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Environmental sensitivity describes the ability of an individual to perceive and process information about their environment. [1] [2] [3] It is a basic trait found in many organisms that enables an individual to adapt to different environmental conditions. Levels of Environmental Sensitivity often vary considerably from individual to individual, with some being more and others less sensitive to the same conditions. Such differences have been observed across many species such as pumpkinseed fish, zebra finches, mice, non-human primates and humans, indicating that there is a biological basis to differences in sensitivity.
The concept of Environmental Sensitivity integrates multiple theories on how people respond to negative and positive experiences. These include the frameworks of Diathesis-stress model [4] and Vantage Sensitivity, [5] as well as the three leading theories on more general sensitivity: Differential Susceptibility, [6] [7] Biological Sensitivity to Context, [8] and Sensory processing sensitivity [9] (see Figure 1 for an illustration of the different models). These will be described briefly in turn, before presenting the integrative theory of Environmental Sensitivity in more detail. [1]
According to the long-standing Diathesis-stress model, people differ in their response to adverse experiences and environments, with some individuals more negatively affected by environmental stressors than others. [4] The model proposes that such differences in response result from the presence of "vulnerability" factors, which include psychological (e.g., impulsive personality), physiological (e.g., high physiological reactivity) and genetic factors (e.g., genetic variation in the serotonin transporter [5-HTTLPR short allele]). In other words, the model suggests that individuals carrying certain vulnerability factors are at greater risk of developing problems when exposed to adverse environments. While the Diathesis-stress model is helpful in understanding differences in response to negative stressors, it does not consider or describe differences in response to positive experiences.
The vantage sensitivity framework was developed in 2013 by Michael Pluess and Jay Belsky to describe individual differences in response to positive experiences and environments. While some people appear to benefit particularly strongly from positive experiences (e.g., positive parenting, supportive relationships, psychological interventions), others appear to benefit less. [5] Although a relatively new concept, a growing number of studies provides evidence to support the framework. While the Vantage Sensitivity framework considers individual differences in response to positive experiences, it does not make predictions about the response to negative experiences.
Differential susceptibility, proposed by Jay Belsky, brings the differential responses to both positive and negative experiences together in one single model. Grounded in evolutionary theory, Belsky and colleagues sought to understand why and how children differ so fundamentally in their developmental response to external influences, with some being more and others less susceptible. [6] [7] Importantly, the theory finds that more susceptible individuals are not only more negatively affected by adverse experiences (as described in the Diathesis-stress model) but also particularly positively affected by the presence of favourable conditions (as described in the Vantage Sensitivity model). According to empirical studies, Differential Susceptibility is associated with various genetic, physiological and psychological factors, some of which are described below (see Empirical Evidence). Although early research suggested that differences in individuals' susceptibility are rooted in genetic factors, more recent research has shown that susceptibility is also influenced by prenatal and early postnatal environmental factors.
The theory of Biological Sensitivity to Context by Tom Boyce and Bruce Ellis is based on evolutionary thinking and proposes that an individual's sensitivity to the environment is shaped by the quality of early life experiences. [8] For example, particularly negative or especially positive childhood environments are understood to predict greater physiological reactivity later in life. In contrast, sensitivity is expected to be lowest for individuals with childhood environments that were neither extremely beneficial nor extremely adverse.
Sensory processing sensitivity (SPS) theory by Elaine N. Aron and Arthur Aron proposes that sensitivity is a stable human trait characterized by greater awareness of sensory stimulation, behavioural inhibition, deeper cognitive processing of environmental stimuli, and higher emotional and physiological reactivity. [9] According to this theory, approximately 20% of people fall into the category of a Highly Sensitive Person (HSP), in contrast to the remaining 80% who are considered less sensitive. Furthermore, the theory suggests that the sensitivity trait is adaptive from an evolutionary perspective, and regards differences in sensitivity as genetically determined and expressed via a more sensitive central nervous system.
