Individual differences in sensitivity: the metaphor of flowers

Individual differences in sensitivity have been observed in many species, including human beings (Wolf, Van Doom & Weissing, 2008; Nava et al., 2014; Pennisi, 2016; Krishnan, 2015).

Although sensitivity is relevant for all (given the importance of adaptation to specific environmental conditions for a successful development) some individuals seem to be significantly more sensitive than others (Aron et al., 2012; Belsky & Pluess, 2009; Ellis et al., 2011).

A large number of studies tried to explain these differences: for example, some features of temperament (Kim & Kochanska, 2012) and some genetic variants (Mitchell et al., 2014) have been associated with greater sensitivity.

Recent studies

According to empirical studies and recent theories, people differ substantially in their sensitivity.

Lionetti and colleagues, in a 2018 work, have explored the existence of different levels of sensitivity in a sample of 906 adults who have compiled “The highly sensitive person scale” (at this link there is a translation in Italian of the test published by Elaine Aron on its official website: https://hsperson.com/).

The statistical analyzes conducted by Lionetti and colleagues (2018) suggested the existence of three groups: a highly sensitive group (31%), a low sensitivity group (29%), and a third group (40%) characterized by medium sensitivity. To the three groups, the authors have chosen to refer respectively as “orchids” (high sensitivity), “lion teeth” (low sensitivity) and “tulips” (medium sensitivity), in line with the metaphor of flowers.

The main considerations carried out by the authors are summarized below, the conclusions to which they come and the main implications for research and clinical practice.

The high sensitivity: a risk factor or a protective factor?

Traditionally, the differences in sensitivity were interpreted looking at it as a vulnerability factor, according to the Diathesi-Stress model (Monroe & Simons, 1991).

According to this perspective, the most sensitive individuals are more vulnerable to the negative effects of contextual adversities (for example: negative life events), while the less sensitive individuals would prove more resilient in the face of the same negative experience.

However, this vision has been questioned by theories inspired by evolution, according to which the most sensitive individuals can not only be more conditioned by the negative effects of adverse experiences, but also more reactive to the beneficial effects of positive environmental exhibitions (Ellis & Boyce, 2008).

The high sensitivity and its components

The studio of Lionetti and Colleghi (2018) was proposed to test the existence of distinct sensitivity groups, as suggested by different theories on environmental sensitivity (Belsky & Pluess, 2009; Aron & Aron, 1997; Boyce & Ellis, 2005). But also to clarify whether the measurement of applied auto-reports, the HSP scale, measured a unitary sensitivity construct.

Originally, the HSP scale has been designed to evaluate a unidimensional sensitivity construct: the “sensorial processing sensitivity”. The study, however, showed that the data were more consistent with the existence some factors – subcomponents – of sensitivity, as listed below (even if the moderate but significant correlations between the three HSP factors suggested that a general trait of environmental sensitivity could actually exist in addition to the three subsbursts).

1. ease of excitement (EOE), that is, being easily overwhelmed by external and internal stimuli (for example: having a negative response when dealing with more stimuli simultaneously);
2. Aesthetic sensitivity (AES), (for example: to be deeply moved by the arts and music);
3. Low sensory threshold (LST), which reflects the unpleasant sensory excitement to external stimuli (for example: the reaction to intense lights and strong noises).

The investigation into the total scores and subsidies of HSP between the three different groups of sensitivity suggested that the three groups differ in the general degree of sensitivity and not in the HSP subcomponents.

Therefore, the three different groups seemed to remain along a continuum of general sensitivity, which in turn was constituted as a quantitative and normally distributed trait.

High, medium and low sensitivity: the overcoming of the dichotomous vision

The existence of a highly sensitive group (which represents about 31% of the population) detected by the authors is consistent with all the theories on environmental sensitivity (Belsky & Pluess, 2009), as well as a large number of empirical studies, which report that a minority of the population seems to be highly sensitive (Belsky & Pluess, 2013; Suomi, 1997).

The novelty introduced by Lionetti and colleagues (2018) concerns the fact that the least sensitive individuals fall into two distinct groups rather than one: in other words, sensitivity would not be a binary trait as implicated by multiple theories (Koolhaas et al., 1999) and by empirical research on reactivity/responsiveness in various animal models (Stamps, 2016).

Consequently, the dichotomous metaphor “lion’s teeth” vs “orchid” – even if intuitively understandable and useful when explaining the inter -individual differences in sensitivity – is not supported by this study.

In summary, while some people are highly sensitive (orchids), most have a medium sensitivity (tulips) and a substantial minority are characterized by a particularly low sensitivity (lion teeth).

Orchids, tulips and lion teeth: what differences in personality?

Another purpose of the study was to evaluate any differences in terms of personality traits in the various sensitivity groups.

The authors found that the “orchids” had significantly higher levels of neuroticism and positive emotional reactivity, while they were lower in extroversion than the other groups.

The “lion teeth” had higher levels of extroversion but lower scores of neuroticism and positive emotional reactivity. In summary, the “orchids” tended to be more introverted and inclined to negative emotionality than the other groups.

However, they seemed to show a stronger emotional response to positive experiences. The “lion teeth” were more extroverted and less anxious but at the same time less reactive to the positive induction of mood. Finally, the “tulips” occupied the way in relation to these sections.

What implications for psychotherapy?

An important implication of the sensitivity groups highlighted by the authors concerned the fact that the “orchids” could be more reactive to the psychological/psychotherapeutic intervention than the “lion teeth”, precisely because of their greater sensitivity to positive exposures (that is, positive emotional reactivity).

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