Sensory processing sensitivity, SPS, is the accurate term for the trait behind a HSP or highly sensitive person. SPS is my preferred term because it describes the trait, rather than making the trait the defining attribute of the person. Variability in sensitivity is common across organisms and gives rise to at lease two distinct behavioral responses, proactive and reactive. Writing about this variability Dr. Michael Pluess says, “Individual differences in the behavioral response to environmental factors can be seen across many species from pumpkinseed fish, zebra finches, mice, nonhuman primates to humans.”
Primary Characteristics of SPS/HPS are DOES: Depth of processing, Overstimulation, Emotional sensitivity and empathy, and sensing the Subtle.
Secondary Characteristics: DS or Differential Susceptibility: SPS children who did not receive the engagement from adults that would cultivate a sense of safety, validation, and encouragement are more likely than others to be depressed, anxious, or shy, whereas those who received the necessary engagement as children do better in life than those who are not so sensitive. They are more confident and less likely to be depressed or highly anxious.
Pronouns: I use the terms “our and “we” to refer to HSP/SPS as a way of personalizing or humanizing the trait.
|Depth of processing. Recent evidence , ,  supports earlier surveys and interviews that suggest we have strong activation of brain regions involved in reflection, planning, and social attachments. Regions include the mirror neuron network (empathy), insula (gathers information from many areas, thought to be the seat of consciousness), the default mode network (reflection while not goal seeking), the body’s wider nervous system (gut feelings), the cingulate gyrus (helps express emotions through gestures, etc.), and the premotor area.|
Good Feelings. intense emotions cuts both ways, we feel all emotions more intensely, which means we feel joy and contentment with greater intensity, but also sadness, grief and anxiety with the same intensity. 
Sense the subtle. When rested we pick up on more nonverbal body language and facial expressions, but when tired we pick up on less that others. When rested we see more subtle distinctions and can discern better the differences between delicate and fragile qualities, including scents and beauty.
Enjoy Art. As a secondary emergent quality to emotional sensitivity and sensing the subtle we tend to enjoy art and music deeply.
Comfortable with BEING as much as doing, including spiritual experiences that require contemplation. Able to “be here now” and “savor each moment.”
finding meaning. When interacting with the environment, the brain areas of HSPs that do complex processing of sensory information are more active than other people. Not so much the areas that recognize words, but the areas that catch the subtle meaning of words.
finding the hidden, especially hidden patterns and resources. We fit the classic reactive personality in the “reactive vs proactive” dichotomy outlined in theories from the 1990s . Reactive individuals are good at deeply processing experiences to find or uncover connections in the data, larger patterns, and relationships that others miss. This provides us with the survival advantage of long-term planning and extracting resources from known territory. This characteristic is confirmed in cross species analysis  and laboratory testing .
See the Positive and Potential. Our brains tend to react more to all stimulus, but we react as much or more to positive emotions, such as curiosity, anticipation of success (using that short cut others don’t know) as we do to the negative. To some extent, this counteracts the negativity bias.
UNCONVENTIONAL. Orientation towards the positive combined with being adept at seeing what others miss gives greater appreciation for context and helps look beyond conditioning to see how things “really are” .
Rich inner life. The high degree of processing, and the ability to sense and distinguish subtlety, gives rise to a strong internal process of mapping, of what is important and worth contemplating.
Empathic. The greater reactivity of mirror neurons gives rise to better interpretation of other’s feelings. Because of this we know what others need to be comfortable.
LEADERSHIP. Dr. Aron references John Hughes post regarding leadership in a Forbes article entitled, “Why Highly Sensitive People Make the Best Leaders.” The outstanding characteristic of HSP leaders is that we let others shine and make space for those we supervise to express their ideas. We also think about how to empower those under our leadership and we are good at assessing threats to a business or team.
Good at Getting along with others. Because of enhanced empathy and awareness of others feelings we can anticipate the needs of people in our family, work group, or team, and bring the resources that will help people excel. In addition we can anticipate conflicts that are likely to derail teams and prepare for them. Generally well mannered and considerate.
Reciprocal reinforcement for caring. We don’t process anything unless we care about it. So emotional responsiveness pushes depth of processing and depth of processing provides more material to have feelings about.
Conscientious. Dr. Aron in a recent interview  for the Good Life Project said that along with being high performers, HSP are conscientious. We generally work for and take pride in good outcome.
Comfortable with self. Generally we can handle solitude, even if extroverted because of our rich inner life and need to process.
References (4 through 8 from Dr. Aaron PowerPoint.)
