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That is a big jump. However, one comparison the researchers glossed over was between 7-repeat and non-7-repeat children in high-sensitivity homes. Among these two groups, the children with the 7-repeat allele (the high-sensitive version of the gene) scored over 4 points lower than their peers without the offending allele. In other words, the children with the risky, “problem” allele were actually better behaved than those with the stable, less reactive allele. Four points is a less significant discrepancy than 7 points, and not even close to the 10-point, 100 percent markup seen between 7-repeat children in low- and high-sensitivity homes. But it’s not peanuts, either.
The Dutch duo were not the only researchers to document this trend. Half a dozen different studies have reached similar conclusions. Dr. Kim-Cohen, a psychology professor from Yale University, found children with the less efficient “low reactive”[25] allele of the MAO-A gene — a polymorphism responsible for doubling incidents of externalizing behaviour when found in unsupportive households — accounted for below-average externalizing behaviour when possessed by children in supportive, nurturing homes. Again, the kids with the “trouble alleles” were the ones causing less trouble.
One of the more surprising findings came from Hungarian psychologist Dr. Judit Gervai. In many ways, Gervai’s study mirrored that of Van IJzendoorn and Bakermans-Kranenburg. Both looked at the prevalence of disorganized attachment as mediated by the DRD4 7-repeat allele. Both divided mothers into groups of low and high risk — for Van IJzendoorn and Bakermans-Kranenburg, this meant separating grieving mothers based on whether or not they were still struggling to resolve their loss. Gervai, meanwhile, grouped mothers based on whether or not they engaged in “disrupted maternal communication,” meaning they appeared disoriented, excessively needy, withdrawn, or childish in their behaviour toward their children. And both found that children’s genotypes dictated whether they would be susceptible or immune to their environments.
The only difference was which gene did which.
In Van IJzendoorn and Bakermans-Kranenburg’s study, as in every other experiment we’ve reviewed that incorporated the DRD4 gene, the 7-repeat allele increased children’s reactivity (or, as Boyce would put it, their Biological Sensitivity to Context). The 7-repeat children did as well or better than non-7-repeats in stable conditions, but when put under strain by poverty, neglect, parental depression, or any other hardship, they fared particularly poorly. Gervai reached the opposite conclusion. In her study, comprising 96 middle-class Hungarian families and 42 low-income American families, the 7-repeat allele acted as a moderating variable. Those who possessed it exhibited disorganized behaviour with roughly equal frequency regardless of whether or not their mothers engaged in disrupted maternal communication. Conversely, children without the 7-repeat allele were four times more likely to exhibit signs of disorganized attachment if raised by disruptive mothers than if raised by mothers who showed no signs of disruptive behaviour. When compared to a 7-repeat child, a non-7-repeat child was twice as likely to be disorganized if each were raised by a disruptive mother, but only half as likely if raised by a non-disruptive mother. The pattern is familiar; only the variables have been reversed.
Does this mean that either Gervai or Van IJzendoorn is wrong? Not necessarily. Their studies were similar, but they weren’t identical. By focusing on slightly different environmental causes — disrupted behaviour and communication in Gervai’s study versus more subtle responses to unresolved loss in Van IJzendoorn and Bakermans-Kranenburg’s — the two studies point to different gene-by-environment interactions. For children with the 7-repeat allele, mothers’ disrupted communication and childish behaviour did not seem to matter in predicting whether or not children were disorganized in their attachment. However, more subtle psychological responses to unresolved loss did make a difference. You could conclude, then, that parenting (particularly with high-reactive children) involves more than a specific set of behaviours, but rather a certain amount of psychological preparedness that likely could benefit from external sources of support like fathers, friends, and, if necessary, counsellors. Clearly, context matters more in some cases than in others.
Boyce’s Studies
Data from dozens of papers supported Boyce’s theory, but in order for Biological Sensitivity to Context to gain real traction, he needed to do some studies of his own. One of these measured the effects of biological sensitivity and environmental stressors on children’s susceptibility to respiratory illness.
Many human studies — including almost all of those we’ve discussed so far — measure children’s environmental stressors based on the disposition, behaviour, and socioeconomic situation of their parents. As parental bonds are the closest that children experience until at least adolescence, and as parents are the people with whom children spend most of their time, the quality of a child’s home life is a logical way to gauge his or her degree of exposure to environmental stressors. But it is not the only way. With more families finding it necessary to have both parents join the work force full-time, children are spending more of their early years in childcare facilities. Though parental influence remains important, Boyce thought a daycare centre could produce an environmental impact significant enough to affect a high-sensitive child.
Boyce measured the level of environmental stress in two ways. First, he disseminated questionnaires to four childcare facilities. The questionnaires contained descriptions of 20 minor stresses a child could experience during daycare: rejection by peers, change in drop-off or pick-up routine, toilet problems, etc. The events described were not deeply traumatic, but could conceivably embarrass or upset a child. Preschool teachers completed the forms every two weeks, noting the stresses, if any, experienced by each child in her care.
Boyce’s second measure was broader. Observing each of the four participating childcare centres, Boyce’s researchers noted the teacher-to-child ratio, staff turnover rate, proportion of full- and part-time teachers, teachers’ average education level, and overall quality as measured by the venerable Clifford Early Childhood Environment Rating Scale. These five criteria were tabulated and used to place each childcare facility on a continuum of environmental stress, with two centres in the low-stress field and two considered high-stress.
Next, Boyce needed to measure each child’s Biological Sensitivity to Context. As we’ve already mentioned, this is not as simple as genotyping each child and grouping them based on which allele of a given gene they have. Without any sort of genetic calibration, Boyce needed to assess each child’s sensitivity the old-fashioned way: through experimentation and empirical evidence.
The test was carefully designed. Boyce needed a series of activities enjoyable enough to engage 3- to 5-year-old children, but challenging enough to stimulate physiological stress responses, namely an increased heart rate and heightened blood pressure. He would then measure these stress responses and, based on his findings, declare a child to be high- or low-reactive.
The trouble with performing stress tests on children is keeping results consistent. Strange environments, the presence of a person the child finds frightening or unpleasant, or a tantrum on the ride over can act as emotional and biological white noise, weakening the signal the test picks up and garbling its results. Distortion is inevitable, but a good study keeps it to a minimum. Bearing this in mind, Boyce allowed the children to see, touch, and even operate the testing equipment a week before testing, in order to make them more familiar — and hence more comfortable — with the experiment while it was being performed. He held the tests in a quiet, secluded room within the childcare facility to keep the children focused but comfortable. The examiner was a woman the children had not met before; a familiar face may have been more comforting, but also would have come with its own collection of biases, both positive and negative. Children are usually more comfortable with women than men, and the examiner had experience working with young children.
The experiment’s content was as meticulously crafted as its setting. Participants completed seven activities that provided a physical, intellectual, and emotional challenge at a level that young children would find difficult but not daunting. The tasks were as follows: an interview, using building blocks to replicate a structure built by the examiner, remembering and reciting a series of numbers, a gestalt closure task,[26] solving a dispute between hypothetical classmates, identifying an object while blindfolded, and describing an emotional event. Throughout the procedure, children wore a blood-pressure