http://www.unz.com/jthompson/the-secret-in-your-eyes/

in a simple memory span task, pupil size precisely tracks changes in memory load, '''dilating with each new item held in memory and constricting as each item is [...] recalled '''
High`` ``working`` ``memory`` ``subjects’`` ``pupil`` ``diameters`` ``were`` ``0.97`` ``millimeter`` ``larger than those with low WMC, 
'''Working memory explained 6% of the variance '''in baseline pupil size and with each 1 SD increase in WMC there was a 0.30 mm increase in baseline pupil diameter, b = 0.30, r = 0.24. Fluid`` ``intelligence`` ``explained`` ``12%`` ``of`` ``the`` ``variance`` ``in`` ``baseline`` ``pupil`` ``size and each 1 SD increase in Gf was associated with a 0.45 mm increase in baseline pupil diameter, 

Additionally, the nice phrase “All grist to the mill.” = All things are a potential source of profit or advantage. ( http://www.phrases.org.uk/meanings/grist-to-the-mill.html )