It’s generally thought that interaction with humans tends to enhance animals’ skills in “reading” human signals. This study (link below) found another correlation to do with horses’ ability to solve tasks on their own; the more that horses appeared to be interested in humans, the worse they were observed to perform in an operant learning task. Of 46 horses tested, only 7 lived out with ad lib hay. The others were stabled and fed 3 times a day at most. It’s interesting to speculate on whether results might have differed if a greater proportion of the “participants” were in the first group, and a future study might usefully compare the two groups.