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 )