Actually, there is so much more research being done, especially in Europe, that I can barely keep up, so I have selected what I believe to be the best. You will see Michael Pluess’ name on several. He is at Queen Mary University in London, along with Francesca Leonetti, a postdoctoral student studying with him. They are doing great research, finding new angles to SPS (which is the term used in scientific contexts for your trait), developing the HSP Scale in various ways, and adding new points to what we know. We are so glad they are moving forward in this way. It takes some of the weight off of Art and me, as we see quality research being done without us!
First I will discuss articles in which I was one of the authors.
The “Relationship between the Temperament Trait of Sensory Processing Sensitivity and Emotional Reactivity” was published in 2016, in the journal Social Behavior and Personality. The first author is Jadzia Jagiellowicz, along with Art and me. It is based on data Jadzia gathered while at Stony Brook University. (She is now in Cambridge, Ontario. https://www.highlysensitivesociety.com/ ). 96 participants (1/2 HSPs and 1/2 those especially low on the HSP Scale) rated standard emotional-arousing pictures for how positive and negative they seemed and how aroused the participant was by looking at them. HSPs rated the pictures, and especially the positive ones, as significantly more intense emotionally. They also responded faster to the positive pictures. HSPs who reported having high-quality parenting also reported greater arousal in response to positive pictures than those low in sensitivity.
These results give us some insight as to why HSPs exhibit “differential susceptibility,” suffering more in bad environments but doing especially well in good ones. It seems that in good environments they may pay more attention to positive stimuli relative to negative and react more strongly. This is even more so if they have had good parenting, when they must have paid particular attention to positive experiences, probably some of them quite subtle such as a parent’s slight smile of approval or delight.
This study, “Sensory Processing Sensitivity and Childhood Quality’s Effects
on Neural Responses to Emotional Stimuli” by Bianca P. Acevedo, Jadzia Jagiellowicz, myself, Robert Marhenke, and my husband Art was just published (actually “in press” at this moment) in Clinical Neuropsychiatry. It is kind of a sister study for the one above, using 14 participants, women as it happened, half very high and half very low on the HSP Scale, and finding very similar results, but using a different method, measurement of brain activation. This is a case of triangulation—getting the same result with different methods, which is especially appreciated in science. The 14 women were viewing positive and negative images as compared to neutral ones, as in the last study, and took the same measure of quality of childhood parenting. I will not recite for you the technical names for the areas of the brain activated, but in each case these are the areas that were different for those who were high versus low on the HSP Scale.
For all images, not surprisingly to us, HSPs compared to the others showed more activation in areas associated with emotion, emotional memories, and emotion processing. For positive pictures (compared to neutral ones), SPS was more associated with areas involved in reward processing, self-other integration, calm, and satiation. This was even more the case the happier the childhood. For negative images (compared to neutral), some of the areas were the same (having to do with processing generally) but others were as you would expect with negative emotion, but again, many areas were different or increased for HSPs. However, a result of particular importance was, again, how much viewing the negative images was affected by having a better childhood, in that there was more activation in areas involved in emotion regulation and self-control.
In sum, throughout the study, HSPs showed more brain activation while looking at the emotional pictures, just as they showed more arousal or emotional responsiveness in the study above if they had had good childhoods and were also more affected by poor ones. But the huge importance of this study and the one above is that they further validate differential susceptibility—that is, HSPs benefit more from a better childhood and are harmed more a poorer childhood. We can imagine the “harmed more” effect, but these studies allow us to see how positive environments really do lead to a deeper processing of positive stimuli in HSPs. In addition, such a childhood increases especially strongly their self-awareness, arousal, self-control, and calm, which are so important when responding to any emotion-laden situation.
What if you grew up in a poor environment? Overall, HSPs also respond more to positive interventions. See the first study under “studies we were not involved in.” I am sure that this greater positive reaction will extend to psychotherapy (if the therapist provides a positive environment) and probably many more “interventions.” I predict that will include simply learning you are highly sensitive and that in many ways there is nothing wrong with you, since so much harm can be done in childhood by parents not understanding your sensitivity. So perhaps you are already living in a more positive inner and hopefully outer environment. Remember, your childhood need not cause you to feel one down.
Environmental Sensitivity in Children: Development of the Highly Sensitive Child Scale and Identification of Sensitivity Groups was by Michael Pluess, Elham Assary, Francesca Lionetti, Kathryn J Lester, Eva Krapohl, plus me and Art (complex studies often have many authors, each with their own expertise and contribution). It was published in Developmental Psychology (a particularly prestigious scientific journal). This study is rather statistical, but partly involved creating a short 12-item HSC scale for children and adolescents.
