Converging evidence suggests that baseline pupil diameter is correlated with tonic levels of [[LC-NE system|LC-NE]] activity in rats, cats and monkeys<ref>Aston-Jones, G. & Cohen, J.D. An integrative theory of locus coeruleus–norepinephrine function: adaptive gain and optimal performance. Annu. Rev. Neurosci. 28, 403–450 (2005). </ref><ref>Koss, M.C. Pupillary dilation as an index of central nervous system α2-adrenoceptor activation. J. Pharmacol. Methods 15, 1–19 (1986). </ref>, as with human behaviors that are predicted to be associated with tonic LC-NE activity in a variety of experimental tasks and manipulations<ref>Gilzenrat, M.S., Nieuwenhuis, S., Jepma, M. & Cohen, J.D. Pupil diameter tracks changes in control state predicted by the adaptive gain theory of locus coeruleus function. Cogn. Affect. Behav. Neurosci. 10, 252–269 (2010).</ref><ref>Jepma, M. & Nieuwenhuis, S. Pupil diameter predicts changes in the exploration-exploitation trade-off: evidence for the adaptive gain theory. J. Cogn. Neurosci. 23, 1587–1596 (2011). </ref><ref>Einhäuser, W., Stout, J., Koch, C. & Carter, O.L. Pupil dilation reflects perceptual selection and predicts subsequent stability in perceptual rivalry. Proc. Natl. Acad. Sci. USA 105, 1704–1709 (2008).</ref><ref>Murphy, P.R., Robertson, I.H., Balsters, J.H. & O'Connell, R.G. Pupillometry and P3 index the locus coeruleus-noradrenergic arousal function in humans. Psychophysiology 48, 1532–1543 (2011). </ref>

[[File:Yarkes-Dodson arousal curve.png|500px|center]]

Oxitocin enhanced social detecting, and also pupil size (probably because of enhanced learning and attention)<ref>Siri Leknes, Johan Wessberg, Dan-Mikael Ellingsen, Olga Chelnokova1, Håkan Olausson and Bruno Laeng (2012) Oxytocin enhances pupil dilation and sensitivity to ‘hidden’ emotional expressions</ref>

==References==