If you want more people to "like" your photos in Instagram, put your face in it.
Researchers at the Georgia Institute of Technology and Yahoo Labs checked out 1.1 million photos on Instagram, and found that pictures that included a human face — selfie or otherwise — are 38% more likely to get "likes" than pictures without any faces.
Pictures with faces are also 32% more likely to get a comments.
"The more you post, the less feedback you're going to get," said Saeideh Bakhshi, the Georgia Tech College of Computing doctorate student who led the study, in a post on Georgia Tech's site about the study. "Posting too much decreases likes two times faster than comments."
The researches used face-detection software to scan the photos.
They also found that the more photos a person uploads, the lower the probability that any single picture will get likes or comments. So don't start batch uploading a bunch of pictures in order to get more likes. It probably won't work.