmful emotional responses like anger.

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As mentioned above, a caricature of evolutionary psychology has persisted among 

some people, relating to the claim that this new science can explain all human cognitive, 

affective, and moral capacities. However, most evolutionary psychologists would 

instead support a model of 

gene-culture coevolution. This model takes the view that 

these capacities are the product of an evolutionary dynamic involving the interaction 

of genes and culture (Cavalli-Sforza and Feldman, 1982). For most of the evolutionary 

history of living species, information has been passed on from one organism to another 

purely by genetic means. The genetic code incorporates instructions for building a 

new organism, and for making decisions based on sensory inputs. Because learning is 

costly and prone to mistakes, it is effi cient for the genome to encode all aspects of the 

environment that are constant or changing only slowly, so that decisions can be easily 

and automatically made in familiar circumstances. When environmental conditions 

vary considerably or change rapidly, organisms need to have more fl exible responses, 

which means they need to be genetically programmed to be able to learn in order 

to deal with less familiar circumstances. In relatively recent times on an evolutionary 

scale, meaning over the last seven million years or so, a different method of information 

transmission has assumed increasing importance, labeled epigenetic. This nongenetic 

mechanism for transferring intergenerational information is cultural in nature. It 

can be vertical (from parents to children), horizontal (peer to peer), oblique (older 

to younger), or can take other directions, such as from higher status to lower status. 

Dawkins (1976) has proposed that the method of transmission of cultural information 

is broadly analogous to that involved with genetic transmission, introducing the term 

‘

meme’ as a unit of information. Thus memes are replicated from one person to 

another, but imperfectly, in that they mutate, just as in a game of ‘Chinese Whispers’ 

or ‘Telephone’. Furthermore, a process of selection operates so that those memes that 

enhance the fi tness of their carriers tend to survive and be passed on more frequently 

and faithfully. Memes can be as simple as the opening four notes of Beethoven’s 5th 

symphony, or highly complex, like a religious dogma. This large variability in nature 

has led to some criticism of the gene-meme analogy, but, as Gintis (2009) has pointed 

out, modern research has shown that genes also often have ill-defi ned and overlapping 

boundaries.

The interaction of genes and culture has been of vital importance in providing the 

foundation for the rapid evolution of human traits, for example, the development of 

speech and language, and the development of morality and sophisticated social emotions 

such as jealousy, shame, pride, envy, empathy and guilt. The capacities for these traits 

are ultimately determined genetically since they depend on neurological development, 

but their survival value depends on the culture in the relevant environment. 

The importance of this concept of gene-culture coevolution is explored in more 

detail in the next chapter, since it represents a worldview that is not incorporated in all 

the different behavioral sciences. As a result, it has been claimed to be a fundamental 

component of the framework for unifying these sciences (Gintis, 2009), an approach 

sometimes referred to as 

consilience.

Cognitive neuroscience

This is another relatively new discipline, which took off in the 1980s, and it essentially 

forms the nexus of evolutionary biology and evolutionary psychology. Cognitive 

neuroscience seeks to relate neural states in the brain to mental states, and to events 

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