The Inverted-face Effect

Overview

Source: Laboratory of Jonathan Flombaum—Johns Hopkins University

In perception, it is often the case that the ability to recognize and interpret complex stimuli feels effortless but actually demands complicated and intensive processing. This is because processing is specialized and automated for certain types of very important stimuli. Among the best examples of this phenomenon is face processing. People do not try to detect and recognize faces. It just seems to happen. However, detecting faces and telling them apart from one another is actually a demanding computational task.

Human facial recognition abilities rely on specialized computations and dedicated brain networks. One simple demonstration of this is the inverted-face effect. Recognizing upside-down faces is far more difficult than recognizing them right-side up, but the same is not true for many other kinds of visual objects. The inverted-face effect is demonstrated in a variety of ways. This video shows an incidental encoding memory paradigm for investigating facial processing and the inverted-face effect.

Procedure

1. Equipment and Stimuli

This experiment requires a computer and experiment scripting software.
In addition, the experiment requires a relatively large set of facial images, preferably with similar lighting conditions and without emotional expressions. Many databases of such images are available freely online for research purposes. A good resource is the MIT face database: http://web.mit.edu/emeyers/www/face_databases.html#oulu

2. Design

Assemble a set

Results

To analyze the results, simply compute the proportion of faces correctly identified by the participant in trials with upside-down (inverted) and trials with right-side up (upright) faces. Compare performance using a bar graph, as shown in Figure 2. For most visually normal observers, accuracy will be much higher with upright compared to inverted faces. However, this is a difficult task, and you may find performance below 0.9 even for upright faces. For inverted faces, performance may even approach chance

Application and Summary

The discovery that inverted faces are difficult to process has many applications. Neuroimaging studies, for example, have taken advantage of the effect to identify brain regions involved in specialized face processing. Brain scans are taken when observers view upright as well as inverted faces. The responses to the two kinds of stimuli are then compared. Both sets of stimuli have very similar visual properties overall, leading to similar activity throughout much of the visual system. In one brain area though, upright fac