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Researchers have found that several species, including humans, dilate their pupils when they experience sensations which capture their attention, called pupil orienting response. Little is known about how this presents in early development. We studied this phenomenon in 5-month old infants. In addition, we explored how the orienting response changes after repeated exposure to the same stimuli. Participants were shown a video of a face moving around on a 2D plane, during which sound played either before (asynchronous condition) or during (synchronous condition) a shift in the face's movement direction. Pupil dilation increase lasted longer in the asynchronous condition compared to the synchronous condition. A post-hoc analysis showed that pupil dilation decreased over repeated audio-visual exposures only in the synchronous condition, an indication of habituation occurring only when audio and visual change occur simultaneously. The limitations of our current paradigm indicate improvements that can be made in future studies. Our results provide additional information about differences in sensory processing in infants, and extend into new possible avenues of studying attention in early development.