Environmental Sensitivity: A Multi-Domain Investigation of its Development in Infancy

Highly sensitive individuals are thought to be disproportionately susceptible to both the risk engendering and development enhancing elements of their environment. If this is so, it seems necessary to hold that sensitivity is a unitary construct, in which markers of sensitivity to stimuli at neural, autonomic, and behavioural levels of analysis moderate the relationship between early social environments and outcomes, for better as well as for worse. The trait of environmental sensitivity (ES) is theorised, through conditional adaptation to enable resource exploitation or risk survival in the developmental context.
This thesis tests four main hypotheses: that measures of ES at different levels of analysis would covary at 6-months and would be evoked by positive and negative stimuli; whether associations between measures at 6-months would endure by 12-months; that indices of sensitivity at 12-months would associate with measures indexing the quality of the developmental environment; that measures indexing ES would moderate the relationship between the environment and outcomes. Neural, autonomic, and behavioural indices of ES were measured in N82 infants at 6-months and 12-months, while concurrently collecting data on the wellbeing and socioeconomic status (SES) of their parents. Levels of infant self-regulation and sustained attention were assessed at 12-months.
Associations between visual and auditory neural sensitivity were found at 6-months but not 12-months. Likewise, measures of positive and negative behavioural reactivity correlated at 6-months but not 12-months. Maternal SES moderated the relationship between negative reactivity at 6-months and positive reactivity at 12-months such that negatively reactive 6-months infants from high SES households were more positively reactive at 12-months. Baseline RSA at 6-months moderated the relationship between maternal anxiety and 12-months self-regulation but was marginally non-significant.
The results are interpreted from the perspective of theories and concepts that have been integrated into a single overarching meta framework of Environmental Sensitivity.