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Background: Infants discover their social surroundings through visual and auditory input, which requires typical development of the attention networks. Alerting and social orienting as parts of these networks has been moderately explored in infancy. Method: Auditory stimuli (volume, social and nonsocial sounds and repetition) were manipulated to induce an arousal response, and the following pupil dilation and gaze behaviors were measured by pupillometry and eye tracking. Pupil dilation was used as an index of arousal in order to examine the potential relations between alerting, latency and social orienting in infancy. Pupil dilation, latency to any target, and target selection were measured over all presented sounds. These variables were assessed in the context of a so-called face pop out task, where infants tend to selectively attend to faces among distractors (social orienting) in a bottom-up process. The final sample consisted of 25 5-month-old and 26 10 month-old infants. Results: High volume caused significantly larger pupil dilation (arousal) than low volume. Latency of eye movements to any target was shorter over all conditions in 10-month-old infants compared to 5-month-olds. An interaction effect of repetition and volume was found, where in the first repetition, high volume led to more hits to target than low volume. In addition, a significant four-way interaction effect was found between repetition, qualitative aspects, physical aspects and age. Conclusions: The study supports the use of pupil dilation as a measure of alerting/arousal in invancy, as it tracks volume changes in the auditory stimulus. The link between pupil dilation and speed of eye movements could not be verified as reflecting similar neurological processes as in adults. Lastly, this study's results support intants' ability of facial recognition as an innate abiolity, and indicates that it is also in fast development between 5- and 10-months of age.