The mark had gained specific value in pigeons because it had been associated with reward previously. With humans and great apes, the mark was lacking associations with rewards. And as my link says: Not een apes really do self-recognize.
8:26 AM - 23 Dec 2017
0 replies
1 retweet
0 likes
Loading seems to be taking a while.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.