The startle reflex is an innate defensive reaction (Lang, 1995; Yeomans, Li, Scott, & Frankland, 2002), delegate to the instantaneous reaction following an unexpected and intense stimulus. The startle widely satisfies the requirements essential to be used as a research tool, since it is modified by the experience, it is easily and universally elicitable (Landis & Hunt, 1939), and its physical and temporal characteristics are well known and highly controllable (Costa & Ricci Bitti, 1998; Davis, Hitchcock, & Rosen, 1987). Yet, despite the importance of the study of this reflex in various research fields (from the study of motivational, emotional and attentive phenomena, to the investigation of neurological, neurophysiological and neuropsychological diseases; Balaban, 1996; Lang, 1995; Richards, 1998; Prechtl & Beintema, 1964), the startle modification is still relatively unexplored in early infancy. This lack in developmental psychological research is mainly due to two problems: the difficulty to identify and develop new methodologies suitable to explore the startle modification in early infancy; the intrusiveness and invasiveness of the commonly used measurement methodology, that is the eyeblink electromyography. Two experimental studies are presented in this dissertation. They were designed to explore the startle modification by using a new non-invasive methodology (AIMMSS) and a new experimental paradigm based on the use of infants facial expressions. In particular, the main indexes of positive (smile) and negative (distress) facial expressions were analysed using the most known anatomically based systems to coding the infants’ facial behaviour (Baby FACS, Oster, in press; AFFEX, Izard, Dougherty, & Hembree, 1983; MAX, Izard, 1979). The first study (N = 12) was aimed at analysing the affective modulation of the startle response elicited during the 5-month-old infants’ spontaneous exhibition of positive facial expressions (smile) and negative facial expressions (distress). The data obtained induce to hypothesize that the facial expressions act like a sort of motivational priming able to diversify, depending on their negative (distress) or positive (smile) nature, the intensity of the startle response elicited immediately after their exhibition. The second study (N = 26) was designed to analyse the modulatory influences exerted on the startle response by both the attentive state and the emotional state displayed by 3- and 5-month-old infants. The main result highlights that a synergy between the attentive and emotional systems cause the phenomenon of the affective modulation of the startle response.
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|Titolo:||Un nuovo approccio metodologico per l’indagine della modificazione del riflesso di trasalimento (startle) nei primi mesi di vita|
|Supervisori e coordinatori:||FABBRI, Paolo|
|Appare nelle tipologie:||10.2 Tesi di dottorato (EPrints)|