Faster than invalidly cued targets, 
indicating a main effect of Cue Validity, F(1,56) = 910.50, p < 0.001, 2 = 0.94. In addition, p the position of the hands influenced RTs, indicated by a main effect of Hand Position, F(1,56) = 4.33, p = 0.042, 2 = 0.07, p with Observers slower to detect BKM 120 cost targets on the Owners’ hands compared to off the hands. Critically, the strength of the cueing effect was independent of the position of the hands, as there was no interaction between Cue Validity and Hand Position, F(1,56) = 0.41, p = 0.525, 2 = 0.01. A post hoc analysis comparing pFrontiers in Psychology | www.frontiersin.orgMay 2015 | Volume 6 | ArticleTaylor et al.Joint attention for stimuli on the handsthe validity effect for the On Hands and No Hands conditions confirms that there was no difference between the cost to shifting attention on someone else’s hands versus when there were no hands near the display, t(56) = 0.64, p = 0.525, d = 0.12.DiscussionThis experiment was designed to test how a single set of hands is attended by two people. There were two possible, competing outcomes. One outcome would be that the hand-based effect on attention would transfer to an Tangeretin web Observer when a set of hands were jointly attended. This possibility, based on studies showing how joint action and joint attention can evoke a shared representation between two people, predicts that attention should treat jointly attended hands the same, regardless of who they belong to. In this case, we predicted that both Owner and Observer would show delayed orienting of attention to stimuli on the hands (as in Taylor and Witt, 2014). 
Alternatively, it may be that ownership of the hand is necessary for the hand-based effect on attention. There are approximately 14 billion hands on the planet, and they are all visually similar. One’s own two hands, however, can be willed to action and are therefore unique. Consequently, in terms of the present study, only the Owners might display delayed orienting of attention for stimuli on the hands. The results of this study support the second prediction. Orienting attention to stimuli on the hands is slow compared to orienting attention to stimuli that appear far from the hands, but only when appearing on one’s own hands. The results from the present experiment replicates the original effect described by Taylor and Witt (2014), where attention oriented more slowly to, from, or on the hands compared to near or far from the hands. Importantly, the present results also imply that the effect of slow attentional orienting on the hands depends on ownership of the hands. Simply put, it is not enough for stimuli to appear on hands. Those hands must be controllable. This caveat is reminiscent of recent work demonstrating the importance of action intentions on action-related perceptual biases. For example, stimuli beyond reach are perceived as closer when holding a tool that brings them within reach, but only when the perceiver intends to use the tool (Witt et al., 2005). In our study, the Owner is capable of using their hands, and intends to react to stimuli presented on them (although not with them), whereas the Observer cannot act with those hands–they are just objects in the world. However, it remains unclear when these effects of action on perception occur in observers (e.g., Bloesch et al., 2012; Witt et al., 2012, 2014), and when they do not. It bears mention that the present research used a localization task, whereas the Taylor and Witt (2014) p.Faster than invalidly cued targets, indicating a main effect of Cue Validity, F(1,56) = 910.50, p < 0.001, 2 = 0.94. In addition, p the position of the hands influenced RTs, indicated by a main effect of Hand Position, F(1,56) = 4.33, p = 0.042, 2 = 0.07, p with Observers slower to detect targets on the Owners' hands compared to off the hands. Critically, the strength of the cueing effect was independent of the position of the hands, as there was no interaction between Cue Validity and Hand Position, F(1,56) = 0.41, p = 0.525, 2 = 0.01. A post hoc analysis comparing pFrontiers in Psychology | www.frontiersin.orgMay 2015 | Volume 6 | ArticleTaylor et al.Joint attention for stimuli on the handsthe validity effect for the On Hands and No Hands conditions confirms that there was no difference between the cost to shifting attention on someone else's hands versus when there were no hands near the display, t(56) = 0.64, p = 0.525, d = 0.12.DiscussionThis experiment was designed to test how a single set of hands is attended by two people. There were two possible, competing outcomes. One outcome would be that the hand-based effect on attention would transfer to an Observer when a set of hands were jointly attended. This possibility, based on studies showing how joint action and joint attention can evoke a shared representation between two people, predicts that attention should treat jointly attended hands the same, regardless of who they belong to. In this case, we predicted that both Owner and Observer would show delayed orienting of attention to stimuli on the hands (as in Taylor and Witt, 2014). Alternatively, it may be that ownership of the hand is necessary for the hand-based effect on attention. There are approximately 14 billion hands on the planet, and they are all visually similar. One's own two hands, however, can be willed to action and are therefore unique. Consequently, in terms of the present study, only the Owners might display delayed orienting of attention for stimuli on the hands. The results of this study support the second prediction. Orienting attention to stimuli on the hands is slow compared to orienting attention to stimuli that appear far from the hands, but only when appearing on one's own hands. The results from the present experiment replicates the original effect described by Taylor and Witt (2014), where attention oriented more slowly to, from, or on the hands compared to near or far from the hands. Importantly, the present results also imply that the effect of slow attentional orienting on the hands depends on ownership of the hands. Simply put, it is not enough for stimuli to appear on hands. Those hands must be controllable. This caveat is reminiscent of recent work demonstrating the importance of action intentions on action-related perceptual biases. For example, stimuli beyond reach are perceived as closer when holding a tool that brings them within reach, but only when the perceiver intends to use the tool (Witt et al., 2005). In our study, the Owner is capable of using their hands, and intends to react to stimuli presented on them (although not with them), whereas the Observer cannot act with those hands--they are just objects in the world. However, it remains unclear when these effects of action on perception occur in observers (e.g., Bloesch et al., 2012; Witt et al., 2012, 2014), and when they do not. It bears mention that the present research used a localization task, whereas the Taylor and Witt (2014) p.