The Welfare Trait

by Adam Perkins

  The results of this study showed that by the time ten generations had elapsed, the selected mice were running on average almost twice as far as the control mice and also that the males were lazier than the females: the female-selected mice averaged 8,774 revolutions per day whereas the control females averaged 5,077 revolutions per day. The male-selected mice averaged 6,056 revolutions per day whereas the control males averaged 3,437 revolutions per day. By generation eight, the two strains of mice had already separated enough in their wheel-running behaviour that there was no overlap between them. By generation ten, there were no signs of a limit being approached and the authors concluded that increase in wheel-running could continue to respond to further selective-breeding efforts (Swallow, Carter & Garland, 1998).

  Selective-breeding studies of personality: The Russian domestication programme

  The experiments by Garland and colleagues suggest that aspects of personality in the conscientiousness domain are sensitive to selective breeding, but they tell us little about whether traits related to agreeableness can be altered by selective breeding. This is important because people with personality-related employment difficulties are not only relatively lacking in conscientiousness but also lacking in cooperativeness (Moffitt et al., 2011), which is characteristic of low scorers on agreeableness. It is therefore important to assess the effects of selective breeding on animal behaviours that plausibly relate to agreeableness.

  Arguably, the selective-breeding experiments that are most relevant to the theme of agreeableness are those done in Russia. These show that tameness in foxes can be altered by selective breeding. This experiment was begun in 1959 by Soviet scientist Dmitri Belyaev at the Institute of Cytology and Genetics of the USSR Academy of Sciences in Novosibirsk, Siberia and was directed after his death in 1985 by Lyudmila Trut (for a review of this research programme, see Trut, 1999). Belyaev was interested in how dogs became domesticated and, more specifically, wanted to test his theory that physical features seen in domestic dogs but not wild canids, such as floppy ears, curly tails and piebald fur colouration, were the by-product of selective breeding for a single attribute, namely tameness. He wanted to attempt to replicate the domestication process under scientifically controlled conditions so he obtained 100 vixens and 30 male silver foxes from fur farms and began selectively breeding the tamest individuals with each other.

  The 130 silver foxes that were the subjects of this study were already moderately tame and so were better suited to Belyaev’s purposes than wild-caught foxes, which tend to have very high mortality and very low reproduction rates in captivity. The method of selection for tameness that Belyaev’s researchers used with the fox pups produced by these founding parents was straightforward: once a month for six months (starting when the fox was one month old), a human researcher conducted a standardised tameness assessment by offering the fox a food item whilst also attempting to pet it. Since foxes reach sexual maturity at about seven months old, an overall tameness score would then be calculated for each fox after the final assessment. Based on their performance over the previous six months, foxes were then assigned to one of three classes of tameness: Class One foxes reacted in a friendly manner when petted by humans, whining and wagging their tails. Class Two foxes tolerated petting and handling by humans but without showing any emotional response. Class Three foxes fled from humans and attempted to bite when stroked or handled.

  Foxes from Class One were allowed to breed with each other, as were foxes from Class Three. This process produced two rapidly diverging strains of foxes, one highly tame and the other highly aggressive. Videos of both strains of foxes in action are available online and are worth watching to see just how enormous the behavioural differences are between the two strains of foxes: whereas the tame foxes resemble friendly puppies, jumping up, whining and trying to lick the experimenter’s hand, foxes from the aggressive strain are ferocious, growling, snapping their jaws and throwing themselves at the bars of their cages in an effort to bite the experimenter. The key point to note is that these different patterns of behaviour are the result of genetic influence and not training, because contact between humans and foxes was strictly controlled and limited to set ‘time-dosed’ periods to ensure that all foxes, whether tame or aggressive, received equal amounts of human contact.

