Human Temperament

Assessments of human temperament are difficult to develop due to the chronic cumulative interaction of both nature-nurture variables. From birth onward one’s temperament colors one’s current and future responses to stress. Inborn temperament shapes the manner in which patients respond to stress and is an integral part of later reported symptoms and behaviors. Medical professionals currently understand patient psychiatric and organic and functional symptoms within the context of cellular changes and alterations. Current psychopharmacological and immunopharmacological treatments focus on reversing the cellular response underlying these conditions and producing states of remission and relief of troubling physical symptoms. The impact of cumulative stress on cellular changes produced by stress-related genetic expression (the nature of which is determined by genetically predisposed temperament) has largely been overlooked in the research on the human being. As one examines temperament in the human being one needs to account for the influence of given genotype on different responses to stress over time.

Differences in temperament are apparent in an infant’s behavioral reactions to inoculation. Some neonates recover rather quickly from the distress of inoculation and others require external soothing (Gunnar et al., 2000). The variety of documented physiological measures i.e. alterations in heart rate, vagal tone and salivary cortisol, support the reported diversity in neonatal behavioral responses to vaccination (Gunnar et al., 1995). This diversity of response is reflective of differences in temperament. Some infants respond with a great deal of crying and present low levels of salivary cortisol, while others don’t fuss much, but yet present high levels of salivary cortisol (Lewis et al., 1993; Lewis & Ramsay, 1995). Those infants and toddlers that achieve self-recognition (identifying oneself in a mirror with a streak of make-up on the nose) from ages 6 to 18 months tend to present greater reactivity to environmental interactions and stressors along with increased salivary cortisol levels (Lewis & Ramsay, 1997). Neonatal responsivity to stress can be further broken down into threshold for discomfort (how quickly or intensely is discomfort experienced), dampening (the nature of one’s ability to stop oneself from reacting to discomfort), and reactivivity (one’s tendency to repeat arousal to a stimulus) (Lewis, 1992). According to Michael Lewis (1992) there are four different types of infants that can be differentiated based on their sensory response to discomfort and their behavioral reactivity to discomfort. Easy children have a high threshold and a high dampening ability. They do not easily rouse and recover rather easily and quickly from stress. Easy children are most notably known as resilient. They are perceived by caregivers as more active and sociable. They are spontaneously able to elicit and receive lots of attention, are independent during play, and quickly learn required tasks with proficiency. Resilient adolescents tend to be less reactive to cumulative stressors experienced during family interactions (Werner & Smith, 1992). Low-reactive children have a high threshold for discomfort but have little dampening ability (i.e. they have difficulty cooling down their responses to distress on their own). High-reactive children have a low threshold and are highly sensitive for perceiving stress and discomfort but yet have a high dampening ability (i.e. they can easily and quickly recover from their responses to stress on their own). Difficult children have low thresholds for stress (i.e. they are very sensitive and easily reactive to stressful conditions) and little dampening ability (i.e. they have difficulty in cooling down their responses to stress on their own). A difficult child is more apt to be labeled conduct disordered, truant, juvenile offender, and a school drop out (Fergusson & Lynskey, 1996). The difficult child is also more apt to engage in novelty seeking, an aspect of temperament where an individual seeks out new experiences to fill an emotional void or to sooth from chronic and persistent emotional pain. Differences in activity level, rhythmicity, approach/withdrawal, adaptability, intensity of reaction, response threshold, intensity and duration of mood, attention span, and distractibility are all temperament characteristics that are evident as early as birth and color an individual’s later responses in interaction throughout one’s life span (Soderman, 1986)

That inborn temperament provides a template as to how one will respond to environmental stressors is clearly demonstrated in studies that monitor monzygotic twins raised apart. Identical twins share similar affective symptoms in response to stress (e.g. anxiety, panic symptoms, obsessive-compulsive symptoms, or depressive symptoms) (Torgersen, 1990). The intensity of affective symptoms and the extent that they can lead to physical illness (noted in subsequent sections of this web site) are linked to the individual’s intensity of response to prior cumulative and present stressors.

