Sensory Processing Sensitivity: Review of the Research

Elaine N. Aron, Ph.D.

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Highly Sensitive Therapists’ Retreat

July 6, 2018

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Outline

• The concept and its measurement
• Differential susceptibility
• Behavior/emotion experiments
• Neural correlates
• Heritability and genetic correlates
• Some other studies of interest and some issues
• Summary

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Outline

• The concept and its measurement
• Differential susceptibility
• Behavior/emotion experiments
• Neural correlates
• Heritability and genetic correlates
• Some other studies of interest and some issues
• Summary

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What is Sensory Processing Sensitivity?

DOES

• D: Depth of processing: Preference to process information more thoroughly
• O: Easily Overstimulated
• E: Greater Emotional reactivity (both positive and negative) and Empathy:
• S: More aware of Subtle stimuli;

ALSO:

More responsive to environment (“vantage sensitivity”; “differential susceptibility”)

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Correlations with SPS (From Pluess et al., 2018)

* Negatives (Standard scales)

• Behavioral Inhibition System .55**
• Negative Emotionality .38**
• Negative Affect .15*

* Positives (Standard scales)

• Behavioral Activation system .42**
• Positive Emotionality .29**
• Positive Affect .16*

(Similar results in Lionetti et al, 2018; Smolewska et al., 2006;

also found in brain activation studies)

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Greater emotional responsiveness to both positive and negative facilitates depth of processing and is probably the cause of differential susceptibility

Two Strategies

Two strategies: In over 100 species (Wolf et al., 2008, PNAS)

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“Do it once and do it right”

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“Go for it; if wrong, go for it again”

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That is:

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Responsive, reflective, reactive, sensitive

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Nonresponsive, impulsive, low reactivity, non-sensitive

The Two Strategies

• Animal research examples:
• Fruit flies—sitters vs. rovers, neural complexity
• Pumpkinseed sunfish—bold vs. timid; or responsive vs. not responsive
• Primates—Uptight vs. laid back, actually more and less responsive

Probably Negative Frequency Dependent �(Wolf et al,, 2008)

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• Always a minority (in humans, 15-30%) because it’s no advantage if everyone were sensitive
• For example: No advantage to a short cut through traffic if everyone uses it.
• But does have disadvantage of taking time and energy and does not always improve results.

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History of Development of the Concept� (Aron & Aron, 1997, JPSP)

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• Early and current views on introversion
• Interviews
• Relation to infant/child temperament research
• Inhibitedness
• Shyness
• Why a new term was needed

Clarifying What SPS is Not

• Not introversion (30% are extraverts)

• Not a disorder (not SPD, ASD or high functioning autism, ADHD, PTSD, etc.)

• Not more common in women (equal numbers of men and women)

• Not something you can eliminate (it is largely innate)

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Study Developing the HSP Scale �(“SPS and its relation to I and N;” Aron & Aron, 1997)�

7 studies, total N = 1342 (mostly student samples; interviews and random digit dialing were community samples)

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Interviews, 39 (18-66 yrs., roughly 4 in each decade).

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Creation of first scale, then number of items reduced to obtain better alpha

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Comparison to various scales, including Big Five, and determined it was not simply neuroticism or introversion (using 4 different measures of I-E, correlation was moderate)

Big 5 failed to account for 71% of variance in HSP Scale scores

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Distinctiveness from Introversion and Neuroticism (Aron & Aron JPSP, 1997, Study 2)

Partial Correlations

Direct HSP I&N

Correlations controlling controlling HSP I & N for I&N for HSP

Daylight sensitivity .32** .27** .26** .12

Alcohol sensitivity .39** .24** .36** .09

Time alone .22** .32** .02 .29**

Feelings well up .28** .38** .11 .28**

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New Developments of HSP Scale: Three factors or one?�

Three subfactors had been found (e.g.,Smolewska,et al., 2006)�

• EOE: Ease of excitation (e.g., “. . . changes in your life shake you up”)

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• LST: Low sensory threshold (e.g., “. . . made uncomfortable by loud noises.”)

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• AES: Aesthetic sensitivity (e.g., “ . . . aware of subtleties n your environment”) (AES items mostly positively worded, reflects depth of processing)�� 

New Developments of HSP Scale

• 3 subfactors & 1 overarching factor—that is, bifactor. The bifactor pattern fits the data significantly better than a simple 3-factor model. (Lionettie et al, 2018; Pluess et al, 2018) �

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New Developments of HSP Scale�Category or Continuous Dimension?

