How does our visual system decide if something is a face? Some automated face-detecting software uses color as one cue that something is a face. For example Apple’s iPhoto has no trouble determining that there are two faces in this color picture:
That’s Nora in the back, and her cousin Ginger in front. In this picture, however, iPhoto can’t identify a face:
That’s a vintage black-and-white photo of Nora and Ginger’s grandfather, but the computer can’t find any faces in it. Do people, like computers, use color to help decide whether something they see is a face? Humans are excellent at identifying colors, and while faces can be many colors, there are also many colors that are very rarely seen in faces (e.g. blue, green, orange). Could we use skin-tones to help identify faces?
Markus Bindemann and Mike Burton created a set of images with faces placed in random locations, like this:
Some were full-color, some black-and-white, some had faces in black-and-white and color backgrounds, and some had black-and-white backgrounds and color faces. The faces also varied in size and position within the pictures. One-third of the photos contained no faces at all. Twenty-four volunteers watched as these images flashed in front of them, indicating as quickly as possible whether they saw a face. Did the color of the faces matter? Here are the results:
Color faces were detected significantly faster than black-and-white faces. Even when the black-and-white faces were on a color background, they were still detected significantly more slowly. Similarly, more errors were made on black-and-white faces compared to color faces.
In a second experiment, Bindemann and Burton showed viewers face pictures that were half-color and half- black-and-white, in addition to the normal full-color faces. Once again, full-color faces were detected significantly faster.
The researchers say this means the visual system must be searching for skin-colored areas of a roughly elliptical or oval shape–much like computers do.
Bindemann, M., & Burton, A.M. (2009). The Role of Color in Human Face Perception Cognitive Science, 33, 1144-1156 : 10.1111/j.1551-6709.2009.01035.x