The broad theory of Environmental sensitivity. [1] integrates all of the listed frameworks and proposes that although all people are sensitive to their environment, some individuals tend to be more sensitive than others. Furthermore, the theory of Environmental Sensitivity suggests that people vary in their sensitivity to the environment due to differences in their ability to perceive and process information about the environment. In other words, more sensitive individuals are characterised by heightened perception as well as deeper processing of external information due to neurobiological differences in the central nervous system, which are influenced by genetic as well as environmental factors. The integrative perspective of Environmental sensitivity further proposes that whilst some individuals are more sensitive to both negative and positive experiences, others may be particularly vulnerable to adverse experiences (but not very sensitive to positive ones), whilst some may be especially responsive to positive exposure (but not vulnerable to negative ones).
Differences in sensitivity have been studied in relation to a wide range of sensitivity markers, such as genetic, physiological and psychological ones. These are now discussed in turn.
A growing number of studies provide empirical evidence to support individual differences in sensitivity at the genetic level. These include traditional Gene-environment interaction studies featuring Candidate genes, [10] [11] as well as more recent genome-wide approaches. [12] As an example for the latter, Keers et al. [13] created a polygenic score for Environmental Sensitivity based on about 25,000 gene variants across the genome and then tested whether children at the extremes of this spectrum of genetic sensitivity differed in their response to the parenting quality they received. According to the results, children with high genetic sensitivity were more likely to develop emotional problems when experiencing negative parenting but also less likely to develop problems when parenting was positive. On the other hand, children with low genetic sensitivity were not as impacted by the experience of negative or positive parenting, and did not differ from each other in emotional problems based on parenting quality. Hence, this study provides important evidence that genetic sensitivity, measured across the genome, predicts children's sensitivity to both negative and positive environmental influences.
Several empirical studies have reported differences in sensitivity to the environment in relation to individuals' physiological reactivity. Higher reactivity generally appears to reflect greater sensitivity. For example, research has shown that children with a higher physiological response to stress (indicated by the hormone cortisol) are more strongly affected by their family's financial situation. [14] More specifically, a high cortisol response in children was associated with more positive cognitive development when family income was high, but with reduced cognitive development when family income was low. In contrast, family income was less relevant for the cognitive development of children who displayed low physiological reactivity (i.e., a low cortisol response). Similarly, adolescents with high cortisol levels have been found to report more stress when experiencing school-related challenges but also the lowest stress in less demanding situations, whereas adolescents with lower cortisol levels were generally less affected by either low or high school-related challenges [15]
The majority of evidence for individual differences in sensitivity due to psychological markers of sensitivity is based on studies that investigate the interplay between infant temperament and parenting during childhood. Generally, higher fearfulness, fussiness, and negative emotionality in infancy have been associated with greater sensitivity to parenting quality. According to a large meta-analysis which summarises the findings from 84 individual studies, children that are characterised by a more sensitive temperament were more strongly affected by the parenting they receive. [16] More specifically, sensitive children were more likely to develop problems when experiencing harsh and punitive parenting but also least likely to have problems when they were raised in emotionally warm and caring environments. Less sensitive children, on the other hand, did not differ much from each other whether they received more negative or more positive parenting.
An individual's level of Environmental Sensitivity is the result of a complex interplay between genes and environmental influences across development. [1] Empirical studies suggest that genetic influences are important for the development of the trait, but only about 50% of the differences in sensitivity between people can be explained by genetic factors, with the remaining 50% being shaped by environmental influences (see Figure 2). Furthermore, the genetic component of sensitivity is most likely made up by a large number of genetic variants across the whole genome, each making a small contribution, rather than a few specific genes. Importantly, although sensitivity has a substantial genetic basis, it may be the quality of the environment when growing up that shapes this genetic potential for sensitivity further. For example, those carrying a larger number of sensitivity genes may develop a sensitivity that is more geared towards threat when growing up in a challenging or adverse environment (i.e., vulnerability as described in the Diathesis-Stress model), whereas those growing up in a predominately supportive and secure context may develop heightened sensitivity towards positive aspects of the environment (i.e., Vantage Sensitivity). Similarly, those that experienced similar levels of both negative and positive exposures during childhood may develop equal levels of sensitivity to negative and positive experiences (i.e., Differential Susceptibility).
