We can identify "mystery faces" just 6 pixels wide!

How good are humans at identifying faces? Amazingly good, even with only a few sparse pixels' worth of information. Inspired by the research of Pawan Sinha, who had found that people can recognize faces using just 12 × 14 pixels' worth of information, we wondered if people can distinguish between faces and non-faces with even less information. So, last Friday, we asked CogDaily readers to try to identify faces as small as one-quarter the size of those used in Sinha's study: just 6 by 7 pixels. Readers rated 8 different photos in four different sizes ranging from 20 pixels wide to just 6 pixels. How'd they do?

Very well, thank you very much! Average accuracy was almost 90 percent, and only one photo, at the lowest resolution, troubled readers so much that they weren't significantly better than 50 percent accurate -- the level dictated by chance. Here's the picture:

Can you tell whether this is a face? I'll give the answer at the end of the post.

We showed readers one of two different versions of eight different photos -- four faces and four non-faces. We tried to find non-face pictures that were similar in complexity to the face pictures (I'll show you all the originals at the end so you can decided for yourself). The first task was simply to say whether or not the picture was a face. Then readers were asked to identify the photos in an open-ended response. Even in these open-ended responses, accuracy was impressive. For example, over 20 percent of respondents correctly identified this photo as either a church, cathedral, or Notre Dame:

An even larger number -- 23 percent -- successfully identified Napoleon Bonaparte from this picture, at an even lower 15-pixel resolution.

When the Napoleon picture was bumped to 20 pixels wide, over 50 percent could identify it:

One person even identified this 10-pixel photo as Sean Connery!

This study filled up so quickly that we decided to do a supplemental poll on Monday. Those results have been incorporated into the graph above, and they confirm what we learned from the Casual Fridays study: We are accurate at distinguishing faces from other similarly complex pictures, even at resolutions as low as 6 × 7 pixels. In case you took the test and are curious which pictures you saw, here they all are, along with the original on which each was based (each person only saw one version of each pictures, and the pictures were not necessarily displayed in this order):

The photo of Sean Connery on the left above is the only picture in the entire group that wasn't identified at levels above chance. Only 46.5 percent of respondents identified it as a face.