Under states of uncertainty, animals and humans show vigilance: a readiness for new or unexpected events. By contrast, in states of certainty, animals and humans can focus attention on central locations or activities. Vigilance in animals is typified by unfocused attention, faster orientation to stimuli, shorter visual fixations, and increased scanning. Modulation of states of attention involves the locus coeruleus, a brainstem nucleus that expresses norephinepherine (Ne), a neurotransmitter, to many other parts of the brain.
We examined whether this model can explain how infants look around an environment where unexpected things happen. Infants interacted with an adult in a testing room, and periodically one of six monitors around the room turned on and played a brief video. These unexpected events were expected to activate LC and draw out signs of vigilance. Infants’ looking responses were coded in detail for indices related to vigilance.
Three patterns of behavior were strongly correlated, as reported by de Barbaro, Chiba and Deák (2011):
- Latency to turn towards the video
- Total times infant looked at targets
- Average duration of non-target fixations
This is consistent with the hypothesis that individual infants were affected by Ne-modulation of attention. One implication is that short looking-times, which historically were related to infants’ intelligence, could also mean that infants are stressed out. Another implication is that infants who don’t act very social might be highly vigilant, because they are uncertain about the environment: infants who showed the greatest signs of vigilance were not attentive to the adult.