Vision is biased near handheld, but not remotely operated, tools

Action does not drive visual biases in peri-tool space

Observers experience visual biases in the area around handheld tools. These biases may occur when active use leads an observer to incorporate a tool into the body schema. However, the visual salience of a handheld tool may instead create an attentional prioritization that is not reliant on body-based representations. We investigated these competing explanations of near-tool visual biases in two experiments during which participants performed a target detection task. Targets could appear near or far from a tool positioned next to a display. In Experiment 1, participants showed facilitation in detecting targets that appeared near a simple handheld rake tool regardless of whether they first used the rake to retrieve objects, but participants who only viewed the tool without holding it were no faster to detect targets appearing near the rake than targets that appeared on the opposite side of the display. In a second experiment, participants who held a novel magnetic tool again showed a near-tool bias even when they refrained from using the tool. Taken together, these results suggest active use is unnecessary, but visual salience is not sufficient, to introduce visual biases in peri-tool space.

Rethinking Vision and Action

Action is an important arbitrator as to whether an individual or a species will survive. Yet, action has not been well integrated into the study of psychology. Action or motor behavior is a field apart. This is traditional science with its need for specialization. The sequence in a typical laboratory experiment of see → decide → act provides the rationale for broad disciplinary categorizations. With renewed interest in action itself, surprising and exciting anomalous findings at odds with this simplified caricature have emerged. They reveal a much more intimate coupling of vision and action, which we describe. In turn, this prompts us to identify and dwell on three pertinent theories deserving of greater notice.

Does response facilitation to visuo-tactile stimuli around a remote-controlled hand avatar reflect peripersonal space or attentional bias?

People react faster to visuo-tactile stimuli presented near the body (i.e., in peripersonal space) than to tactile stimuli presented alone. This multi-sensory facilitation effect has been used as a measurement of peripersonal space. Previous research has reported that peripersonal space representations can be modulated by actively using hand-held tools or disconnected hand avatars. However, previous research has ignored the possibility that the attentional effect of active tool use could affect multi-sensory facilitation. In the present study, we delivered tactile stimuli to participants' left or right hand concurrently with visual stimuli presented near a virtual hand avatar operated by the movements of participants' left or right hand, which was shown far in a virtual environment and disconnected from the body. Participants reacted to tactile stimuli while ignoring the visual stimuli. The results indicated a multi-sensory facilitation effect when tactile stimuli were delivered to the hand used to operate the hand avatar. In contrast, the facilitation was not observed when the tactile stimuli were delivered to the hand that is not operating the hand avatar. These results suggest that the strength of the multi-sensory facilitation effect differed across conditions, even though the visual attention captured around the hand avatar was controlled across conditions. We concluded that the modulation of peripersonal space resulting from using tools or avatars is nearly independent of visual attention captured around tools or avatars.