Please cite this article in press as: Costantini, M., et al. Tool-use observation makes far objects ready-to-hand. Neuropsychologia (2011), doi:10.1016/j.neuropsychologia.2011.05.013 ARTICLE IN PRESS G Model NSY 4142 1–6 Neuropsychologia xxx (2011) xxx–xxx 1 Contents lists available at ScienceDirect Neuropsychologia jo u r n al hom epage : www.elsevier.com/locate/neuropsychologia Tool-use observation makes far objects ready-to-hand 1 Marcello Costantini a,∗ , Ettore Ambrosini a , Corrado Sinigaglia b , Vittorio Gallese c,d 2 a Laboratory of Neuropsychology and Cognitive Neuroscience, Department of Neuroscience and Imaging, University G. d’Annunzio, Chieti-Pescara, Italy & ITAB Institute for Advanced Biomedical Technologies, Foundation University G. d’Annunzio, Via dei Vestini 33, 66013 Chieti, Italy 3 4 b Department of Philosophy, University of Milan, Italy 5 c Department of Neuroscience, University of Parma, Italy 6 d IIT (Italian Institute of Technology) Brain Center for Social and Motor Cognition, Parma, Italy 7 8 a r t i c l e i n f o 9 10 Article history: 11 Received 28 February 2011 12 Received in revised form 12 May 2011 13 Accepted 18 May 2011 14 Available online xxx 15 Keywords: 16 Peripersonal space 17 Tool-use 18 Action observation 19 a b s t r a c t Previous evidence has shown that active tool-use remaps agents’ reaching space with far objects being perceived as reachable and graspable. To date, however, there is no evidence that tool-use observation might also be effective in reaching space remapping. The present six experiments show that not only performing but also observing tool actions may extend the representation of reaching space, useful for grasping objects. In addition, like active tool-use, tool-use observation also impacts on visual distance judgment. Interestingly, these effects only occurred when observers shared the same action potentialities with the agent, i.e., while passively holding a tool compatible with the goal and the spatial range of the observed action. The present findings demonstrate that observing someone else acting with a tool may actually shape the way we map the objects and the space around us, suggesting that such a mapping could provide us with a keystone for coordinating and integrating our actions with those of others. © 2011 Published by Elsevier Ltd. 1. Introduction 20 Tool use may extend our action space by making out-of-reach 21 objects reachable. Often, we use tools alone, but it is not uncommon 22 for us to need to coordinate our tool actions with those of another 23 individual in order to reach for and grasp a common target. In this 24 case it is necessary to tune our own tool use with that of the other, 25 by matching executed with observed actions in terms of both their 26 motor goals and their spatial range. 27 There is converging evidence from neurophysiological, neu- 28 ropsychological and behavioral studies that active tool-use deeply 29 impact on agents’ space representation, extending their own reach- 30 ing space according to the range of tool action. In their seminal 31 studies, Iriki, Tanaka, and Iwamura (1996) (Ishibashi, Hihara, & Iriki, 32 2000) showed that the visual receptive fields of monkey’s parietal 33 neurons can be modified by actions involving tool use. They trained 34 monkeys to retrieve pieces of food with a small rake, and found 35 that, when the instrument was used repeatedly, the visual recep- 36 tive fields (vRFs) anchored to the hand expanded to encompass the 37 space around both the hand and the rake. If the animal continued 38 to hold the rake, but stopped using it, the vRFs shrank back to their 39 normal extension. 40 ∗ Corresponding author. Tel.: +39 0871 3556945; fax: +39 0871 3556930. E-mail address: marcello.costantini@unich.it (M. Costantini). The dynamic mapping of peripersonal space has been also 41 demonstrated at the behavioral level in both healthy (Maravita, 42 Spence, Kennett, & Driver, 2002; Serino, Bassolino, Farne, & Ladavas, 43 2007) and brain damaged humans. Line-bisection studies on 44 patients with selective neglect for the hemi-space close to (or far 45 from) their body showed that tool use might reduce or increase the 46 neglect according to the status of the line to be bisected (reach- 47 able or out-of-reach) in relation to tool use (Ackroyd, Riddoch, 48 Humphreys, Nightingale, & Townsend, 2002; Berti & Frassinetti, 49 2000; Neppi-Modona et al., 2007; Pegna et al., 2001). Similar results 50 have been found in patients with visuo-tactile extinction selec- 51 tively confined to the space close to one hand. Several studies have 52 shown that the severity of extinction can be modified by tool use, 53 which extends the reach of hand actions (Farnè & Ladavas, 2000; 54 Farne, Iriki, & Ladavas, 2005; Maravita, Husain, Clarke, & Driver, 55 2001). 56 To date, however, there is no evidence on the impact of 57 tool-use observation on the observers’ action, particularly on the 58 space representation they should recruit when actively performing 59 reach-to-grasp movements. The above-reviewed studies demon- 60 strate that passive tool holding does not have any effect on the 61 reaching space of an individual. But what happens if the passive 62 tool holder were observing someone else using that same tool? 63 Previous studies (Cardellicchio, Sinigaglia, & Costantini, 2011; 64 Costantini, Ambrosini, Tieri, Sinigaglia, & Committeri, 2010) have 65 shown that the perception of object-related or micro-affordances 66 (such as a mug with handle, Ellis & Tucker, 2000) is spatially 67 0028-3932/$ – see front matter © 2011 Published by Elsevier Ltd. doi:10.1016/j.neuropsychologia.2011.05.013