Since the 1990s, a number of different models and hypotheses have been created to explain the individual differences in human sensitivity, including Jay Belsky and Michael Pluess’s differential susceptibility theory, W. Thomas Boyce and Bruce J. Ellis’s biological sensitivity to context, and Elaine Aron’s sensory processing sensitivity. Although these theories all have their differences, the Swiss psychologist and researcher Pluess uses the umbrella term environmental sensitivity to broadly describe all of them.12 What all of these theories have in common, in comparison to the earlier temperamental theories outlined above, is that they foreground the term sensitivity, which they judge neutrally, sometimes even identifying advantages associated with this higher sensitivity. Numerous studies over the past few years have clearly shown that those people who react more sensitively to their environment, react more strongly not only to negative events but also to positive events.
This means that being highly sensitive does not, as had previously been thought, necessarily lead to an increase in psychological vulnerabilities or disadvantages, but that, on the contrary, in the right surroundings, it can actually be an advantage. Both Belsky and Pluess have been able to show that it is precisely those particularly sensitive children, whom we once called “slow to warm up,” “difficult,” or “behaviorally inhibited,” who most profit from a caring and loving relationship with their parents and consequently receive better grades and display higher social competencies than those children with “easy” temperaments.13 As Pluess said during a conversation with me, “We were able to show that children with ‘difficult’ temperaments developed better in positive, supportive surroundings than other children, precisely because their higher sensitivity meant that they reacted more strongly to positive influences.” This is what Pluess calls “differential susceptibility”—that being sensitive means you suffer more from being in a negative environment, but also that you thrive more in a positive environment.
Belsky and Pluess believe that there are biological and evolutionary reasons why differences in individuals’ sensitivities could be advantageous for a whole species when faced with uncertain conditions. If one strategy does not pay off, then the existence of the species could be assured by the alternative strategy. According to Belsky and Pluess, these differences manifest themselves in a more sensitive central nervous system and are influenced by genetics and prenatal and early postnatal factors. These individuals then react more sensitively to their environment and are thus more formed by it, a process that they can profit from.14 It could thus be the case that differences in the sensitivity of people’s nervous systems is a natural phenomenon.
Boyce and Ellis’s theory of biological sensitivity to context is also based on the idea that being more sensitive is not necessarily a disadvantage for those affected, and can indeed be an advantage. But this is only the case when these particularly sensitive children grow up in a caring, loving, and supportive environment. Then the advantages of their sensitive nature becomes clear because they profit more strongly from these positive experiences and relationships than those who are less sensitive, precisely because they are so open to and affected by external influences and thus are more influenced by them than less sensitive children.
Boyce, who teaches at the University of California, Berkeley, has been able to observe that around 15 to 20 percent of all children react particularly sensitively to their environment. He refers to these children as “orchid children” and calls all other children “dandelion children,” because, like robust dandelions, they can “grow anywhere” and have less “complicated care needs.” The orchid children, on the other hand, are more pliable and react more sensitively to their environment. Boyce discovered that orchid children react particularly strongly to negative factors in their surroundings, which he measured based on their heart rates and their levels of cortisol (which is sometimes called the stress hormone because it is released at increasingly high levels when people are stressed). These children tended to react more often with behavioral problems when faced with negative situations in the family, such as money worries, illness, or parental conflict, in comparison with the dandelion children. In later life, these orchid children were more susceptible to developing problematic behaviors and psychological problems, including drug abuse and depression. But if those same particularly sensitive and malleable children grew up in low-stress, loving, and supportive surroundings, then they were happier, more productive, and healthier than the dandelion children.15, 16
What becomes clear when we take a close look at these recent studies is that all of us differ in our environmental sensitivity. And while particularly sensitive temperaments were described in earlier studies only indirectly and often negatively—with researchers believing that being more sensitive could make people more susceptible to psychological disorders—current research suggests that high levels of sensitivity are an essential and completely neutral trait. In other words, being more sensitive can be an advantage, but it can also be a disadvantage. This is completely dependent on which experiences the highly sensitive person has in the environment in which they grow up or live. The researchers whose work we have looked at in the second half of this chapter believe that natural selection led to the development of two discrete evolutionary strategies that guaranteed the survival of our species. The advantage of the reactive or sensitive strategy could be that organisms, whether human or animal, are more vigilant, sensitive, and adaptable when faced with potential opportunities and threats in their environments and social groups. Consequently, they are better able to adapt their future behavior to these new situations.
So the next time that you as a highly sensitive man find yourself in a full, loud, and sticky train car and feel unwell or tense while your traveling companion appears to be calm, can concentrate on the newspaper despite the noise, and is even able to order a hot coffee, just remember that your sensitivity is not just a disadvantage, even if it feels so in moments like this. Because it’s likely that you’re reacting more strongly not only to the negative aspects of this situation but also to the positive: the golden field of flowers that the train is speeding past, the colors of the sunset, the trees and the shrubs, some good news in your friend’s newspaper, or a funny or loving interaction in the family sitting opposite you.
Elaine Aron’s Concept of High Sensitivity
One of the researchers investigating sensitivity during the 1990s was Elaine Aron, and she was the first to observe and identify the phenomenon of high sensitivity. Aron sees high sensitivity—or sensory processing sensitivity, to use the scientific term—as a neutral, innate temperamental trait. Highly sensitive people observe things in great detail exhaustively, think longer and more deeply before they take action, and generally react more emotionally to positive as well as negative occurrences in their surroundings. This can be observed externally as a pattern of behavior in which people are more hesitant, “slow to warm up,” or “behaviorally inhibited.” But Aron believes that the underlying cause of this observable behavior is that highly sensitive people process stimuli more deeply. Using the questionnaire that she developed during her research—the Highly Sensitive Person Scale—Aron was able to show that highly sensitive people react more strongly to both positive and negative images, that they register small visual details more quickly, and even that they benefit more strongly from therapeutic interventions than non–highly sensitive people.17, 18 Using brain imaging technology, Aron was able to show over the course of numerous studies that there were differences in the brain activity of highly sensitive and non–highly sensitive people. In highly sensitive adults, the areas of the brain connected with information processing, consciousness, empathy, and activity planning, such as the insular cortex and the inferior frontal gyrus, are all more active than in individuals who are not highly sensitive. The psychologist Bianca Acevedo summarizes the results of these studies as follows:
Collectively, the present results support the notion that sensory processing sensitivity is a trait associated with enhanced awareness and responsiveness to others’ moods, as it engages brain systems involved in sensory information processing and integration, action planning, and overall awareness. These findings highlight how the highly