Laterality effects in the spinning dancer illusion: The viewing‐from‐above bias is only part of the story

Abstract

The 'silhouette illusion', representing the silhouette of a female dancer pirouetting about her vertical axis, is a bistable stimulus created by Japanese web designer Nobuyuki Kayahara. Although the dancer can be perceived as spinning either clockwise or counterclockwise, the clockwise rotation is usually preferred. Troje and McAdam (i-Perception, 2010, 1, 143) showed that this clockwise bias can be attributed to the tendency to assume a viewpoint from above rather than from below, given that the dancer is portrayed from a vantage point that is not perpendicular to the axis of rotation. Here, we tested whether another possible factor contributing to the observers' interpretation of this bistable stimulus might be the tendency to perceive movements of the right rather than the left foot. We confirmed both the viewing-from-above bias and our hypothesis. The bias to perceive movements of the right leg might be a generalization to lower limbs of a perceptual frequency effect already observed for upper limbs. Such a perceptual and attentional bias towards the right hand/foot could account for the greater ability to predict the outcome of sport actions when observing right- rather than left-limbed movements, and thus the left-handers' and left-footers' advantage observed in a variety of interactive sports.

Inversion Reveals Perceptual Asymmetries in the Configural Processing of Human Body

“…Indeed, inversion, which is known to disrupt the configural processing of human bodies (e.g., Reed et al, 2003, 2006), abolished the bias to perceive right-handed actions found in the upright session. As predicted, and in line with our previous findings showing that the bias toward the right limb of human bodies is consistent across different types of stimuli and response modalities (Marzoli et al, 2015; Lucafò et al, 2016), the effect of session did not differ across the different tasks, which supports the robustness of our results. Our study thus provides an additional instance of the detrimental effects of body inversion on configural processing, such as reduction in perceptual grouping (Poljac et al, 2011, 2012), body posture recognition (Reed et al, 2003, 2006), action recognition (Dittrich, 1993) and emotion recognition from whole-body gestures and dance movements (Dittrich et al, 1996; Atkinson et al, 2007), as well as the abolishment of expertise-related advantage in action discrimination (Calvo-Merino et al, 2010).…”

“…This expedient was aimed at reducing the possible carry-over of responses from trial to trial (e.g., see Liu et al, 2012, who found percept carry-over even after a 30 s break between the presentation of an ambiguous spinning body and the next one). As in a previous study with the spinning dancer illusion (Lucafò et al, 2016), we decided to collect participants’ responses by means of two colored arrows, each representing a possible spinning direction, rather than by means of simple vocal responses such as “ORARIO” (the Italian word for “CLOCKWISE”) and “ANTIORARIO” (“COUNTERCLOCKWISE”), because the latter response modality seems to be rather troublesome for participants (maybe due to their difficulty in labeling as clockwise or counterclockwise a rotation about an axis approximately parallel to their own body axis). Before the task, in order to familiarize participants with the response modality, they were administered a pretest in which they had to use the two response arrows to indicate the spinning direction of a black human silhouette containing perspective cues (e.g., the relative size of the hands in different positions).…”

“…In a recent study, we found that when required to indicate the orientation (front or back view) of pictures of ambiguous human silhouettes performing one-handed manual actions, both right- and left-handers perceived the figures more frequently in an orientation congruent with a movement performed with the right rather than the left hand (Marzoli et al, 2015; see Lucafò et al, 2016 for consistent results for foot actions). This result suggests the presence in both right- and left-handers of a perceptual and attentional bias toward the right side of others’ body, and is in line with several studies dealing with the perception of sport actions, indicating that the outcomes of movements performed by right-handed or right-footed individuals are anticipated better than those of movements performed by left-handed or left-footed individuals (McMorris and Colenso, 1996; Hagemann, 2009; Loffing et al, 2012; Schorer et al, 2012).…”

“…We believe that any conclusion about the effects of inversion on the bias toward the right side of human bodies would be strengthened if results can be generalized across different types of stimuli. Given that our previous studies (Marzoli et al, 2015; Lucafò et al, 2016) indicate that such a bias is comparable across different types of stimuli and response modalities, we predicted that inversion effects would have been similar in the different tasks.…”

“…In the second task, we used stimuli that required the same response (perceived front or back view) as those in the first task, but that were physically different (dynamic point-light figures). In the third task, we used stimuli that required a different response (perceived clockwise or counterclockwise rotation) and that were physically different (rotating ambiguous silhouettes), but for which we could nonetheless expect a bias toward the right limb on the basis of our previous study with the spinning dancer illusion (Lucafò et al, 2016). We believe that any conclusion about the effects of inversion on the bias toward the right side of human bodies would be strengthened if results can be generalized across different types of stimuli.…”