What was mainly important to us, although probably not to most of you, was that we were able to do a “bifactor analysis,” in which we found three factors (sets of items that group together) plus clear evidence for one overarching factor of plain old sensitivity. The three are (a) Aesthetic Sensitivity (e.g., being deeply moved by arts and music; having a rich, complex inner life, being conscientious); (b) Low Sensory Threshold (unpleasant sensory experiences–e.g., reaction to bright lights and loud noises; avoiding violent media); and (c) Ease of Excitation, referring to being easily overwhelmed–(e.g., being negatively affected by having a lot going on or by being hungry).
The three factors have been made much of by other researchers, even though the researcher originally finding them also said the single inclusive factor was very present as well. Sub-factors of course can only sort the items in the scale. In my original interviews from which we constructed the scales, of course I heard more about the most noticeable part of being HS, being easily overwhelmed and to some degree noticing subtle stimuli—the “O” and “S” of DOES. I had not yet conceptualized the trait as having four aspects, DOES, with “D” for depth of processing and “E” for emotional responsiveness and empathy so they were largely left out and certainly not identified as such at that time. It is much harder to learn from interviews about D and E.
Actually, the 6 items of the “Aesthetic” factor are more about depth of processing, but the researchers understandably did not see that. Besides the 3 items above in parentheses—being deeply moved by arts and music; having a rich, complex inner life; and being conscientious—the aesthetic sensitivity group of items includes knowing what to do to make people more comfortable in an environment, being aware of subtleties, and noticing fine scents, tastes, etcetera. You can see why it might seem more like something aesthetic, but what about the item about conscientiousness? A deep inner life? Oh well.
There is actually only one item for empathy (do others’ moods affect you, plus maybe noticing in a physical environment what needs to be done to make it more comfortable). We had some good items that did address emotion and empathy and that were strongly associated with the other items, but not quite as strongly so they were not included. We just did not see DOES back in 1996.
Back to this study, another very interesting finding was the existence of three distinct groups with different levels of what Michael Pluess likes to call environmental sensitivity. Every living being needs to be sensitive to its environment, but as we know, about 25-35% are highly sensitive (the uncertainty of the % is due to different samples). There’s a group in the middle (approx. 41-47%), whom we can say are the “medium sensitive.” Then there is a low group (20-35%).
They are probably the ones with whom we HSPs especially struggle!
The following studies we were not involved in.
One of the most exciting studies to date is “Sensory-Processing Sensitivity Predicts Treatment Response to a School-Based Depression Prevention Program: Evidence of Vantage Sensitivity.” This was done by Michael Pluess and Ilona Boniwell and published in Personality and Individual Differences. As the title says, there was a depression prevention program for 11-year-old “at risk” girls in a poor neighborhood in London, and the HSP Scale was among other measures given to them before and after they went through the program. The goal was to prevent these girls from becoming depressed over the next year, which often occurs to girls around 12 or a little older. The result? A year later the researchers found that the prevention program successfully reduced depression scores only for the girls in the top one third of scores on the HSP Scale. It was not effective at all for low-scoring girls.
This is another example of how HSPs pick up especially well on good things, probably in this case by processing the program’s information deeply. This gives us real hope that an intervention can help us if we need it, even more than it would help others.
“Sensory Processing Sensitivity as a Marker of Differential Susceptibility to Parenting” was published in Developmental Psychology (remember, this is a highly respected journal), reporting a study by Meike Slagt, Judith Semon Dubas, Marcel A. G. van Aken, Bruce J. Ellis, and Maja Dekovi´c. (All but Ellis are from the Netherlands). They studied kindergarten children who had been identified by both parents and teachers as having either high negative emotion or high SPS. (Negative emotion has long been seen as the main reason for differential susceptibility.) Mothers also reported on their parenting behavior using standard measure for parents, and teachers rated the children on certain behaviors (for example, having a “hot temper,” being easily distracted, or being especially considerate). The mothers and children were measured three times over seven months, allowing for studying changes over time.
The results are a bit complex, but basically associations between parenting and child behavior did not depend on children’s negative emotionality. Sensory processing sensitivity, however, interacted with both changes in negative parenting and changes in positive parenting in predicting negative behavior seven months later, so that improvements in parenting led to less negative behaviors and parenting becoming more negative led to more negative behaviors, all much more so in HSCs. (For some reason the exact opposite was true for children who were not HSCs.) Why changes gave the only results may be because HSCs tend to adapt to the parenting (in this study, mothering) they are receiving, whatever it is, but have more trouble—get angry, distracted, and so forth at school—if their mother’s behavior changes. (SPS and parenting was not related to positive social behavior. One reason may be that these children, whether HSCs or not, did not vary that much on positive social behavior, coming from a relatively high socioeconomic level. Perhaps, for many possible reasons, children from poorer or less educated families have less chance to learn these behaviors.) The authors conclude that, depending on the interaction, there was support either for the idea of differential susceptibility (“for better and for worse”) or vantage sensitivity (just “for better”–HSCs simply benefited more from a positive environment).
