The exchange of emotional information through facial expressions is essential to early infant-caregiver interaction. The ability to process and comprehend information from facially communicated emotional signals develops significantly throughout the first year of life. One manifestation of this development during the second half of the first year is infants? increased attention to fearful rather than happy and emotionally neutral facial expressions. The four studies reported in this dissertation were intended to characterize the emotional modulation of attention in further detail by investigating the developmental emergence of and the critical factors underlying the attentional prioritization of fearful expressions in infancy.

Study I reported evidence of the emergence of enhanced attention to fearful faces between 5 and 7 months. While the data from 7-month-old infants replicated earlier findings of longer looking and larger attention-sensitive brain responses to fearful than happy faces, no differences were observed with either measure in 5-month-old infants. Studies II-IV utilized a novel paradigm to examine 7-month-old infants´ disengagement of attention from facial expression stimuli toward non-emotional distractor stimuli and the critical factors that may underlie infants´ attentional bias to fearful faces. These studies showed that fearful faces modulate infants´ attention disengagement by increasing the latency and decreasing the frequency of eye movements from the centrally presented face toward the peripheral distractor stimulus. This effect was absent for faces that had been rated as novel as a fearful expression but lacking equal emotional signal value (Study II) and for neutral faces that had fearful eyes (Study III), the most prominent visual feature of a fearful expression. Finally, in Study IV, infants showed a larger deceleration of heart rate orienting response to fearful faces, resembling the autonomic response to threat-related stimuli typically observed in adults.

In light of these data, it is suggested that the turn of the second half of the first year is a period during which critical developmental changes take place in the way infants perceive, experience, and learn fear. At a developmental phase during which infants typically begin to move independently, emotional significance of sensory stimuli becomes integrated with the functioning of attentional control mechanisms. The persistent bias to prefer fearful expressions over other stimuli presumably enables relatively efficient associative learning about the contexts in which fearful emotions are expressed by the caregivers (e.g., situations involving impending danger). In terms of brain function, the development of emotion-attention interactions may reflect the emergence of functional connections between structures sensitive to the emotional significance of sensory stimuli (amygdala) and cortical areas implicated in attentional control and emotion regulation (prefrontal, orbitofrotal, and anterior cingulate cortices).