emphasizes increased responsiveness to positive experiences. Researchers such as Smolewska et al. (2006) said positive outcomes were more common in individuals with high aesthetic sensitivity, who tend to experience heightened positive emotions in response to rewarding stimuli and more likely to score high on "openness" on the Big Five factors model. Research in evolutionary biology provides evidence that the trait of SPS can be observed, under various terms, in over 100 nonhuman species, Aron writing that the SPS trait is meant to encompass what personality psychologists have described under various other names. Conversely, Aron has distinguished SPS from what she considers it is not, explicitly distinguishing high SPS from possibly similar-appearing traits or disorders (such as shyness, sensation-seeking, sensory processing disorder, and autism), and further, that SPS may be a basic variable that may underlie multiple other trait differences (such as introversion versus extraversion). Contrary to common misconception, according to Aron HSPs include both introverts and extroverts, and may be simultaneously high-sensation seeking and cautious. In humans and other species, responsive and unresponsive individuals coexist and consistently display different levels of responsiveness to environmental stimuli, the different levels of responsiveness having corresponding evolutionary costs and benefits. This observation parallels Aron's assertion that high SPS is not a disorder, but rather a personality trait with attendant advantages and disadvantages. Accordingly, Aron cautions medical professionals against prescribing psychoactive medications to "cure" the trait, which may or may not coexist with an actual disorder. By 2015 the trait had been documented at various levels of study, including temperament and behavior psychology, brain function and neuronal sensitization, and genetics. For example, genetic studies provide evidence that higher levels of SPS are linked to the serotonin transporter 5-HTTLPR short/short genotype, polymorphisms in dopamine neurotransmitter genes, and the ADRA2b norepinephrine-related gene variant. HSP Scale score patterns in adults were thought to be distributed as a dichotomous categorical variable with a break point between 10% and 35%, with Aron choosing a cut-off of the highest-scoring 20% of individuals to define the HSP category. A 2019 review article stated that findings suggest people fall into three sensitivity groups along a normal distribution sensitivity continuum. See also Sources and notes External links Sensitivityresearch.com, website run by researchers. Evolutionary psychology Neuropsychology Personality theories Personality traits Personality typologies