LAUSR

Sleep restriction and fatigue negatively impacts learning in adults, but the effect of fatigue on learning in infants remains unexplored. During their first two years infants frequently cycle through periods of wakefulness and sleep. Thus, infants often encounter new information in an unrested state. How might mild fatigue impact their attention and learning? Given that infants devote more attention to new learnable than new unlearnable patterns (Gerken et al, 2011) how might their physiological state impact the cognitive resources required to attend to and learn new information? We randomly assigned 80 17-month-old infants (Mage=17.06m, SD=1.85, Female=38) to a rested or unrested condition corresponding to their participation just after or before their typical nap. Within conditions, we randomly assigned infants to a learnable or unlearnable artificial language. We measured time to habituate over blocks of 4 trials that ended when total looking time over a fixed window of four trials reduced to less than 50% of total looking time across the prior four trials. We tested retention after a 5-minute delay in the learnable condition by measuring mean looking time for 8 trials with new grammatical stimuli vs. 8 trials with ungrammatical stimuli. Thus, we evaluated whether physiological state impacted 1) habituation during initial language exposure and 2) discrimination of grammatical vs. ungrammatical language structure, or learning. First, does state of fatigue impact infants’ attention to learnable vs. unlearnable stimuli? Infants attended longer to learnable than unlearnable stimuli regardless of physiological state (t(78)=2.043, p=.044, ML=175.77, MU=140.51). Second, does state affect learning? Fatigued infants discriminated grammatical from ungrammatical stimuli at test (MG=6.81s, MUG=8.24s; t(17)=-2.26, p=.037), but rested infants did not (MG=6.69s, MUG=6.59s, t(13)=.26, p=.80). Fatigue does not appear to impact infants’ ability to detect learnable information but may impact their ability to learn and retain that information. All infants eventually acquire their native language, but mild fatigue, whether reflecting an enhanced physiological or cognitive learning state, appears to contribute to more rapid learning.