When using tools effects in body space and distant space often do not correspond. Findings so far demonstrated that in this case visual feedback has more impact on action control than proprioceptive feedback. The present study varies the dimensional overlap between visual and proprioceptive action effects and investigates its impact on aftereffects in motor responses. In two experiments participants perform linear hand movements on a covered digitizer tablet to produce ∩-shaped cursor trajectories on the display. The shape of hand motion and cursor motion (linear vs. curved) is dissimilar and therefore does not overlap. In one condition the length of hand amplitude and visual target distance is similar and constant while the length of the cursor path is dissimilar and varies. In another condition the length of the hand amplitude varies while the lengths of visual target distance (similar or dissimilar) and cursor path (dissimilar) are constant. First, we found that aftereffects depended on the relation between hand path length and visual target distance, and not on the relation between hand and cursor path length. Second, increasing contextual interference did not reveal larger aftereffects. Finally, data exploration demonstrated a considerable benefit from gain repetitions across trials when compared to gain switches. In conclusion, dimensional overlap between visual and proprioceptive action effects modulates human information processing in visually controlled actions. However, adjustment of the internal model seems to occur very fast for this kind of simple linear transformation, so that the impact of prior visual feedback is fleeting.

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In recent years, the interest and potential applications of pedestrian indoor navigation solutions have significantly increased. Whereas the majority of mobile indoor navigation aid solutions visualize navigational information on mobile screens, the present study investigates the effectiveness of a mobile projector-based navigation aid that directly projects navigational information into the environment. A benchmark evaluation of the mobile projector-based indoor navigation interface was carried out, investigating a combination of different navigation devices (mobile projector vs. mobile screen) and navigation information (map vs. arrow) as well as the impact of users' spatial abilities. Results showed the superiority of the mobile screen as a navigation aid and the map as a navigation information type. Especially users with low spatial abilities benefited from this combination in their navigation performance and acceptance. Potential application scenarios and design implications for novel indoor navigation interfaces are derived from our findings. RESEARCH HIGHLIGHTS • Experimental benchmark evaluation of a mobile pico projector for pedestrian navigation purposes. • Multidimensional evaluation of the effectiveness of navigation information for pedestrian navigation. • User experience and acceptance of mobile pico projectors. • Inclusion of cognitive user factors (e.g. spatial abilities) and user experiences (e.g. trust, privacy) of mobile navigation aid usage. • Outline of potential application scenarios and design implications for novel indoor navigation interfaces.

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