Environmental Sensitivity proposes that sensitivity is driven primarily by a heightened sensitivity of the central nervous system (i.e., neurosensitivity)(see Figure 2 for an illustration of the neurosensitivity hypothesis). In other words, sensitive people have more sensitive brains, which perceive information about the environment more readily and process such information in greater depth. This likely involves specific structural and functional aspects of various brain regions, including the amygdala and hippocampus. [1] These characteristics of the brain are then responsible for the typical experiences and behaviours associated with high sensitivity, such as experiencing emotions more strongly, responding more strongly to stressful situations or change, having a higher physiological reactivity, processing experiences in depth by thinking a lot about them, appreciating beauty, and picking up on subtle details.
In the last few decades, researchers have identified a wide range of individual characteristics that reflect or are associated with sensitivity to environmental influences. These include specific aspects of child temperament (e.g., difficult temperament, negative emotionality, and impulsivity), physiological reactivity (e.g., high cortisol reactivity) and various genetic variants that can be combined into a polygenic score of sensitivity. However, although these characteristics are important and capture some aspects of sensitivity they cannot be considered precise measures in themselves. Given that sensitivity is a complex trait, similar to other personality dimensions, it is more helpful to measure sensitivity with questionnaires, interviews, or behavioural observations that focus on the assessment of the typical behaviours and experiences that reflect the core attributes of sensitivity (i.e., perception and processing).
A series of such sensitivity scales have been developed and are briefly described below.
The Highly Sensitive Person Scale (HSP) [9] is a 27-item self-report measure designed to assess Environmental Sensitivity in adults. Items are rated on a 7-point Likert scale from 1 = "Not at All" to 7 = "Extremely". Items search for a tendency to be easily overwhelmed by external and internal stimuli (e.g. "Do you find it unpleasant to have a lot going on at once?"), greater aesthetic awareness (e.g. "Do you seem to be aware of subtleties in your environment?"), and unpleasant sensory arousal to external stimuli (e.g. "Are you bothered by intense stimuli, like loud noises or chaotic scenes?"). The scale exists also in a brief version with 12 items. [17]
The Highly Sensitive Child (HSC) scale [18] is a 12-item self-report measure that is based on the adult HSP scale and has been designed to assess Environmental Sensitivity in children and adolescents between the ages of 8 and 18 years. Items included in the HSC scale are rated on a 7-point Likert scale from 1 = "Not at All" to 7 = "Extremely". Items are designed to capture different facets of sensitivity, such as the tendency to become mentally overwhelmed by both internal and external stimuli, greater appreciation of beauty, and overstimulation when experiencing intense sensory inputs. The HSC scale also exists in parent-rated version where parents can rate their child.
The Highly Sensitive Child – Rating System (HSC – RS) [19] is an observational measure designed to assess Environmental Sensitivity in three-year-old children. Children's responses in a series of standardised situations are observed and rated by trained experts.
Initially, several psychological theories of sensitivity differentiated between two basic groups of people: those that are highly sensitive and those that are not. [9] The assumption was that about 20% of the general population are characterised by high sensitivity. Such individuals have been compared to the "Orchid", a plant that requires optimal conditions and care in order to flourish. In contrast, the remaining 80%, thought to be less sensitive, were compared to the "Dandelion", a plant that is robust and grows under many different conditions, to reflect this group's tendency to be less affected by the quality of the environment. [8] [20] More recently, this two-group hypothesis has been challenged by several studies reporting that sensitivity is more likely a common trait that is best considered a spectrum from low to high. This means that all people are sensitive but to different degrees. These studies found that people fall into three, rather than two, distinct sensitivity groups along a spectrum of sensitivity from low (30% of the population), to medium (40%), to high (30%). [17] [18] [21] According to this research, the 40% that fall into the middle of the sensitivity continuum are referred to as "Tulips", a plant that is more delicate than the "Dandelion" but less fragile then the "Orchid".
