Handedness and Graspability Modify Shifts of Visuospatial Attention to Near-Hand Objects

Abstract

We examined how factors related to the internal representation of the hands (handedness and grasping affordances) influence the distribution of visuospatial attention near the body. Left and right handed participants completed a covert visual cueing task, discriminating between two target shapes. In Experiment 1, participants responded with either their dominant or non-dominant hand. In Experiment 2, the non-responding hand was positioned below one of two target placeholders, aligned with the shoulder. In Experiment 3 the near-monitor hand was positioned under the placeholder in the opposite region of hemispace, crossed over the body midline. For Experiments 2 & 3, in blocked trials the palmar and back-of hand surfaces were directed towards the target placeholder such that targets appeared towards either the graspable or non-graspable space of the hand respectively. In Experiment 2, both left and right handers displayed larger accuracy cueing effects for targets near versus distant from the graspable space of the right hand. Right handers also displayed larger response time cueing effects for objects near the graspable versus non-graspable region of their dominant hand but not for their non-dominant hands. These effects were not evident for left-handers. In Experiment 3, for right handers, accuracy biases for near hand targets were still evident when the hand was crossed over the body midline, and reflected hand proximity but not functional orientation biases. These findings suggest that biased visuospatial attention enhances object identity discrimination near hands and that these effects are particularly enhanced for right-handers.

The Fragility of the Near-Hand Effect

“…In this study, performance on target detection without a cue (Study 2) was compared to target detection with a predictive peripheral cue in order to evaluate the potential contributions of the cue to the NHE and in order to evaluate the possibility that, in this task, a peripheral cue is necessary to instantiate the effect. The results of Reed et al (2006) would predict speeded responding near the hand regardless of cue validity, while a replication of other researchers would predict a larger cueing effect near the hand (Colman et al, 2017;Le Bigot & Grosjean, 2016;Lloyd et al, 2010). The present study employed a procedure matched to that used by Reed et al in order to determine whether a near hand has a cue-dependent or cue-independent effect on stimulus processing.…”

“…To investigate whether there was evidence for larger cueing effects near the hand (Colman et al, 2017;Le Bigot & Grosjean, 2016;Lloyd et al, 2010), an ANOVA was performed with cueing effect magnitude as the DV and position (lap/screen), non-responding hand (left/right), and target location (left/right) as the independent factors (Figure 9). This analysis produced no significant effects or interactions.…”

“…In addition, the use of geometric stimuli, which may not map cleanly onto the magnocellular and parvocellular pathways, limits the interpretation of this study (and, in principle, other studies as well e.g. Colman, Remington, & Kritikos, 2017;Lloyd et al, 2010;Weidler & Abrams, 2014). The subsequent studies therefore rely on target detection rather than discrimination paradigms, in order to more closely match early work studying the Near Hand Effect, setting aside the question of a potential visual pathway mechanism.…”

“…Reed et al (2006) employed a target-detection task and found that near-hand targets were detected more rapidly regardless of the validity of a predictive peripheral cue. In contrast, a number of researchers have employed target discrimination tasks and found that near-hands magnify the effect of the cue rather than causing a straightforward decrease in response time (Colman et al, 2017;Le Bigot & Grosjean, 2016;Lloyd et al, 2010). Since a visual cue is frequently used in NHE studies, but the evidence regarding the relationship between the NHE and cue presence is mixed, Study 3 directly investigated the relationship between cue presence and the NHE.…”

“…Furthermore, when cueing effects could be examined, the difference in cueing effect magnitude for hand-far minus hand-near conditions was calculated in the same manner (e.g. Colman et al, 2017;Le Bigot & Grosjean, 2016;Lloyd et al, 2010). These calculations produced indices of the Near Hand Effect in milliseconds ( Table 1).…”