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. 2015 May 6;9:216. doi: 10.3389/fnhum.2015.00216

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Copyright © 2015 Whitwell, Ganel, Byrne and Goodale.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution and reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

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Tests for dissociation using peak grip aperture (PGA) and the slopes of the controls (“O”s) and of DF (“X”s) across the natural grasps with haptic feedback (G_H) and “real-time” pantomimed grasps (RPG) and tests for abnormality in DF’s slope across the G_H and RPG tasks. (A) Reduction in PGA between the G_H and RPG tasks. The solid vertical bar reflects the 95% confidence interval and indicates a significant reduction in PGA moving from G_H to RPG for the controls. As can be seen, DF showed a similar reduction in her overall PGA. (B) Slopes relating PGA to target size for the controls (“O”s) and for DF (“X”s) for the G_H and RPG tasks. Dashes indicate the mean slope for the controls. DF’s slopes differ significantly from zero and are within the normal range in both tasks. For illustration, we included (1) the mean slope for the controls (solid dash) along with DF’s slope (“X”) computed from data reported by Goodale et al. (1994b) for the delayed-pantomimed grasping task (DPG); and (2) the mean slope relating grip aperture to Efron block width for DF (open triangle) and for the controls (solid dash) across 4 studies (Goodale et al., 1991; Westwood et al., 2002; Whitwell et al., 2014a, in press) of DF’s manual (perceptual) estimates (ME) of Efron block width. Evidently, the DPG task has a far more detrimental impact on DF’s slope than does the RPG task. In fact, DF’s slope in the DPG task failed to differ from zero (p = 0.9). Interestingly, DF’s particularly poor slope for the DPG task resembles those that are typically observed when she performs ME task. A 95% confidence interval around the controls’ mean ME slopes can be used to compare DF’s mean ME slope across those same four studies. Clearly, DF’s mean ME slope falls well outside the normal range. A 95% confidence interval to compare her mean ME slope against zero failed to yield a significant difference (p = 0.09). (C) The controls slopes for the G_H and RPG tasks do not differ significantly and, critically, the difference in DF’s slope between the two tasks falls within the range of differences observed in the controls. Thus, when compared to the G_H task, the RPG task affected DF’s slopes no differently than it did the controls.