How hand placement modulates interference from extraneous stimuli

Placing the hands around the position in which the relevant target letter for an Eriksen flanker task appears has been shown to reduce the interference produced by incompatible, irrelevant flanker letters presented outside of the hands. This result has been attributed to the hands providing an attentional window in the space between them, which results in enhanced processing of the stimulus within it. Alternatively, the hands may act as a reference frame relative to which attention can also be directed more effectively to the space outside of the hands. We conducted four experiments to test implications of the attention window and reference-frame accounts, using left and right foot-press responses. Although placing the hands around the inner letter reduced interference on flanker-incompatible trials, as previously found, it did so just as much when the letter outside of the hands was specified as the target and the letter between the hands was the distractor. Also, placement of wooden blocks around the inner letter reduced interference to a similar extent, again regardless of whether the inner or outer letter was designated as the target. These findings support the view that the reduction in flanker interference produced by placing the hands around the inner letter is due to their providing a reference frame relative to which visual attention can be directed either inside or outside.