  Within a few generations, there was no overlap in behaviour between the two fox strains so a new assessment scheme was introduced in which pups from the strain of tame foxes were scored according to the intensity of their friendliness towards the experimenter whereas pups from the aggressive breed of foxes were scored on the critical distance between the fox and the human experimenter at which aggression is first demonstrated (the greater the distance, the more aggressive the animal). In order to verify that selective breeding can change tameness in species other than the silver fox, the researchers in Russia have also successfully domesticated the American mink, the river otter and the wild grey rat using the same selective-breeding methods.

  The original aim of Belyaev’s research programme had been to test his hypothesis that the typical physical characteristics of domesticated animals were produced by selecting for tameness. This hypothesis was strongly supported as the tamed animals showed many traits now found in domestic animals such as floppy ears, curly tails and piebald fur. Such results are not relevant to the theme of this book, although two less appreciated findings are relevant. First, the Russian experimenters found that approximately 35 per cent of the variation in the selectively bred foxes’ behavioural reactions to humans was determined by genetic factors (Trut, 1999). As we will see in Chapter 7, the size of this genetic effect on the foxes’ behaviour patterns closely matches the 30–40 per cent genetic effect on human personality characteristics that has been demonstrated by twin studies, confirming across species that individual differences in personality (for that is what genetically-based behavioural patterns are) have a substantial genetic component, and so genetic studies with non-human animals such as silver foxes can be used to inform our understanding of human personality formation. Second, if the rate of personality change seen in the selective-breeding studies summarised here is extrapolated to humans, it gives us an approximate indication that welfare legislation could significantly change human personality in about 100 years by genetic change alone. In practice, this estimate is an upper bound for the power of selective breeding to change personality because mating between humans is not under the control of an experimenter.

  As a caveat, it should be noted that it is likely selective-breeding experiments of the type I have described in this chapter may over-estimate the genetic contribution to personality. We know this because of experiments in which genetically identical mouse embryos of one strain were transplanted into mothers of a second strain that is known to differ significantly in a range of behaviours connected to anxiety and learning. When tested as adults, the mice from the first strain that had been transplanted as embryos into foster mothers of the second strain (and were then raised by those foster mothers) behaved in a broadly similar way to the mice of the second strain who had been raised by their real mothers, showing that apparently genetically-based differences in behaviour between the two strains of mice were in fact a product of the combined effects of environmental differences before and after birth (for example, differences in blood chemistry when in the uterus and licking once born; Francis et al., 2003).

  However, despite these findings, we can rest assured that there is indeed a genetic contribution to behaviour, because of cross-breeding experiments. These experiments show that when animals from two opposite behavioural strains are mated, the resulting offspring display behaviour that is intermediate between that of the two parental strains. The only difference between the offspring is their mixed genetic heritage; hence, we can see that their intermediate behaviour must have a genetic origin.

  Perhaps the most famous demonstration of this phenomenon was by Dilger (1962), who cross-bred Fisher’s lovebirds (Agapornis fischeri) with p
each-faced lovebirds (Agapornis roseicollis). The lovebirds of the first strain carry nesting materials in their beaks whereas the lovebirds of the second strain carry nesting material by tucking it into the feathers of their flanks and rumps. The offspring were sterile but nevertheless attempted to breed. As part of their breeding efforts they displayed nesting behaviours and the key finding was that the strategy used to transport nesting materials was intermediate between that of the two parental strains. To start with, the hybrid birds tucked the nesting material into the feathers of their rump and flank in the manner of the peach-faced lovebirds. However, once the material was lodged in the feathers, they still gripped it with their beaks rather than letting go and so when they raised their heads, the material was pulled out again. This behaviour was repeated many times, but as the birds matured, they began to carry nesting materials in their beaks in the manner of the Fischer’s lovebirds. The tucking ritual never wholly vanished and the birds would usually turn their head to their rumps.