Depressed mothers give birth and raise offspring. As they raise their children they interact in certain ways. Depressed mothers often avoid direct interacting with their infants by avoiding eye contact and tend to be more critical of their infants and toddlers in interaction than healthy mothers in interaction with their offspring. The infant receives eye avoidance from depressed mother and responds in “gaze aversion” that causes the infant to look away from mother and to disengage attention from her. Physiological measures associated with interactive avoidance in these infants also demonstrate greater right frontal electroencephalographic (EEG) activation (Field et al., 1995), lower vagal tone, and elevated plasma norepinephrine, epinephrine, and dopamine levels and salivary cortisol levels at 3 and 6 months of age (Field et al., 2000). These infants as toddlers also present greater distress with separation and negative emotion along with behavioral inflexibility during play, daily interactions, and stressful situations with peers and with mother (Field et al., 1987; Field, 1994). Depressed mothers tend to interact with their offspring in a similar way that Dr. Meaney’s low LG-ABN mothers parented their offspring in section 1.22. “Good enough” rat and human maternal behaviors both produce greater stress arousal in respective offspring. In the same way that Meaney and colleagues encouraged mothering rats to be more effective nurturers during earlier handling experiments, Tiffany Field and colleagues helped depressed human mothers to enhance their interactions with their infants. They (Field, 1987; Pelaez-Nogueras et al., 1996; Field et al., 2000) developed nurturing programs that encouraged depressed mothers to increase their touching stimulation of their infants and to establish eye contact and imitate their infant’s facial responses in their interactions with their infants. Both modifications were sufficient to improve interaction between mother and infant. Benefits to respective infants included reductions in infant’s right frontal EEG, decreases in circulating catecholamine concentrations and salivary cortisol levels, increases infant attentiveness, reductions in gaze aversion, as well as increases in infant behavioral flexibility during interaction. Another study demonstrated that a 30 month old’s ability to refrain from touching an attractive toy was highly correlated with developmentally sensitive maternal distraction that reallocated the toddler’s attention away from the desired toy (Putnam et al., 2002). Infants seem to positively respond to developmentally sensitive maternal behaviors by reducing physiological indicators and enhancing behavioral resiliency.

The long-term effects of positive changes in mother-child interactions on the infant’s later personality development and in the later development of maternal behaviors and the overall long-term effectiveness of the above-noted programs were not monitored. Prospective research of this sort is sorely needed (Erlenmeyer-Kimling, 1979) to help both neuroscience and psychotherapy communities to understand how deficits in nurture modulate an organism’s later chronic stress response and how maternal nurturing improvements can prevent this process. The quality and impact of early nurture becomes the later adult nature (manifested in psychological and physical symptoms) that requires later psychopharmacological treatment.

In summary, maternal behaviors that do not meet offspring need for nurture stimulate infant neurobiological stress-related neurocircuitry and neurohormone release and secretion. The exact nature of the stress neurocircuitry and neurohormone release is genetically predetermined and passed on from one generation to another and is evidenced in the nature of temperament. Chronic and persistent stress may allow for the genetic expression of neurocircuitry and neurohormone response that underlies the later development of affective symptoms to stress and cognitive impairments by, according to Meaney and colleagues, altering receptor expression in discrete regions of the brain, like the hippocampus. Genes are ready and awaiting expression; stressful family interactions are the variables that stimulate and allow for their future expression.

References

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Soderman AK (1986): Dealing with difficult young children. In: Reducing Stress in Young Children”#x2019;s Lives. Ed.: J Brown McCracken, pp. 116-121, National Association for the Education of Young Children, Washington D.C.

Torgersen S (1990): Genetics of anxiety and its clinical implications. In: The Neurobiology of Anxiety-Handbook of Anxiety-Volume 3. Eds.: GD Burrows, SM Roth, R Noyes, pp. 381-405, Elsevier, Amsterdam, Netherlands.

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