Consumer behaviour is the study of the motivations surrounding a purchase of a product or service. It has been linked to the field of psychology,^[1] sociology^[2] and economics^[3] in attempts to analyse when, why, where and how people purchase in the way that they do. However, little literature has considered the link between consumption behaviour and the basics of human biology. Segmentation by biological-driven demographics such as sex and age are already popular and pervasive in marketing. As more knowledge and research is known, targeting based on consumers' biology is of growing interest and use to marketers.

As "human machines"^[4] being made up of cells controlled by a brain to influence aspects of behaviour, there must be some influence of biology on consumer behaviour and how purchase decisions are made as well. The nature versus nurture debate is at the core of how much biology influences these buying decisions, because it argues how much is can be explained through environmental and by biological factors. Neuromarketing is of interest to marketers in measuring the reaction of stimulus to marketing.^[5][6]

Lawson and Wooliscroft (2004) drew the link between human nature and the marketing concept, not explicitly biology, where they considered the contrasting views of Hobbes and Rousseau on mankind. Hobbes believed man had a self-serving nature whereas Rousseau was more forgiving towards the nature of man, suggesting them to be noble and dignified. Hobbes saw the need for a governing intermediary to control this selfish nature which provided a basis for the exchange theory, and also links to Mcgregor's Theory of X and Y, relevant to management literature. He also considered cooperation and competition, relevant to game theory as an explanation of man's motives and can be used for understanding the exercising of power in marketing channels.^[7] Pinker outlines why the nature debate has been suppressed by the nurture debate in his book The Blank Slate.^[8]

The other side of the debate is the environment can shape attitudes, learning, sensation, thinking and behaviour ^[18]

Matt Ridley suggests in Nature via Nurture (2003)^[31] the diversity of the human species is not hard-wired in the genetic code, environments are critical. Nature is not at the expense of nurture, nor is nurture at the expense of nature, there is room for both; they work together.

Genes are cogs in the machine, not gods in the sky. They are switched on and off throughout life, by external as well as internal events, their job is to absorb information from the environment at least as often as to transmit it from the past. Genes do more than carry information; they respond to experience.^[31] Susan Mineka illustrated this concept exceedingly well with her idea of prepared learning in monkeys,^[32] where she found the predisposition of genes largely affected the acquisition of fear responses to certain stimuli. Lab-reared monkeys, through vicarious experience, were easily able to acquire a fear response to a snake, but not a flower. Nature provides the instinct, and elements of nurture depend on whether the instinct is expressed.

Genes predispose individuals to determine the extent to which an individual may engage or interact with certain environments.^[31] Ridley exemplified that having ‘athletic’ genes makes one want to practice a sport, and having ‘intellectual’ genes makes one seek out intellectual activities. "The genes are the agents of nurture and are more likely to be affecting appetite more than aptitude". Genes do not make the individual intelligent, the make them more likely to enjoy learning. They encourage individuals to seek out environmental influences that will satisfy their appetites. "The environment acts as a multiplier of small genetic differences, pushing athletic children toward the sports that reward them, and pushing bright children to the books that reward them".^[31]

Whether an individual develops certain diseases or disorders is also established, to a certain degree, on the basis of nature and nurture. Genes often predispose individuals to certain disorders or diseases, while environmental factors can trigger the onset. Susceptibility of diabetes is determined by inherited differences in DNA, but environmental factors such as diet, weight, age, and physical activity seem to be triggering the onset of the disease. Genetic make-up, in addition to the environment with which the genes are exposed to, is influencing the behaviour of consumers with regard to the food choices they make. Addiction to substance abuse is partially determined by genes, which predispose individuals to have addictive personalities; however the stimuli with which an addiction develops is dependent on the environment. Addiction is persistent and compulsive, and has a significant impact upon consumer behaviour. Individuals who experience substance abuse, for example, are prone to basing their consumption primarily around the purchasing of alcohol, even at the expense of other important aspects of well-being.

The link between biology and marketing is not a new phenomenon, especially through segmentation based on the biology of sex, age, and health condition. Certain products, for example, maternity products, are targeted at certain consumers based on their biology. Maternity clothes are purposely advertised to pregnant females looking to consume based on their changing biological processes and female predisposition. The extent to which consumers are segmented and feel they are included or excluded in the segmentation in an ethical way makes this biological segmentation of growing interest for academics and marketers today. Various industries such as the insurance industry have been criticized to discriminate against consumers based on biology due to the use of genetic tests, where those with genetic diseases may have a higher premium.^[33] As scientists and marketers learn more about biology and gain greater access to consumer's biological information, ethical debates become increasingly apparent when engaging in marketing practices.

Measuring consumers' conscious and subconscious through studying their biological sensorimotor, cognitive and affective response to marketing stimuli, called neuromarketing, is of increasing interest to marketers in order to gain insight into how they consume.^[6][34] Dawkins (1989) explained that when people die they leave behind genes and memes; genes being the unit of genetic information, and memes the units of cultural information. Neuromarketing aims to examine the memory of these memes in order to manipulate them.

Through fMRI, EEG, steady state topography (SST) and magnetoencephalography (MEG) scans,^[6] marketers are able to study how consumers react, as a step towards understanding how they can influence consumption through marketing efforts. In conjunction with qualitative research methods, it can provide deep understanding into what, how and why people consume. Measuring eye tracking in e-service marketing is another example of quantitative biological methods measuring the way people consume. It analyses how consumers shop in an online environment by recording the number of mouse clicks and click maps based on eye movement.^[35]

The famous Coke vs Pepsi study ^[36] used fMRI scans to show consumers sensory taste preference to Pepsi to Coca-Cola. However, when participants were told they were drinking Coke, their brain activity also changed and they stated their preference for Coca-Cola. This shows that regardless of their biology and sensory reaction, people's consumption behaviour and preferences are influenced by the environment, in this case the perception of brands.