How does it feel to be ‘highly sensitive’? If I’d heard the question without all I know now, I would have said I wouldn’t know because I wasn’t. But after the term was applied to me in 1991 by a therapist I was sent to because I had ‘overreacted’ to a medical procedure, I began to seriously study what that therapist might have meant.
What I discovered after many years of studying this innate survival strategy is that high sensitivity means, above all, thinking deeply about everything. Which makes someone like me, well, thoughtful, creative and inclined more than most to both science and spirituality. Having nearly automatic empathy – almost too much sometimes – we cry easily. We notice subtleties: birds, flowers, the lighting in a room, and if someone has rearranged the furniture.
With all that going on in a sensitive person’s brain, we are easily overstimulated. If I’m travelling and visit a museum during the day, I don’t want to go to a night club that night. Nix to all noisy restaurants. I wear noise-cancelling headsets on planes. I love giving talks about high sensitivity but am totally exhausted afterwards. The more people in the audience, the more exhausted. I am also more sensitive to pain, as that therapist noted early on, causing me to explain that to medical staff: ‘Maybe you’ve noticed with all your professional experience that some people are more sensitive… Me!’
In 2010, after years of research, I boiled all this down to the acronym DOES: ‘Depth of processing, Overarousability, Emotionally responsive and Empathic, and sensitive to Subtle stimuli’. By this definition, about 30 per cent of people have this trait of high sensitivity – and because it is a survival strategy to observe before acting, it’s a trait seen in many. We’ve all met an especially sensitive cat, dog or horse. But there are sensitive birds, fish and fruit flies too.
This common yet under-recognised trait finally gained public notice in February 1993, when the Santa Cruz Sentinel covered my research at the University of California, Santa Cruz on what I called ‘highly sensitive people’ (HSPs). After it appeared, I received dozens of letters and phone calls from people wanting to know more, so I agreed to give a lecture at the public library, in its largest auditorium. So many people showed up that the staff had to send some away. Ultimately, I wrote a book – and there turned out to be so many HSPs, it sold out and went to the top of the San Francisco Chronicle bestseller list. As an HSP myself, I never intended to write self-help books, do book signings, or give TV and radio interviews, but because other HSPs craved the information, I forged ahead. I felt like I had been walking down the street, and suddenly a parade had formed behind me.
To be clear, I did not discover a new trait. It was always there in other guises. The term ‘sensitive’ had already been applied by Carl Jung in 1913 to certain of his patients. Then, in the 1950s, the New York child psychiatrists Alexander Thomas and Stella Chess rebelled against the standard Freudian view of childhood as influenced primarily by early experience and psychosexual urges. Instead, they stated the obvious: from birth, children are different from each other. And those differences were worth studying. They named nine traits they had observed in infants, including low ‘sensory threshold’, evocative of the high sensitivity I came to study myself. Later, they grouped children into three broad types: easy, difficult, and ‘slow to warm up’. The last fits the trait of sensitivity fairly well.
A closer fit came from the Harvard psychologist Jerome Kagan who, beginning in the 1980s, studied what he called ‘inhibited’ versus ‘uninhibited’ children, classifying them according to their reaction in a standard laboratory setting with various strange objects and activities. Inhibited children hung back and seemed afraid, part of what would be the classic problem of trying to understand what was going on ‘under the hood’ for those who are slower to enter into unfamiliar activities.
At the time, I wondered whether sensitivity and introversion might be the same
Yet I saw a problem with his terminology – who wants to have a child labelled ‘inhibited’? After that therapist had called me ‘highly sensitive’, I wondered if that might be a better way to describe the trait. I found a few scattered uses of the term. It had been applied to gifted persons, to parents who are especially attuned to their children, and in clinical descriptions that seemed to assume we all know what ‘sensitive’ means.
In the beginning, my approach to researching the trait was qualitative – interviewing people who, upon reading the description on a flyer I distributed, recognised themselves as either highly sensitive or very introverted. At the time, I wondered whether sensitivity and introversion might be the same because psychologists saw introversion as centred more around sensitivity to stimuli and to overarousal than to sociability.