In psychology, temperament broadly refers to consistent individual differences in behavior that are biologically based and are relatively independent of learning, system of values and attitudes.
Stress, whether physiological, biological or psychological, is an organism's response to a stressor such as an environmental condition. When stressed by stimuli that alter an organism's environment, multiple systems respond across the body. In humans and most mammals, the autonomic nervous system and hypothalamic-pituitary-adrenal (HPA) axis are the two major systems that respond to stress. Two well-known hormones that humans produce during stressful situations are adrenaline and cortisol.
The hypothalamic–pituitary–adrenal axis is a complex set of direct influences and feedback interactions among three components: the hypothalamus, the pituitary gland, and the adrenal glands. These organs and their interactions constitute the HPS axis.
Sensory processing sensitivity (SPS) is a temperamental or personality trait involving "an increased sensitivity of the central nervous system and a deeper cognitive processing of physical, social, and emotional stimuli". The trait is characterized by "a tendency to 'pause to check' in novel situations, greater sensitivity to subtle stimuli, and the engagement of deeper cognitive processing strategies for employing coping actions, all of which is driven by heightened emotional reactivity, both positive and negative".
The diathesis-stress model, also known as the vulnerability–stress model, is a psychological theory that attempts to explain a disorder, or its trajectory, as the result of an interaction between a predispositional vulnerability, the diathesis, and stress caused by life experiences. The term diathesis derives from the Greek term (διάθεσις) for a predisposition or sensibility. A diathesis can take the form of genetic, psychological, biological, or situational factors. A large range of differences exists among individuals' vulnerabilities to the development of a disorder.
Beck's cognitive triad, also known as the negative triad, is a cognitive-therapeutic view of the three key elements of a person's belief system present in depression. It was proposed by Aaron Beck in 1967. The triad forms part of his cognitive theory of depression and the concept is used as part of CBT, particularly in Beck's "Treatment of Negative Automatic Thoughts" (TNAT) approach.
Gene–environment interaction is when two different genotypes respond to environmental variation in different ways. A norm of reaction is a graph that shows the relationship between genes and environmental factors when phenotypic differences are continuous. They can help illustrate GxE interactions. When the norm of reaction is not parallel, as shown in the figure below, there is a gene by environment interaction. This indicates that each genotype responds to environmental variation in a different way. Environmental variation can be physical, chemical, biological, behavior patterns or life events.
Social rejection occurs when an individual is deliberately excluded from a social relationship or social interaction. The topic includes interpersonal rejection, romantic rejection, and familial estrangement. A person can be rejected or shunned by individuals or an entire group of people. Furthermore, rejection can be either active by bullying, teasing, or ridiculing, or passive by ignoring a person, or giving the "silent treatment". The experience of being rejected is subjective for the recipient, and it can be perceived when it is not actually present. The word "ostracism" is also commonly used to denote a process of social exclusion.
Neuroticism is a personality trait associated with negative emotions. It is one of the Big Five traits. Individuals with high scores on neuroticism are more likely than average to experience such feelings as anxiety, worry, fear, anger, frustration, envy, jealousy, pessimism, guilt, depressed mood, and loneliness. Such people are thought to respond worse to stressors and are more likely to interpret ordinary situations, such as minor frustrations, as appearing hopelessly difficult. Their behavioral responses may include procrastination, substance use, and other maladaptive behaviors, which may temporarily aid in relieving negative emotions and generating positive ones.
