Previous research on the interaction between manual action and visual perception has focused on discrete movements or static postures and discovered better performance near the hands (the near-hand effect). However, in everyday behaviors, the hands are usually moving continuously between possible targets. Therefore, the current study explored the effects of continuous hand motion on the allocation of visual attention. Eleven healthy adults performed a visual discrimination task during cyclical concealed hand movements underneath a display. Both the current hand position and its movement direction systematically contributed to participants' visual sensitivity. Discrimination performance increased substantially when the hand was distant from but moving toward the visual probe location (a far-hand effect). Implications of this novel observation are discussed.

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The current study explored effects of continuous hand motion on the allocation of visual attention. A concurrent paradigm was used to combine visually concealed continuous hand movements with an attentionally demanding letter discrimination task. The letter probe appeared contingent upon the moving right hand passing through one of six positions. Discrimination responses were then collected via a keyboard press with the static left hand. Both the right hand's position and its movement direction systematically contributed to participants' visual sensitivity. Discrimination performance increased substantially when the right hand was distant from, but moving toward the visual probe location (replicating the far-hand effect, Festman et al., 2013). However, this effect disappeared when the probe appeared close to the static left hand, supporting the view that static and dynamic features of both hands combine in modulating pragmatic maps of attention.

We studied the spreading of feature-based attention from attended to ignored motion fields (linear, circular, and combinations). When observers attended one of two superimposed motion fields on one side of the visual midline, sub-threshold priming by an ignored motion field was altered significantly on the opposite side of the midline. This attentional spreading was observed only when attended and ignored motion fields conformed to a complex global flow, not when they shared the same linear motion. These findings corroborate an earlier study (Festman & Braun, 2010), which obtained similar results with a complementary methodology. We conclude that feature-based attention is more complex than hitherto appreciated in that it spreads preferentially in an object-specific manner.

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