 (From Pluess et al., 2018), also https://highlysensitiverefuge.com/emotions-hit-highly-sensitive-people-harder-science/
 “Biological Sensitivity to Context Theory” (BSCT) developed by W.T. Boyce and B.J. Ellis; and the “Differential Susceptibility Theory” (DST) developed by Jay Belsky and Michael Pluess.
 (Wolf et al., 2008, PNAS)
 Borries (2012), using multiple analysis methods with the HSP Scale in a large diverse sample of German adults (N = 898, Mage=36), results converged on 15-20% being HSPs. Borries conclusion: “HSPs exist, forming an independent group of people who are qualitatively distinct from all the others concerning their way to perceive and process stimuli”
 On a standard visual search task, SPS associated with better performance (faster response time and fewer errors), followed by increased perceived stress (Gerstenberg, 2012).
 Interaction with cultural differences during visual judgment tasks (Aron et al, 2010)
 Heritability—twin studies indicate HSP inherited but how is not clear. (Assary et al., submitted)
 Good Life Project Podcase: https://podcasts.apple.com/us/podcast/elaine-aron-phd-highly-sensitive-people/id647826736?i=1000528565509
 Individual Differences in Environmental Sensitivity, Michael Pluess, http://www.philosonic.com/michaelpluess_construction/Files/Pluess_2015_Individual%20Differences%20in%20Environmental%20Sensitivity.pdf
|Slowness and rumination. The deep processing of information and making sense of complex situations can cause some HSP to slow down or ruminate. Action is delayed till processing is done. Decisions are usually the right ones, but not quick.|
Vulnerability to ovERSTIMULATION requires strong boundaries. We are easily overwhelmed by bright lights, strong smells, coarse fabrics, loud noise, and too much stimulus. Our brain becomes inefficient during stress and conflict. We need to learn and establish boundaries for both protection from overstimulation, and protection from being taken advantage of. We often simply avoid situations that overstimulate or are upsetting, including intense social interactions, loud or confrontational people, violent movies and TV shows.
Chaotic Environments are Challenging. Prefer calm & minimally chaotic environments, don’t function well in noisy or busy environments.
Defensiveness. Overstimulation and boundary challenges can evoke a threat response and defensive behaviour. In this state we function less well than non-HSP.
Bad Feelings. intense emotions cuts both ways, we feel all emotions more intensely, which means we feel joy and contentment with greater intensity, but also sadness, grief and anxiety with the same intensity. 
Empathy Fatigue. We are easily affected by the moods and energy of those around us, and can become overloaded by “feeling” the feelings of others.
FEEL STRESS MORE AT WORK. Preliminary study of HSP in the Work Place suggests we may be more affected by stress (e.g., Evers, Rasche, & Schabracq, 2008) and have a lower than average sense of well being, even though supervisors rated our performance higher (Bhavani, 2011).
Corporate Culture creates Barriers. “A team led by Mark C Frame from Middle Tennessee State University finds that the higher you go on the corporate ladder, the more you’re among people who put a lot of stock in assertiveness and independence — what psychologists call “agentic” qualities — rather than on such things as caring about others’ feelings.” – Dr. Aaron
Deadlines can be counterproductive. Deadlines push us out of calm and focus and reduce our ability to process and understand. We feel rattled when we have a lot to do in a short amount of time and so we become less efficient.
Minority Creates social exclusion. As 15 to 20% of the population we are noticeably different in key areas from the majority. In addition our tolerance of different perspective creates suspicion from people who are under the influence of ingroup/outgroup mechanisms.
JUDGMENTS OF OTHERS FEEL LIKE THREATS. Our strong sensitive is often judged as a weakness. Dr. Aaron explained in the Good Life Project interview  that sensitive people discern early in life that they are vulnerable to judgement because of their trait. Until recently there were no terms to explain the trait and so parents often encouraged sensitive children to hide their sensitivity, “overcome it,” or “fit in.” And because of our sensitivity and deep processing we see more subtle distaste, rejection, dismissal, and rejection and remember it more. Common judgements:
You are too emotional.”
“you are too much of a people pleaser.”
“you need to man up/toughen up.”
“don’t take things so personally.”
“why are you so sensitive?”
“you’re so shy!”
“You need a thicker skin.”
Feeling of inferiority. Dr. Aaron explained in the Good Life Project interview  that as with all minority groups, this trait and the social judgement that results, can make children feel isolated and inferior. Without strong compensation by aware adults, the social judgement can cause a loss of self esteem over time as we repeatedly find our trait the source of criticism and teasing.
Long recovery time. Processing and recovery from processing takes time and resources. We need more time alone, more sleep, and more down time in general to rest in order to be our best.
Need to be Particularly Diplomatic. Group dynamics are complicated because we often see things before others, and must work harder to bring people to the same realization we have had without implying we are better in some way.