Most traits are continuous dimensions.Taxometric analysis distinguishes continuous from categorical variables. Using this method:

- Woodward et al. (2000) found the related trait of “reactivity” assessed in sample of 599 four-month-old infants to be categorical, applying to about 10%

• Borries (2012), using multiple analysis methods with the HSP Scale in a large diverse sample of German adults (N = 898, M_age=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”

New Developments of HSP Scale

• Three distinct groups:  high, medium, and low sensitivity (Pluess et all, 2018; Leonetti et al, 2018)

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New Developments of HSP Scale

12-item measure for older children and adolescents (Pluess et al, 2018)

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New Developments of HSP Scale: Improving Measurement of �Depth of Processing�

• Only 4 of 27 items somewhat on Depth:
• Do you have a rich, complex inner life?
• Are you deeply moved by the arts or music?
• Are you conscientious?
• When people are uncomfortable in a physical environment do you tend to know what needs to be done to make it more comfortable (like changing the lighting or the seating)?

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These four are part of the 7-item AES factor, of which all are positively worded; AES factor is probably simply positive items.

Depth of processing items now being tested.

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Outline

• The concept and its measurement
• Differential susceptibility
• Behavior/emotion experiments
• Neural correlates
• Heritability and genetic correlates
• Some other studies of interest and some issues
• Summary

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Does SPS Interact with Effects of Childhood Environment to Predict Negative Affectivity? ��Tentative Interaction Model

(Aron et al., PSPB, 2005)

Tentative Interaction Model�(another illustration)

(Aron et al., PSPB, 2005)

Highly Sensitive Individuals

Not Highly Sensitive Individuals

Some Supporting Evidence for Interaction (Aron et al., PSPB, 2005)

Note: Any negative bias by HSPs in recall of childhood environment would lead to opposite effects of those found here. (That is, high NA HSPs are actually reporting less adverse childhoods than equally high NA nonHSPs.)

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(Basic result replicated for depression by Liss et al., 2005)

Some Experimental Evidence �(Aron et al., PSPB, 2005, Study 4)

• N = 160
• Brief HSP Scale
• All completed supposed standard questionnaire
• Start & end assessed negative mood
• In middle, took either very easy or very difficult “Applied Reasoning Ability” test

�A "For Better and Worse" Interaction (Belsky & Pluess, 2009; Ellis et al;, 2011)�� 

• Challenges previous widely-held assumption:
• SPS (and other low frequency temperaments) is NOT only a vulnerability factor
• Meta-analysis:
• A number of susceptibility indicators (including SPS):
• Behavioral (e.g., “irritable” infants)
• Genetic
• Physiological reactivity
• HSP Scale
• Under right conditions (“goodness of fit”), SPS is an advantage

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Vantage Sensitivity�Pluess & Belsky (2012, Psych Bull; after Manuck, 2011)

• Focuses on the “for better” half of interaction
• “Vantage” refers to general rather than specific advantage
• “Resilience” equals vantage resistance
• Famous first study: Suomi (1997), “up tight” rhesus monkeys assigned skilled mothering = high social status

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An Intervention that succeeded only for those high on the HSP Scale (Pluess & Boniwell, 2015)�

Possible Examples of Vantage Sensitivity, short serotonin allele

• Maternal responsiveness = moral internalization only with ss allele
• BEI: Rumanian orphan infants randomly assigned to skilled foster care: only those with ss allele benefited at 54 mos
• Adults: ss allele. Amplifies positive emotion in marriage and amplifies social emotions in general

Outline

• The concept and its measurement
• Differential susceptibility
• Behavior/emotion experiments
• Neural correlates
• Heritability and genetic correlates
• Some other studies of interest and some issues
• Summary

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Laboratory Visual Search Task

• On a standard visual search task, SPS associated with better performance (faster response time and fewer errors), followed by increased perceived stress (Gerstenberg, 2012).