I interviewed 39 people, equal numbers of the two biological sexes and from each decade of life, starting with college-age students. I also aimed for a variety of occupations. When I was done, I found that a third of the highly sensitive people I had interviewed were extraverts; depending on the measure you use, that might be closer to 40 per cent.
I then wanted to create a measure of the trait. I came up with about 60 possible questionnaire items, based on my interviews, and my husband Arthur Aron, whose specialty is statistics, used these to create a 27-item measure with good statistical reliability and validity. We then tested it using thousands of students in introductory psychology classes around the US.
Our first article, published in 1997, covered seven studies, including a random-digit-dialling survey for greater diversity. Not only did we separate the trait from introversion but also from ‘neuroticism’ – one of the Big Five personality traits associated with irritability, anxiety and a predisposition to negative emotion overall. Finally, we named the trait in question ‘sensory processing sensitivity’, because there was something different in how highly sensitive people processed information.
The final paper, with its 27-item measure, was published in one of the leading journals in the field of personality, and has now been cited more than 1,600 times.
Among the questions we asked to identify the highly sensitive person, we included:
- Are you easily overwhelmed by strong sensory input?
- Do you seem to be aware of subtleties in your environment?
- Do other people’s moods affect you?
- Do you tend to be more sensitive to pain?
- Do you have a rich, complex inner life?
- Are you made uncomfortable by loud noises?
- Are you deeply moved by the arts or music?
- Does your nervous system sometimes feel so frazzled that you just have to go off by yourself?
And 19 more like these. You get the idea.
At the same time, other researchers were also noticing HSPs. In fact, two other, prominent views of sensitivity, based on research mostly with children, were formulated over the same years that we did our initial work on adults. Jay Belsky and Michael Pluess developed what they called the differential susceptibility theory (DST), suggesting that the process of natural selection has produced individuals who differ fundamentally in their sensitivity to rearing influences, with some being generally more malleable (ie, susceptible) and others more fixed in their development, all due to predominately genetic factors. Importantly, studies based on DST find that susceptible individuals are not only more affected by adversity but also benefit more from positive experiences.
The paediatrician W Thomas Boyce happened upon high sensitivity and differential susceptibility through a study of respiratory illness in children, finding that those with more ‘reactive’ nervous systems were more likely than others to miss school due to sickness if they were living or going to school in a stressful environment, but less likely in a positive environment. Boyce and his colleague Bruce Ellis went on to offer their own evolutionary theory, biological sensitivity to context, suggesting that all individuals differ in their sensitivity to their very early environment. Infants, sensing either a very stressful or a very optimal environment, develop a heightened physiological reactivity, keeping them very attuned to their environment. Those in average environments do not develop this high sensitivity, the researchers found.
No matter the culture, the brains of highly sensitive people appear to be better at seeing things ‘as they really are’
Art and I, meanwhile, continued our own research, often with collaborators. Using functional magnetic resonance imagining (fMRI, an MRI while one does a task), we found that those scoring higher on the HSP scale took more care than others (and used more areas of the brain) when having to make fine distinctions between stimuli – for instance, comparing photographs of two almost-identical scenes.
One of my favourite perceptual studies compared those raised in collectivist cultures (eg, China) and in independent cultures (eg, the US). People from these two types of cultures naturally see things differently, even on simple perceptual tasks involving identifying differences in the larger context (easy for collectivist) and seeing slight differences in details (easy for independents). ‘Easy’ can be observed in an fMRI by how much the brain is working during the task. Normally, one’s culture leads to differences depending on the task. However, no matter the culture, the brains of highly sensitive people showed no difference – their perceptual judgments were not affected. They appear to be better at seeing things ‘as they really are’.
Another fMRI study found that those high on the HSP scale were higher in empathy. Highly sensitive people had a greater reaction to photos of both happy and sad faces, compared with neutral faces, and to photos of a spouse’s happy or sad facial expressions, compared with strangers with the same expressions. Of special note: increased activation could be found not in brain regions associated with specific or pure emotion but rather in sensorimotor areas with mirror neurons, associated with empathy (for instance, the ventral medial prefrontal cortex and the precuneus).
