Project Title:
Longitudinal Twin Studies of Affective Style
(Project 4 of Affective Style Neural and Behavioral Substrates)
Principal Investigator:
H. Hill Goldsmith, PhD
This project has extended prior behavior-genetic research with infant twins to a
new sample of 250 pairs of 6-8 year-old twins, with the inclusion of measures to
provide a comprehensive assessment of physiology related to affective
reactivity, particularly anxiety. Physiological measures are obtained in the
laboratory under multiple baseline and emotion-elicitation conditions. The study
employs behavioral measures, assessed in the home, that allow us to assess the
latency, duration, and intensity of facial, vocal, and motoric responses to
affective stimuli. Other child and family characteristics are assessed by
interview and questionnaire, and medical histories are obtained. DNA samples are
stored for future analyses.
For the biological variables measured in this study, EEG asymmetry, basal and
reactive cortisol levels, fear-potentiated startle, and cardiac psychophysiology
(including impedance cardiography), there is often an implicit expectation that
individual variability will have at least a partial genetic basis. Prior studies
link these biological variables to behavioral measures of affective style and
particularly to aspects of inhibition. This project contributes to all four
types of evidence needed to complete the logical chain of inference involving
genetics, physiology, and behavior in this domain. First, a genetic basis for
behavioral individuality must be established. Next, a genetic basis for the
biological substrates (e.g., prefrontal EEG asymmetry) needs to be established.
Then, we investigate whether there is a common genetic basis for the
phenotypically associated behaviors and their biological substrates. Finally, as
the field advances, specific molecular genetic markers for relevant behavior and
physiology need to be identified.
Novel features of this twin study include its extensive protocol for salivary
cortisol collection and the inclusion of impedance cardiography so that a good
measure of the sympathetic contribution to cardiac reactivity can be extracted
and compared to parasympathetic tone (RSA). The project constitutes the most
comprehensive assessment of the central, autonomic and hormonal concomitants
related to affective style in young twins ever conducted.
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