Pupil Size Is a Marker of Intelligence
https://getpocket.com/explore/item/pupil-size-is-a-marker-of-intelligence
There is a surprising correlation between baseline pupil size and several measures of cognitive ability.
source URL: a Firefox start page story with many links to sources for further reading.
getpocket.com - seems not too spammy though looks like click-bait. lmk. usually don't notice them on new tabs