Here is still more evidence for SPS leading to differential susceptibility, this time from children, not adults reporting about their childhoods. The long-standing importance of negative emotionality, mainly in infancy, did not support differential susceptibility applying to this trait, as it had in the past. This is almost surely because signs of negative emotionality in infancy was mixed up with SPS. That is, some of the “negative” infants were negative only due to being overstimulated and parents not understanding their child’s needs. Sometimes infants were tested in the laboratory for negativity, by seeing their reaction to being held down or pricked with a pin on the foot!
I remember shortly after beginning this research going to a conference on temperament and nervously standing up to suggest, after someone presented a study on negative infants, that maybe this negativity could sometimes be caused by sensitivity. I added that labeling infants as negative might be misleading or sometimes even harmful for all involved, but no one got it at the time. Years later, here is an excellent study that addressed this. When the two behaviors were separated out in kindergartners, of being negative (easy to observe) and behaviors suggesting sensitivity (a little tricker to see and something parents had not been asked about much in the past), SPS was clearly the stronger predictor. How satisfying.
So when you see babies crying and parents saying, “this kid is so difficult—not like our first one at all (or not like other parents’ babies, who are so easy),” you might get up the courage to say, “Your baby could just be highly sensitive.” Then be ready to answer more questions. “Well, about 20%… Equal number of boys and girls… Easily overstimulated at this age because parents are the ones who control a baby’s level of stimulation. You can do your best, as I’m sure you are, but if you don’t understand… You might try…”
The next study was about “Sensory-Processing Sensitivity, Dispositional Mindfulness and Negative Psychological Symptoms,” done by Kaitlyn Bakker and Richard Moulding in Australia and published in Personality and Individual Differences. They noted that SPS is often associated with depression and anxiety, but perhaps there are things that moderate those effects. Hence they measured mindfulness as a trait (not as a practice, but as the ability to attend to and be accepting of present experience). They found that while in general SPS was related to higher levels of depression, anxiety and stress, with respect to anxiety, when mindfulness and acceptance were high, HSPs were not particularly anxious.
It is easy to see how staying in the present helps us handle our emotions. Indeed, I wrote about another article about the research on handling our emotions [http://hsperson.com/emotional-regulation-and-hsps/], based on an article by the same author. Why did this attribute of being mindful not affect depression and stress? There are several possible reasons. But I am promoting a couple of reasons right now.
First, no one’s studying typical or normal highly sensitive people yet. Unless someone knows they are highly sensitive, they are living under a burden. And people in these studies generally do not know. So they are going to report greater stress because they do not yet know how to take care of themselves. They may be more depressed because they think and have always thought something is wrong with them. So I hope someday soon there will be a study of the effects on stress a year after HSPs learn about their trait and receive some good advice about it. I think that in a year, many of these HSPs will have self-corrected and have fewer problems.
My other concern about the many studies finding HSPs are more stressed, depressed, etcetera than others is that these measures were validated on 100% of the population, meaning that the “other 80%” are the largest contributors to the norms. They are the mean score, the average, so that HSPs are “too high.” I don’t know the answer to that yet, except being aware of it.
The next article, “A novel Differential Susceptibility framework for the study of nightmares: Evidence for trait sensory processing sensitivity,” was by Michelle Carr and Tore Nielsen and published in Clinical Psychology Review. It did not report new data, but based on other research proposed that SPS might be a good way to think of nightmares. As the authors explain, research on nightmares has largely focused on the nightmare itself and its associated negative consequences, framing nightmare sufferers as victims of their difficult past and the resulting psychopathology. However, there is evidence that frequent nightmare recallers are sensitive to a wide range of sensory and emotional experiences, and report vivid, bizarre and even intensely positive dream and daydream experiences. So they proposed that sensory-processing sensitivity might underlie the unique symptoms and imaginative richness found in nightmare-prone individuals, and if they can have positive dreams, then this may be a case of differential susceptibility (you remember that’s experiencing both positive and negative more strongly). “Treatment,” then, might simply mean providing individuals high in SPS with more “supportive environments” rather than thinking of them as mentally ill (YES!).
It’s nice to see someone looking into this aspect of sensitivity. Having vivid, intense dreams was an item that did not make it to the final HSP Scale but correlates with it significantly. Early in my work as a depth therapist I told my consultant, not an HSP, one of my HS patient’s dreams. He said it was so strange and complicated that she must have made it up! I of course knew she had not, partly because I have had many dreams as complicated as hers.