  This production of intermediate behaviours by cross-breeding two strains of animals is not specific to lovebirds and has since been replicated in other species, including rodents (Broadhurst, 1969; Wigger et al., 2001), deer (Endicott-Davies, Barrie & Fisher, 1996) and ducks (Faure et al., 2003). Viewed as a whole, these cross-breeding experiments allow us to accept that behavioural traits are indeed genetically influenced, since they control for differences in both the prenatal and postnatal environment.

  Conclusion

  Selective breeding for personality causes significant, genetically influenced changes in personality within as few as five generations. As a caveat, these experiments present extreme examples. It should be noted that there is more variation in human mating than in selective-breeding studies of the type cited here, so the rate of change in human personality due to welfare-related selective breeding will be slower.

  7

  Personality as a Product of Nature and Nurture

  So far in the book we have seen evidence that low scores on conscientiousness and agreeableness constitute the ‘employment-resistant’ personality profile. We have seen that the employment-resistant personality profile is over-represented amongst welfare claimants. We have also seen evidence that welfare claimants on average have more children than employed citizens, as well as evidence that welfare generosity is at least partly responsible for this reproductive difference. If we accept that personality runs in families, then a welfare state that causes claimants to have more children on average than employed citizens risks proliferating the employment-resistant personality profile.

  This is my theory of welfare-induced personality mis-development – what I label the ‘welfare trait’ theory – but it only holds true if personality is transmitted from parents to offspring. If personality did not run in families, then the children of individuals with employment-resistant personalities would be just as likely to turn out to be solid citizens as the offspring of solid citizens and vice versa.

  We saw evidence in Chapter 5 that childhood neglect appears to be the active ingredient in the environmental transmission of employment-resistant personality characteristics. We saw in Chapter 6 that selective-breeding experiments in non-human animals demonstrate that personality characteristics can be transmitted genetically from parents to offspring. However, there are concerns that psychological models created in non-human animals are too simple to be valid in humans (for example, Matthews, 2008). The purpose of this chapter is to summarise evidence that human personality characteristics are influenced by genetic as well as environmental factors.

  Circumstantial support for the idea that dysfunctional personality characteristics are transmitted from parents to children is provided by the existence of the concept of ‘problem families’. For example, Sheffield, Wright and Lunn (1971) followed up the offspring of 108 problem families and estimated that at least 250 new problem families would be created by them. I have already described in detail some of the research on problem families by Tonge and colleagues (1975). I have also mentioned that in 1981 there was an attempt to assess transmission of problem family status by tracking down and assessing the work records and other important variables of the offspring of the 66 families whose comparison they had published in 1975. The researchers (Lunn, Greathead & McLaren; W. L. Tonge had died in 1976) managed to obtain complete information on 16 sons and 18 daughters from the problem families and 13 sons and 12 daughters from the comparison families.

  Overall, this follow-up of the 1975 study revealed a pattern of results that fits the idea of transmission of personality characteristics from parents to offspring: six of the sons of the problem families were unemployed whereas none of the sons of the comparison families were unemployed. In the daughters, the pattern was similar but less extreme: ten of the problem family daughters were unemployed compared to five of the daughters of the comparison families. In keeping with the idea that the employment-resistant personality profile has an effect on social conduct in general, criminality was also far more common in the offspring of the problem group than those of the comparison group: the 19 sons of the problem families had 255 convictions between them compared to 34 convictions in the 18 sons of the comparison families. Likewise, the 26 daughters of the problem families had 58 convictions between them compared to 17 convictions in the 16 daughters of the comparison families.

  Interestingly, these differences in criminality cannot easily be explained away as being caused by greater affluence in the offspring of the comparison families because affluence levels in the two groups of offspring were similar. For example, since the participants were reluctant to disclose their earnings, the researchers assessed affluence by noting the possession of a full set of major consumer goods of the era (a car, a telephone, a colour television, a washing machine and refrigerator). Using this measure, the researchers found that five out of 29 households of the offspring of the problem families possessed the full set of consumer goods compared to six out of 25 households of the offspring of the comparison families.

