Rational Teenagers

The U.K. has the highest rate of teenage pregnancy in Europe. In 1999 the government resolved to change this by establishing the Teenage Pregnancy Unit (TPU), focusing “on themes of choices and taking control and responsibility around relationships and sexual behaviour” (from the TPU website). The agenda has been to educate children and young people to make appropriate choices.

The TPU has had limited success. In 1998, according to the Office for National Statistics, the conception rate for 15-17 year old girls was 46.6 per thousand. By 2005 this had dropped 11.8% to 41.1 per thousand. The drop in the actual number of conceptions was from 41089 to 39683, a 3.5% reduction. Meanwhile, the abortion rate had risen from 42.4% to 46.9%. Over the last thirty years the conception rate in this age group has generally remained above 40 per thousand. The government hopes to reduce this rate to just over 20 per thousand by 2010.

These figures, although moderately encouraging, are tempered when broken down by socio-economic status. According to a recent report from the Department for Education and Skills, the most deprived girls are four times more likely to conceive than the least deprived. This socio-economic difference is commonly found in studies around the world. Given this, it is possible that the minimal overall improvement in teenage pregnancy rates is indicative of social mobility effects, perhaps due to other government initiatives; but this remains to be demonstrated.

In 2004, Ellie Lee and colleagues from the University of Southampton revealed another socio-economic difference. According to their data, not only were poorer girls more likely to conceive, they were also much less likely to have an abortion than wealthier girls. Although pregnancy can be an accident, abortion is the result of a definite fertility decision.

The TPU appears to interpret teenage fertility decisions in light of rational choice theory, assuming that suitably presented information will afford free and informed choice, thereby reducing teenage pregnancy. The idea that humans are rational choosers has a long pedigree in the social and behavioural sciences but it has come under increased critical scrutiny since the Nobel Prize winning work of Daniel Kahneman and the recent introduction of evolutionary considerations to psychology. To be rational means to maximize one’s utility, a concept from neo-classical economics. However, the problem has always been to find a good theory of utility. Modern psychological research has shown that we have inbuilt biases that affect our notions of utility differently in different domains. The question, then, is what utilities are the TPU assuming? It is not clear.

The TPU is seeking to reduce teenage pregnancy due to its detrimental affect upon maternal health and well-being and the significant costs of social support. On well-being, the government tell us that teenage mothers are less likely to finish their education and are more likely to be poor, the infant mortality rate for babies of teenagers is 60% higher than for those born to later mothers and teenage mothers are more likely to be postnatally depressed. Although one can intuitively see links between these facts, at no point is there any discussion of why teenage girls opt to have babies in spite of these risks – and they are opting to judging by the abortion data and by a recent study from the Joseph Rowntree Foundation, which has revealed considerable planning by teenage mothers and their partners. Surely, a theory of teenage maternal utility is needed if the government wishes to successfully intervene? What is it that teenagers are seeking to maximize?

Evolutionary biologists have long known that organisms adjust their fertility decisions according to ecological conditions. For example, bird species will increase their clutch size in relatively harsh times and reduce it in times of plenty. Such decisions have been characterized as quality-quantity trade-offs whereby quantity is often favoured when times are hard, for at least some chicks will make it to adulthood. In this example the utility being maximized is that of fitness. Fitness captures the neo-Darwinian principle that genes build traits that see to it that replicas of themselves get passed on into following generations. Thus, a trait that is an adaptation is one that causes its underlying genes to increase in relative frequency in the gene pool. Adaptations include both physical and behavioural traits. So, under this description, evolution through natural selection has acted as a rational-chooser in that it has ‘designed’ organisms that maximize their fitness.

As the clutch-size example illustrates, adaptations embody decision rules: a clear behavioural dichotomy across two distinct ecological situations suggests a condition-dependent adaptation. Socio-economic status is an excellent index of ecology for it tells you about the amount of resources individuals have to maintain themselves and any offspring, and resource expenditure can be modelled under fitness-maximizing assumptions.

The different fertility decisions of low and high socio-economic status teenagers could be regarded as the outcome of a conditional fertility strategy – one best modelled as a current versus future reproduction trade-off. Many species have adaptations that enable them to discount the future to a greater or lesser extent. Animals appear to model the future on the present. If the current environment is poor this will lead to an early reproducing strategy – while one is young, and before one’s somatic capital begins to decline. If, however, there is reason to suppose a good future, accumulating resources to ensure offspring quality will lead to a late reproducing strategy – a bet is taken on the future.

Such decisions will be the outcome of adaptations that consciously assess the current situation but there are other influences too. We know that, on average, girls from low socio-economic status groups grow smaller, have an earlier menarche, and begin sexual behaviour sooner (whether or not they become teenage mothers). These facts are thought to be a consequence of maternal adaptations reducing the amount of resources in utero in response to ecological factors. Mothers reduce resources in order to have more left over for other pregnancies, and their foetuses divert scarce nutrients to build essential organs, including reproductive machinery, which switches on sooner rather than later, because sooner reproduction will maximize fitness. Consciously, according to Lee and colleagues, poorer girls know that their current situation is as good as it gets while wealthier girls know that a prolonged education and other social advantages will see to a secure family later in life, hence the clear differences in abortion decisions.

The evolutionary theory of human nature offers an explanation as to why the lengthy educational process embarked upon by the TPU has failed to have the desired impact. Teenage pregnancy represents the extreme end of a general early-reproduction strategy in poor populations and to the extent that this maximizes their fitness any material not addressing this utility will be ignored. Policies aimed at decreasing wealth inequality and increasing social mobility, as well as a sense of an improving future are far more likely to succeed in reducing this problem. One possibility would be to think of schemes that will get teenage mothers back into education as soon as possible after the birth of their child; for example, college crèches. This will improve mothers’ chances of contributing to the economy and reduce the chances of their children reproducing quite so soon. This order of economic shift will take a long time; but eight years of the TPU is two terms in government.