Correlations with HSP Scale (controlling for N & E)

Response to Emotional Pictures

SPS associated with faster and more strongly valenced response to both positive and negative images (Jagiellowicz, Aron, & Aron, 2016)

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Outline

• The concept and its measurement
• Differential susceptibility
• Behavior/emotion experiments
• Neural correlates
• Heritability and genetic correlates
• Some other studies of interest and some issues
• Summary

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Neural Correlates

• More activation making fine visual distinctions (Jagiellowicz et al., 2010)

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• Interaction with cultural differences during visual judgment tasks (Aron et al, 2010)

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• Greater response to sad, neutral, and happy expresssions, esp. insula and mirror neurons (Acevedo et al., 2014)

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• Interaction of quality of childhood and response to positive and negative images (Acevedo et al, 2017)

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Neural Correlates

• More activation making fine visual distinctions (Jagiellowicz et al., 2010)

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• Interaction with cultural differences during visual judgment tasks (Aron et al, 2010)

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• Greater response to sad, neutral, and happy expressions, especially insula and mirror neurons (Acevedo et al., 2014)

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• Interaction of quality of childhood and response to positive and negative images (Acevedo et al, 2017)

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Brain Activation � Minor vs. Major Scene Changes

• HSP Scale scores correlated with greater activation in response to minor changes (vs. major changes) in
• Secondary visual areas
• Visual association areas
• Visual-motor coordination areas
• Results remain (and stronger) controlling for neuroticism and extraversion

Example: Left middle temporal gyrus (MNI: –52, 56, 6) SPS residual association for minor > major change

Neural Correlates

• More activation making fine visual distinctions (Jagiellowicz et al., 2010)

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• Interaction with cultural differences during visual judgment tasks (Aron et al, 2010)

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• Greater response to sad, neutral, and happy expressions, especially insula and mirror neurons (Acevedo et al., 2014)

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• Interaction of quality of childhood and response to positive and negative images (Acevedo et al, 2017)

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Background from many previous studies �

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• Interdependent cultures (e.g., East Asians) perform better incorporating context

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• Independent cultures (e.g., Americans) perform better ignoring context

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• Applies to both social relations and simple perceptual judgments

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Culture & Brain Response to Basic Visual Judgments �(Hedden et al., Psych Science, 2008)

• 10 East Asians recently in U.S.
• 10 Americans of European descent
• fMRI scan while making judgments of size of line in a box
• Some judgments relative - require attending to context (box size)
• Some judgments absolute - require ignoring context (box size)

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Culture & Brain Response to Basic Visual Judgments �(Hedden et al., Psych Science, 2008)

Brain system (from parietal regions) known to be engaged during attentionally demanding mental tasks

• was more active for East Asians during judgments ignoring context
• was more active for Americans during judgments attending to context

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Relation to SPS�.

Hypothesis:

Highly sensitive individuals, because they process information more deeply, should be less affected by cultural context

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Results�(Aron et al., 2010, SCAN)

Results (continued)�(Aron et al., 2010, SCAN)

Neural Correlates

• More activation making fine visual distinctions (Jagiellowicz et al., 2010)

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• Interaction with cultural differences during visual judgment tasks (Aron et al, 2010)

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• Greater response to sad, neutral, and happy expressions, especially insula and mirror neurons (Acevedo et al., 2014)

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• Interaction of quality of childhood and response to positive and negative images (Acevedo et al, 2017)

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Greater neural response to emotional states of others, especially partners� (Acevedo et al., 2014, Brain & Behavior)

• 18 newly marrieds scanned while viewing photos of partner and of strangers displaying positive, negative, or neutral facial expressions.

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• SPS associated with stronger neural activation in response to others’ positive and negative emotional expressions--regions involved in awareness, empathy, unconscious preparation to act, and meaning-making

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• Results significantly stronger for partners (& to positive stimuli)

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Partner Happy-versus-Stranger Happy

Partner Sad-versus-Stranger Sad contrast

Neural Correlates

• More activation making fine visual distinctions (Jagiellowicz et al., 2010)

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• Interaction with cultural differences during visual judgment tasks (Aron et al, 2010)

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• Greater response to sad, neutral, and happy expressions, especially insula and mirror neurons (Acevedo et al., 2014)

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• Interaction of quality of childhood and response to positive and negative images (Acevedo et al, 2017)

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Interaction of quality of childhood and response to positive and negative images (Acevedo et al, 2017)

