Exp Brain Res (2011) 211:531–545 DOI 10.1007/s00221-011-2625-z R E S E A R C H A R T I C L E Giving a helping hand: effects of joint attention on mental rotation of body parts Anne Bo¨ ckler • Gu¨ nther Knoblich • Natalie Sebanz Received: 1 November 2010 / Accepted: 4 March 2011 / Published online: 1 April 2011 The Author(s) 2011. This article is published with open access at Springerlink.com Abstract Research on joint attention has addressed both the effects of gaze following and the ability to share rep- resentations. It is largely unknown, however, whether sharing attention also affects the perceptual processing of jointly attended objects. This study tested whether attend- ing to stimuli with another person from opposite perspec- tives induces a tendency to adopt an allocentric rather than an egocentric reference frame. Pairs of participants per- formed a handedness task while individually or jointly attending to rotated hand stimuli from opposite sides. Results revealed a signiﬁcant ﬂattening of the performance rotation curve when participants attended jointly (experi- ment 1). The effect of joint attention was robust to manipulations of social interaction (cooperation versus competition, experiment 2), but was modulated by the extent to which an allocentric reference frame was primed (experiment 3). Thus, attending to objects together from opposite perspectives makes people adopt an allocentric rather than the default egocentric reference frame. Keywords Joint attention Mental rotation Mental imagery Egocentric reference frame Allocentric reference frame Introduction Engaging in joint attention is at the heart of social inter- action, be it learning about objects from others (Csibra and A. Bo¨ckler (&) G. Knoblich N. Sebanz Donders Institute for Brain, Cognition, & Behaviour, Centre for Cognition, Radboud University, P.O. Box 9104, 6500 HE Nijmegen, The Netherlands e-mail: A.Bockler@donders.ru.nl Gergely 2009), coordinating interpersonal actions (Clark and Krych 2004; Richardson and Dale 2005; Sebanz et al. 2006) or ﬁguring out what others have in mind (Baron- Cohen 1991). Two aspects of attending together have predominantly been addressed in previous research. First, research on gaze following has been concerned with bot- tom-up, perceptual inﬂuences of joint attention. It has been shown that other people’s gaze automatically draws our attention towards the attended to location, providing a perceptual beneﬁt for this location (Driver et al. 1999; Ristic et al. 2002; for a review, see Frischen et al. 2007). Second, joint-attention research has addressed the role of shared representations. During joint attention, a triadic relationship is formed, including the attendees, the attended object as well as the knowledge that the respective other is attending to the same object as oneself. Engaging in shared attention with others was found to enhance infants’ focus on relevant aspects of the environment (Striano et al. 2006) and is thought to play a crucial role in the development of imitation, social cognition and language (Barresi and Moore 1996; Hobson 2002; Tomasello et al. 2005). Only recently, studies have started to explore how shared attention inﬂuences perceptual processing in adults (Richardson et al. 2009), and in particular, how differences in perspective modulate perception. Does attending to an object from different perspectives inﬂuence how we per- ceive that object? Given that people normally process objects from their own perspective, within an egocentric reference frame (Klatzky 1998), another’s attention from a different perspective may induce a switch to an allocentric perspective, where objects can be more easily processed in relation to the other’s body. There are some indications in the literature that people spontaneously consult the perspective of others. In a series of experiments by Samson et al. (in press), participants 123