  Studies of problem families such as those conducted by Tonge and colleagues are useful for providing background evidence that social and occupational maladjustment is rooted in personality. They also suggest that these maladaptive personality characteristics can be transmitted from parents to offspring by both genetic and environmental means. In order to confirm genetic involvement in human personality transmission, I shall now summarise evidence from behaviour genetic studies of personality, which compare the similarity of personality attributes of individuals with different degrees of relatedness, allowing genetic and environmental influences to be disentangled.

  Before getting further into this topic, it is worth saying a few words on common misunderstandings in genetic research. The first point to note is that humans are very similar genetically, so when we say that identical twins share 100 per cent of their DNA, we mean exactly that, as they are clones, whereas when we say that non-identical twins or siblings share on average 50 per cent of their DNA, we mean they share on average 50 per cent of the part of their DNA that varies between individual humans, which is about 0.1 per cent of our overall genome. To put this in perspective, over 90 per cent of the total human genome can be matched with corresponding regions in the mouse genome (Mouse Sequencing Consortium, 2002) and humans, bonobos and chimpanzees show even greater similarity between the part of their genomes that can be aligned (around 98 per cent; for example, Prüfer et al., 2012). These results indicate that even physically very different mammals share the vast majority of their genes. It is also important to correct a common misconception concerning the meaning of heritability. Heritability does not indicate how much influence genetic variants have on a particular attribute in a single person, it indicates how much of a role genetic variants have in creating differences in that attribute between different people (Plomin et al., 2008). Therefore, for example, we can say that the tendency for humans to have two eyes has zero heritability, even though it is 100 per cent the product of
genetic programming.

  It is also important at this stage to mention a caveat concerning genetic influences on personality, namely that we know little about which genetic variants influence personality or how they do it. For example, two decades or so ago things were more optimistic as it was thought that personality traits are shaped by a small number of influential genetic variants (known as candidate genes). A rash of studies came out supporting this approach to understanding personality (for example, Lesch et al., 1996), only for them to turn out to be unreliable as, when other scientists tried to do the same study, they found different results.

  Even attempts to find the genes for easily measured physical attributes that we know are almost completely genetically determined, such as height, have failed to identify important candidate genes. These failures have prompted a rethink, with the latest research suggesting that human quantitative traits are likely instead to be influenced by many thousands of genetic variants, each contributing a tiny amount of variance to the trait in question that is probably too small to measure even in samples of more than 100,000 people (Yang et al., 2012). If that is not complicated enough, the expression of those genes is affected by the environment through epigenetic changes, in which, for example, a process known as methylation switches genes on or off in response to environmental influences. How environmental factors connect with genes to alter their expression is not clear, but we know that they do (Spector, 2012). Nevertheless, for the purposes of the present argument, we don’t need to get bogged down in these technical issues: all we need to know is that personality has a genetic component.

  The workhorse of behaviour genetics research is the ‘twin study’, a method first suggested by Charles Darwin’s cousin, Francis Galton: ‘Twins have a special claim upon our attention; it is, that their history affords means of distinguishing between the effects of tendencies received at birth, and those that were imposed by the special circumstances of their after lives’ (Galton, 1883, p. 155). As Galton surmised, twin studies have turned out to provide a handy way of teasing apart genetic and environmental effects on a trait because the vast majority of twins are raised together, minimising shared environmental effects, yet come in two forms with different degrees of genetic relatedness: monozygotic (MZ, genetically identical twins: that is, clones) and dizygotic (DZ, genetically non-identical twins who share approximately half of their segregating genes and so are no more related than ordinary siblings). The rationale underlying twin studies is that genetic similarity should lead to phenotypic similarity, so if genes were to influence a trait, the similarity on that trait between MZ twins is expected to be higher than between DZ twins because we can be confident that MZ twins, being clones, are genetically more similar to each other than DZ twins. Conversely, if genetic factors have no effect on a trait, similarity on that trait between MZ twins should be approximately the same as between DZ twins.