Similarly, in several studies, highly sensitive adults exposed to video clips selected to induce positive, negative and mixed emotions reported stronger emotions and a broader range of emotions compared with those with lower sensitivity. What’s more, the highly sensitive had faster responses to emotional faces but not to neutral ones.
This makes sense in light of the most important aspect of sensory processing sensitivity, underlying all the others – depth of processing. It may surprise you that emotions, far from interfering with our processing of information, often facilitate it. If you want to remember a phone number, you have to emotionally care about having that number when you need it. If you want to learn a language, by going to the country where it is spoken you will be constantly motivated to remember how to say something. In short, if you want to process information more thoroughly, it helps to have feelings about it – and this power is built into HSPs. Everyone remembers negative experiences but, to take full advantage of a situation, one needs to remember positive experiences too. Several studies have found that HSPs are more attuned to the positive than others. Finally, a variety of studies associated the resting-state brain patterns and neural connectivity of the highly sensitive person with greater attentional control, superior memory consolidation, and the ability to think slowly and carefully, aiding decision-making and planning.
This innate survival strategy involves noticing and adapting to details, especially in the social environment
An important breakthrough, to me, was the computer simulation work by Max Wolf and colleagues in 2008. The team sought to identify the conditions under which a species would develop a trait that looks behaviourally like shyness, but which is actually something more like sensitivity. He demonstrated that a strategy of making greater use of information about environmental stimuli when faced with a decision would develop as a trait when there are enough payoffs in a species’ environment for gathering that information. For example, if food patches vary in nutritional value, noticing these differences is an advantage. If food patches differ very little, or the energy required for accessing those patches is high, then there is little payoff for noticing these differences, and the strategy will not be passed on.
Further, Wolf’s team found, the trait of high sensitivity is always seen only in a significant minority because there is no advantage to any individual if all of them notice and consider details about food patches (or anything else) equally. For that reason alone, there will also be many individuals low in sensitivity, enjoying the advantages of saving energy by not paying particular attention to stimuli.
In humans, this innate survival strategy involves noticing and adapting to details in the environment, especially the social environment. Those with this trait are carefully observing and processing what they take in, consciously or not, and maximising what they have learned. This kind of deep processing can be difficult to observe. The sensitive individual, child or adult, is simply watching and thinking while going about life, not appearing different from others. Just processing more. One can imagine that, when an adaptive behaviour is decided on based on this processing, the change may be gradual, or it might occur suddenly, before others make the same move – perhaps taking a shortcut, changing one’s diet, or buying something on sale before others have noticed the reduced price. (A revision of the HSP scale, HSP-R, attempts to highlight more the depth processing aspect.)
While information for HSPs is all over the internet, the trait is still not very well understood. One reason is the central fact that depth of processing, which is largely invisible, is the key to all the rest. Another confounding element is differential susceptibility: because HSPs are tirelessly processing their experiences, they are affected more positively than others in good environments, especially in childhood, and more negatively affected than others in bad environments. Therefore there are quite a few HSPs suffering from anxiety, depression and shyness due to difficult childhoods, and they are more visible than HSPs with good-enough childhoods.
The good news is that highly sensitive people are more positively affected than others by interventions. The bad news is that stress is also more damaging to HSPs, and more likely to be correlated with physical illnesses. After decades of studies finding more illnesses in HSPs, a crucial study concluded that stress was the underlying reason for these illnesses, not simply having the trait. The HSPs I sometimes call ‘high functioning’ may not even be aware of their trait or, if they have learned about it, have found the suggestions useful and moved on. They are mostly invisible, except for their creativity, deep thinking and empathy for others. They are not angels but, having enjoyed a good upbringing, are often very nice people.
HSPs are difficult to identify for at least three other reasons. Sensitive men are not noticed because the cultural stereotype of sensitivity in the West is that it is feminine and somewhat of a weakness. So the equal numbers of male HSPs quite understandably may hide their trait, consciously or unconsciously.
