A person’s ability to recognize a whole face is not any better than his ability to recognize an individual feature, say researchers from Indiana University and the University of California, Los Angeles.
Traditionally, scientists have believed that humans look at faces holistically — visually combining the eyes, nose, mouth — and that by perceiving the relationships among them, we have an advantage over viewing each feature individually.
“Surprisingly, the whole was not greater than the sum of its parts,” says Jason M. Gold of Indiana University.
For the study, researchers used a theoretical model called an “optimal Bayesian integrator” (OBI). The OBI evaluates how well a person perceives a series of information — in this case, facial features — and merges all of the information together as though the person was perceiving each feature one by one.
A score was given based on how well the person recognized the combination of features (the whole face), and it should have equaled the sum of the individual-feature scores. If the whole-face score exceeded this sum, it suggested that the relationship among the features proved to be the strongest—in other words, ‘holistic’ facial recognition exists.
In the first experiment, volunteers viewed fuzzy images of three male and three female faces. Then they viewed either one feature — a left or right eye, nose, or mouth — or all four in standard face-like symmetry appeared on the screen. That image would disappear and, if they saw an eye, six eyes would appear; if a whole face, six whole faces. The volunteers then chose the feature or face they’d just seen.
In the next experiment, the whole-face images were superimposed on face-shaped ovals. In both experiments, performance with the whole faces was not any better than with isolated features, and no better than the OBI. This suggests that the facial features were not processed holistically when shown in combination.
“The OBI offers a clearly defined mathematical framework for studying what historically has been a rather loosely defined set of concepts,” says Gold.
The results may help researchers understand the cognitive disorder prosopagnosia, an inability to recognize faces, and could also help in developing better face-recognition security software. But the real value, says Gold, is in basic research.
“If you want to understand the complexities of the human mind, then understanding the basic processes that underlie how we perceive patterns and objects is an important part of that puzzle.”
The research appears in the journal Psychological Science.