Abstract
van Lier and Koning introduced the more-or-less morphing face illusion: The detection of changes in a constantly morphing face-sequence is strongly suppressed by fast eye saccades triggered by a moving fixation dot. Modulators of this intriguing effect were investigated with systematically varied facial stimuli (e.g., human faces from varying morphological groups, emotional states) and fixation location. Results replicated the overall pattern of moving fixations substantially reducing the sensitivity to detect transitions. Importantly, a deviation from real to perceived changes could only be detected when faces were altered in a way not happening in real world—by changing identity. When emotional states of faces were changed, people were capable of perceiving these changes: A situation very similar to everyday life where we might quickly inspect a face by executing fast eye saccades but where we are still aware of transient changes of the emotional state of the very same person.
Highlights
Introduction van Lier andKoning (2014) provided with their more-or-less morphing face illusion yet more evidence that eye movements strongly impact our perception, here in terms of sensitivity of detecting ongoing changes in the background of a scene, that is, the nonfocused visual information
Results from this study showed that with a moving fixation dot, changes were perceived significantly smaller—or hardly noticed at all (M 1⁄4 1.19)—than with a stationary fixation dot between the eyes (M 1⁄4 2.85)
The initial graphical inspection of the data (Figure 4) shows the clear effect of much lower perceived morphing ranges when participants had to fixate on a moving fixation dot, which replicates the general finding of van Lier and Koning (2014)
Summary
Introduction van Lier andKoning (2014) provided with their more-or-less morphing face illusion yet more evidence that eye movements strongly impact our perception, here in terms of sensitivity of detecting ongoing changes in the background of a scene, that is, the nonfocused visual information. The authors showed quite impressively that as soon as beholders start fast eye saccades by following a to-be-fixated moving dot, the sensitivity to perceive changes within a sequence of animated transitions between two faces in the nonfocused area of a scene was substantially reduced. For their original experiment, they utilized artificially generated (FaceGen modeller!) basic faces (Face 1 to Face 7) which differed in their facial properties (e.g., position of eye brows). The main mechanism which was suggested to underlie the effect is a reduced sensitivity for transient signals during executing (fast) eye movements (e.g., van Lier & Koning, 2014). Van Lier and Koning (2014) further revealed an overestimation of the real morphing range when they had to fixate on a stationary fixation dot—they assumed that this overestimation happened as a result of a figural face aftereffect (Carbon & Ditye, 2011, 2012; Tangen et al, 2011; Webster & MacLin, 1999): through prolonged stationary fixation (between the eyes), differences in faces are perceived larger than they are
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