The differential susceptibility theory proposed by Jay Belsky is another interpretation of psychological findings that are usually discussed according to the diathesis-stress model. Both models suggest that people's development and emotional affect are differentially affected by experiences or qualities of the environment. Where the Diathesis-stress model suggests a group that is sensitive to negative environments only, the differential susceptibility hypothesis suggests a group that is sensitive to both negative and positive environments. A third model, the vantage-sensitivity model, suggests a group that is sensitive to positive environments only. All three models may be considered complementary, and have been combined into a general environmental sensitivity framework.
The biopsychological theory of personality is a model of the general biological processes relevant for human psychology, behavior, and personality. The model, proposed by research psychologist Jeffrey Alan Gray in 1970, is well-supported by subsequent research and has general acceptance among professionals.
Early childhood is a critical period in a child's life that includes ages from birth to five years old. Psychological stress is an inevitable part of life. Human beings can experience stress from an early age. Although stress is a factor for the average human being, it can be a positive or negative molding aspect in a young child's life.
Parental experience, as well as changing hormone levels during pregnancy and postpartum, cause changes in the parental brain. Displaying maternal sensitivity towards infant cues, processing those cues and being motivated to engage socially with her infant and attend to the infant's needs in any context could be described as mothering behavior and is regulated by many systems in the maternal brain. Research has shown that hormones such as oxytocin, prolactin, estradiol and progesterone are essential for the onset and the maintenance of maternal behavior in rats, and other mammals as well. Mothering behavior has also been classified within the basic drives.
Studies have found that the father is a child's preferred attachment figure in approximately 5–20% of cases. Fathers and mothers may react differently to the same behaviour in an infant, and the infant may react to the parents' behaviour differently depending on which parent performs it.
Emotional eating, also known as stress eating and emotional overeating, is defined as the "propensity to eat in response to positive and negative emotions". While the term commonly refers to eating as a means of coping with negative emotions, it sometimes includes eating for positive emotions, such as overeating when celebrating an event or to enhance an already good mood.
Personality theories of addiction are psychological models that associate personality traits or modes of thinking with an individual's proclivity for developing an addiction. Models of addiction risk that have been proposed in psychology literature include an affect dysregulation model of positive and negative psychological affects, the reinforcement sensitivity theory model of impulsiveness and behavioral inhibition, and an impulsivity model of reward sensitization and impulsiveness.
Marinus H. "Rien" van IJzendoorn is professor of human development and one of the co-leaders of Generation R at the Erasmus University Rotterdam. His work has focussed on the social, psychological, and neurobiological determinants of parenting and child development, with special emphasis on attachment, emotion regulation, differential susceptibility hypothesis, and child maltreatment.
In the context of the nature-nurture debate, interactionism is the view that all human behavioral traits develop from the interaction of both "nature" and "nurture", that is, from both genetic and environmental factors. This view further holds that genetic and environmental influences on organismal development are so closely interdependent that they are inseparable from one another. Historically, it has often been confused with the statistical concept of gene-environment interaction. Historically, interactionism has presented a limited view of the manner in which behavioral traits develop, and has simply demonstrated that "nature" and "nurture" are both necessary. Among the first biologists to propose an interactionist theory of development was Daniel Lehrman. Since then, numerous interactionist perspectives have been proposed, and the contradictions between many of these perspectives has led to much controversy in evolutionary psychology and behavioral genetics. Proponents of various forms of interactionist perspectives include Philip Kitcher, who refers to his view as "causal democracy", and Susan Oyama, who describes her perspective as "constructive interactionism". Critics of interactionism include major figures in behavioral genetics such as Arthur Jensen, Robert Plomin, and philosopher Neven Sesardic.
Vantage sensitivity is a psychological concept related to environmental sensitivity, initially developed by Michael Pluess and Jay Belsky. It describes individual differences in response to positive experiences and supportive environmental influences. According to vantage sensitivity, people differ considerably in their sensitivity to positive aspects of the environment, with some people benefitting particularly strongly from positive experiences such as parental care, supportive relationships, and psychological interventions, whereas others tend to respond less or not at all.
Robert Keers was a British psychologist conducting innovative research on individual differences in mental health problems with a specific focus on psychiatric genetics.