Let me start by admitting that I never planned to pursue an academic career in the first place. As a result, I don’t have a typical university professor background. Whilst growing up in Switzerland, music was my main passion. I played various instruments and dreamt of touring the world as a bass guitarist. And in order to fund my music studies after completing high school, I ended up training and working on the side as a lab technician in analytical chemistry. But after having toured for a few years as a professional musician, I realized that what brought me even more alive were deep conversations with others about things that really mattered—one of the hints I saw later of my own sensitivity. Consequently, this insight led me to study psychology with the aspiration of becoming a psychotherapist.
The Path to Differential Susceptibility
Fast forward a few years and with an BSc and MSc under my belt from the University of Basel (Switzerland), I moved to London (United Kingdom), to work towards a PhD under the guidance of Prof Jay Belsky, a renowned developmental psychologist. In our first meeting, Jay introduced me to his intriguing idea of differential susceptibility. This theory suggests that children differ in how strongly their development is shaped by their environment, with more “susceptible” children being more influenced by both negative and positive environmental exposures. Although a fairly simple idea, this made a lot more intuitive sense to me than the traditional perspective taught in my psychology courses which focused exclusively on the negative impact of early adversity.
Unsurprisingly, differential susceptibility became the focus of my doctoral work. In my early work with Jay, we explored infant temperament and genes as indicators of heightened susceptibility to parenting and childcare. As the theory predicted, we found that certain temperament traits or genes were associated with an increased vulnerability to the negative effects of harsh or neglectful care but also a heightened responsiveness to warm and supportive parenting and childcare.
Along Came Sensory Processing Sensitivity
In early 2008, I reached out to Dr. Elaine Aron, with a hunch that her work on sensory processing sensitivity may have much in common with the theory of differential susceptibility. In fact, in my first email to Elaine (I just checked my archive) I wondered whether people characterized by high sensory processing sensitivity might be those who are particularly susceptible to both negative and positive environmental influences. After this initial exchange we stayed in touch, updating each other on our respective research and thoughts on sensitivity and susceptibility.
After I completed my PhD, I ran a study in a secondary school in East London evaluating an intervention aimed at promoting psychological resilience in children. I was particularly interested in finding out whether highly sensitive students would benefit more from the programme. At that time, we didn’t have a sensitivity questionnaire tailored specifically for children. So, together with Elaine and others, we developed and tested what would be known as the Highly Sensitive Child scale. And indeed, we found that sensitive children did benefit more from the intervention than less sensitive children.
This study of high sensitivity was the beginning of a fruitful collaboration with the Arons and branched out into other joint research projects, especially regarding the measurement of sensitivity in children and adults. One important finding was that people tend to fall into one of three sensitivity groups: about 30% of the population are highly sensitive, another 30% are relatively low in sensitivity, and the remaining 40% are somewhere in between. These groups are sometimes referred to as orchids, dandelions, and tulips.
The Value of an Umbrella—the Concept of Environmental Sensitivity
As my research into sensitivity advanced, it became clear to me that what the three leading theories on sensitivity (sensory processing sensitivity by Elaine and Art Aron, differential susceptibility by Jay Belsky, and biological sensitivity to context by Tom Boyce and Bruce Ellis) have in common is that all three suggest that some people are especially strongly affected by environmental influences. In order to facilitate research across these related yet different concepts, I integrated the three theories into the framework of environmental sensitivity. Importantly, environmental sensitivity doesn’t replace the three long-standing theories of sensitivity, but instead seeks to combine different aspects of the theories to provide a broader and more comprehensive perspective.
Research on sensitivity has come a long way since my early days as a PhD student, with a growing number of researchers exploring the different aspects of sensitivity today. As a result, we have much more evidence-based knowledge and this continues to grow year-on-year. In order to make this valuable body of research more easily accessible to the general public, we launched a researcher-led website in 2020: www.sensitivityresearch.com. Through this website, we provide reliable information and resources on sensitivity, share recent research findings, and offer the same self-tests online that we also use for our academic research (all for free). It is a really exciting time for all who are interested in sensitivity and there is a lot more we can learn about this important trait.
What About Me? Yes, Also Highly Sensitive
I realize that sensitivity probably always played an important role in my life even though I didn’t have the right language to describe it until I began to research it myself. Early on in the research, I thought I was probably in the middle group, a tulip, because like many men, especially those with supportive childhoods, I was not really having problems with my sensitivity. Sure I could get stressed and overstimulated, but I figured everyone did.
I see now, however, that I am more likely a healthy and fortunate orchid. As a child, my sensitivity certainly contributed to the intense connection I experienced with music. At the same time, I also deeply enjoyed analysing and thinking through complex issues. Indeed, sensitivity may account for my unusual path that includes analytical chemistry, music, psychology, and finally an academic career. It could be the secret thread that weaves all of these rather different experiences together. Looking back through the eyes of a developmental psychologist, I’m particularly grateful that my parents provided an environment that allowed me to embrace my high sensitivity and run with it wherever it would take me. According to the theory of differential susceptibility, it may be exactly my heightened sensitivity that enabled me to benefit so much from the positive aspects of my childhood environment and to acquire the creativity, confidence, and resilience that are required for the often challenging life as a university professor.
An Amazing Future for Research on HSPs
As I write, we have various projects on sensitivity under way, including one on sensitive children in primary school and a new project on HSPs and their experience of psychotherapy. There are still so many more avenues to be explored in detail, such as the genetic and neurological bases of sensitivity or the development of sensitivity across the life course. Recently, we started a monthly webinar for doctoral students from all over the world working on the topic of sensitivity, with the aim of exchanging ideas and promoting collaboration cross-culturally. Let’s see what comes next as this exciting journey continues!