• 14 participants were shown standard (IAPS) positive, negative, and neutral stimuli.
• The higher the SPS…
• for all emotional stimuli, more activation in areas processing emotional memory, learning, physiological homeostasis, awareness, reflective thinking, and integration of information
• for positive stimuli, more in reward processing, self-other integration (insula), calm, and satiation areas
• for negative stimuli, more in areas processing negative stimuli (amygdala) plus deactivation of reward areas
• Replication: Perceptual processing results replicate two prior studies

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• Negative images: SPS X Childhood interaction

Interaction of quality of childhood and response to positive and negative images (Acevedo et al, 2017)

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Negative Positive

Parenting

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Notes: mPFC is an emotion regulation area

Same interaction for Amygdala

Lo HSP

Hi HSP

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• Positive images: SPS X Childhood interaction

Interaction of quality of childhood and response to positive and negative images (Acevedo et al, 2017)

Similar results were found for caudate tail and hippocampus

Hi HSP

Lo HSP

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Negative Positive

Parenting

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VTA is a major reward area

Outline

• The concept and its measurement
• Differential susceptibility
• Behavior/emotion experiments
• Neural correlates
• Heritability and genetic correlates
• Some other studies of interest and some issues
• Summary

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Heritablity and Genetic Correlates:

• Serotonin--three variations: 5-HTTLPR short/short, short/long, and long/long genotype; associated with differential susceptibility; correlation of short with HSP Scale (Licht it al., 2011)
• Dopamine: 98 genes with variants, 10 loci on 7 genes correlated with HSP Scale (Chen et al., 2011)
• Reasons for caution: Field of behavioral genetics in flux, more stringent criteria for single gene correlations or use genome-wide methods.
• Heritability—twin studies, HSP Scale definitely inherited but how is not clear. (Assary et al., submitted)

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Outline

• The concept and its measurement
• Differential susceptibility
• Behavior/emotion experiments
• Neural correlates
• Heritability and genetic correlates
• Some other studies of interest and some issues
• Summary

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Some other studies of Interest �

• Romantic Relationships
• more easily bored (Aron et al., 2010)
• different sexual behavior (e.g., less interest in variety, fewer bad experiences (Aron, 2006)

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• Parenting
• Perceive home as more chaotic, but also more accurate overall in perceiving how chaotic it is (Wachs, 2012)
• More stressed, but more connected (Aron & Aron, under review)

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• Work Place (analyses not controlling for N)
• More affected by stress (e.g., Evers, Rasche, & Schabracq, 2008)
• Lower well being, but supervisors rated their performance higher (Bhavani, 2011)

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Some other studies of Interest �

• Comparison of fMRI studies of SPS, Autism Spectrum, Schizophrenia, and Post-Traumatic Stress: 
• In response to social and emotional stimuli, SPS differentially engages brain regions involved in reward processing, memory, physiological homeostasis, self-other processing, empathy and awareness. (Acevedo at al, 2018)

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• Significant correlation (.26) between 6-item Awe Scale (Shiota et al., 2006) and HSP Scale (Aron, Aron & Tillman, 2019)

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• Child Behavioral Measure (Leonetti, in process)

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Issues to consider:�Norms on standard scales�

• Are measures of N, depression, and anxiety appropriately normed for those with the trait, given their stronger emotional responses?
• On 1-5 scale, total population might average 3 on these measures, but those high on trait might average 4, a level normal for this group due to greater emotional responsiveness--not because they are neurotic.
• Examples items from Big Five N scale:
• Worries a lot.
• Can be tense.
• Can be moody.
• Is emotionally stable, not easily upset (rev.)

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Issues to Consider:�HSPs who do versus do not understand the trait

• Does it matter that studies of burnout, for example, use samples in which high scorers do not know they are highly sensitive?
• Needed: A random assignment longitudinal study looking for reduced stress, health problems, and burnout, or higher self-esteem, after psychoeducation about SPS.

Outline

• The concept and its measurement
• Differential susceptibility
• Behavior/emotion experiments
• Neural correlates
• Heritability and genetic correlates
• Some other studies of interest and some issues
• Summary

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Summary

• The concept and its measurement
• Differential susceptibility
• Behavior/emotion experiments
• Neural correlates
• Heritability and genetic correlates
• Some other studies of interest and some issues

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Thank you for your attention

For pdfs of most of this research,

and a copy of these power points:

www.hsperson.com