Does an assimilative illusion like the Delboeuf illusion occur in the human face? We investigated factors that might influence the perceived size of the eyes in a realistic face. Experiment 1 manipulated the position of the eyebrows (high or low), the presence/absence of eye shadow, and the viewing distance (0.6 m or 5 m), then measured the perceived eye size using a psychophysical method. The results showed that low eyebrows (i.e., closer to the eyes) make the eyes appear larger, suggesting that the assimilation of eyes into the eyebrows is stronger when the eye-eyebrow distance is shorter. The results also demonstrated that the application of eye shadow also makes the eyes look larger. Moreover, the effect of eye shadow is more pronounced when viewed from a distance. In order to investigate the mechanism of the eye size illusion demonstrated in Experiment 1, Experiment 2 measured the magnitude of the Delboeuf illusion at a viewing distance of 0.6 m or 5 m, with or without gray gradation simulating the eye shadow that was used in Experiment 1. The experiment demonstrated that the Delboeuf illusion is modulated by viewing distance and gradation in the same way as the eye size illusion. These results suggest that the eye size illusion induced by the eyebrows and the Delboeuf illusion involve the same mechanism, and that eye shadow causes the assimilation of the eyes into itself and enhances assimilation between the eyes and the eyebrows.

Groove is a pleasant feeling that compels people to move their bodies along with music. In the past, there was some consensus among both musicians and researchers that the main factor in inducing this feeling is onset asynchrony of sounds. However, recent studies have asserted that no-asynchrony is the condition that will obtain the highest groove. The current study examined whether no-asynchrony exclusively elicits the highest groove. In Experiment 1, we measured the groove increment of a backbeat drum pattern as a function of the asynchronies between bass guitar and hi-hat cymbal sounds. Upon evaluation, the scores of no conditions exceeded those of the synchronous condition. However, the condition with slight bass guitar precedence over the hi-hat achieved an approximately equal score to the condition with complete synchrony, and that score was higher than the ones achieved with bass delay. In Experiment 2, we measured the participants’ sensitivities to timing discrimination. The results confirmed that the amount of bass precedence in Experiment 1 was perceptible to the listeners. These findings suggest that complete synchronization is not always the best condition to achieve groove and that listeners prefer perceivable asynchronies in some cases.

Humans can envision the world from other people's viewpoints. To explore the embodied process of such spatial perspective taking, we examined whether action related to a whole-body movement modulates performance on spatial perspective-taking tasks. Results showed that when participants responded by putting their left/right foot or left/right hand forward, actions congruent with a movement's direction (clockwise/counterclockwise) reduced RTs relative to incongruent actions. In contrast, actions irrelevant to a movement (a left/right hand index-finger response) did not affect performance. Furthermore, we demonstrated that this response congruency effect cannot be explained by either spatial stimulus-response compatibility or sensorimotor interference. These results support the involvement of simulated whole-body movement in spatial perspective taking. Moreover, the findings revealed faster foot responses than hand responses during spatial perspective taking, whereas the opposite result was obtained during a simple orientation judgment task without spatial perspective taking. Overall, our findings highlight the important role of motor simulation in spatial perspective taking. (PsycINFO Database Record

Whereas geometric illusions in human faces have been reported by several studies, illusions of color or lightness in faces have seldom been explored. Here, we psychophysically investigated whether lip color influences facial skin's perceived lightness. Results of Experiment 1 demonstrated that redder lips lightened and darker lips darkened the perceived complexion. These lightness or darkness inducing effects differ from the classical illusion of lightness contrast in nonface objects for two reasons. First, illusory effects are more assimilative than contrastive. Second, the inducing area (i.e., lips) is much smaller than the influenced area (facial skin). Experiment 2 showed that the assimilative lightness induction was caused by holistic processing of faces. This is the first study to scientifically substantiate the claim of cosmetics manufacturers and makeup artists that lip colors can alter perceived facial skin color. Implications for face perception, lightness illusion, and perceptual effects of cosmetics are discussed.

We investigated whether the position of the eyebrows influences the perceived shape of the eyes by employing psychophysical measurements. Experiment 1 used arched and straight eyebrows at five different inclinations as stimuli and measured the perceived inclination of the eyes. The results demonstrated that the eyes are perceived to be somewhat inclined in the same direction as the eyebrows. Experiment 2 measured the perceived eye size by manipulating the distance between the eyes and the eyebrows and the curvature of the eyebrows across three levels. The results showed that the lower eyebrows (ie closer to eyes) made the eyes appear larger and the higher eyebrows made the eyes appear smaller, while eyebrow curvature had no effect on perceived eye size. Experiment 3 examined the role of the eye-eyebrow distance in the eye inclination illusion shown in experiment 1. The eye inclination illusion was unaffected by the eye-eyebrow distance, suggesting that the eye inclination illusion and the eye size illusion may involve different kinds of assimilation. These illusions are discussed in terms of face perception and possible practical applications.