If they suggest a hike, they’ve considered the time of day, the shade, sun and wind, and the distance from others
Another violation of the stereotype of a sensitive person is that many are extraverts. Thus, though they may need time alone to recover from overstimulation, they enjoy being in groups and having a wide circle of friends. About half of HSPs have another innate trait: seeking novelty and high sensation. They are easily bored and love new things. I am one of those. It’s like driving with one foot on the gas and one on the brake. Yet neither extraversion nor high sensation-seeking fit the stereotype of HSPs as shy homebodies.
In brief, if you want to be sure you are dealing with a highly sensitive person, watch for signs of depth of processing. For example, their ideas are usually well thought-out. If they suggest where to go for a hike, they have probably considered the time of day, the aspect of shade and sun, the wind, and the distance from other hikers, among other pertinent details. They may prefer not to give an opinion, however. In a committee, for example, or a family, their opinion may differ from the majority, and the HSP may stay silent, wanting to avoid conflict or people being tired of the HSP usually being right.
Another way you can spot an HSP, of course, is their need for downtime and recovery after they have been overstimulated – or when they feel they will soon become so if they do not stop. If they are ‘high functioning’, having grown up in an environment where they felt respected, they may have their downtime planned into their lives seamlessly. When they have had enough, they learn to say: ‘That isn’t going to work for me’ without further explanation. Having clear boundaries like this is a necessity for HSPs. In a sense they are born with thin boundaries, letting in more than others, including the feelings of others, and thus they are inevitably aware of others’ needs.
The subject of boundaries brings me to the five key needs of HSPs, a list that has emerged from my years of experience with them.
First, they need to believe the trait is real. I suggest reading some of the research, easily found with an academic search engine under the terms ‘sensory processing sensitivity’, ‘environmental sensitivity’, ‘highly sensitive person’, or the ‘highly sensitive person scale’.
Second, they need to reframe their experiences, especially the painful ones from childhood that perhaps shaped their identity. But they may also need to reframe some of their choices in adulthood, around career or relationships, or reevaluate seeming failures in these areas. Maybe they were always embarrassed that they had only one child (or none), but unlike so many other parents, they found parenting too demanding. They may have always regretted turning down a job that involved a lot of travel or a long commute, ‘just because it felt like too much’. So many self-doubts and regrets can be reframed as inevitable given their high sensitivity.
HSPs need to understand that everyone does best when in their optimal level of arousal. People drink coffee to get themselves into that optimal zone. But once a person has passed beyond that zone and becomes overstimulated, they can have trouble thinking clearly and even lose physical coordination. The feeling is often confused with anxiety or can lead to anxiety about failing. This can happen to HSPs merely by being observed, but especially during a performance evaluation. With enough ‘over’-preparation, HSPs can manage these situations, but often they do not realise the need to do this, thinking that there is just something wrong with them.
They need to avoid reaching debilitating levels of overstimulation, and need to plan for adequate downtime
Thirdly, they may need some concerted time healing from the past, usually with a psychotherapist who understands HSPs. To help HSPs find the right professionals, on my website I maintain a list of therapists who have passed a continuing education course and test that I devised in order to be on that list. Being on the list does not mean they are good therapists in other ways, but they do at least understand HSPs.
A fourth need is to change one’s lifestyle. In particular, HSPs need to avoid reaching debilitating levels of overstimulation. They need to plan for adequate downtime. After a lifetime of trying to be like the majority, this can require some effort and even willpower to arrange work and family life so that it is how it should be for the individual HSP, while taking into consideration their responsibilities to others. Lifestyle changes pay off for the HSP and everyone around them, allowing them to make their trait a real asset.
The fifth need is to spend at least a few hours, at least once, in a group of HSPs. In such an all-HSP gathering, the trait feels so real. A group of HSPs is usually quieter, more polite, and less demanding than the average group. This brings up another point: HSPs need to remember when not around other HSPs to turn up their ‘volume’. They need to be straightforward, even brash to the degree they can. They cannot just hint about their needs, hoping they have been heard.
I chose to end with the above five practical suggestions because I know many HSPs or their family members and friends may read this. As always, I want to help them all, as much as I can. This article is not about me, but about those who have found an important part of themselves through my accidental encounter with high sensitivity. So many HSPs have said: ‘This has changed my life’. This essay may change a few more.
