Elena Carbone

Saccadic eye movements in a high-speed bimanual stacking task: changes of attentional control during learning and automatization.

Principles of saccadic eye movement control in the real world have been derived by the study of self-paced well-known tasks such as sandwich or tea making. Little is known whether these principles generalize to high-speed sensorimotor tasks and how they are affected by learning and automatization. In the present study, right-handers practiced the speed-stacking task in 14 consecutive daily training sessions, while their eye movements were recorded. Speed stacking is a high-speed sensorimotor task that requires grasping, moving, rotating, and placing of objects. The following main results emerged. Throughout practice, the eyes led the hands, displayed by a positive eye-hand time span. Moreover, visual information was gathered for the subsequent manual sub-action, displayed by a positive eye-hand unit span. With automatization, the eye-hand time span became shorter, yet it increased when corrected by the decreasing trial duration. In addition, fixations were mainly allocated to the goal positions of the right hand or objects in the right hand. The number of fixations decreased while the fixation rate remained constant. Importantly, all participants fixated on the same task-relevant locations in a similar scan path across training days, revealing a long-term memory-based mode of attention control after automatization of a high-speed sensorimotor task.

Saccadic eye movements in the dark while performing an automatized sequential high-speed sensorimotor task

Saccades during object-related everyday tasks select visual information to guide hand movements. Nevertheless, humans can perform such a task in the dark provided it was automatized beforehand. It is largely unknown whether and how saccades are executed in this case. Recently, a long-term memory (LTM)-based direct control mode of attention during the execution of well-learned sensorimotor tasks, which predicts task-relevant saccades in the dark, was proposed (R. M. Foerster, E. Carbone, H. Koesling, & W. X. Schneider, 2011). In the present study, participants performed an automatized speed-stacking task in the dark and in the light while their eye movements were recorded. Speed stacking is a sequential high-speed sensorimotor object manipulation task. Results demonstrated that participants indeed made systematic eye movements in the dark. Saccadic scan paths and the number of fixations were highly similar across illumination conditions, while fixation rates were lower and fixation durations were longer in the dark. Importantly, the eye reached a location ahead of the hands even in the dark. Finally, neither eye-hand dynamics nor saccade accuracy correlated with hand movement durations in the dark. Results support the hypothesis of an LTM-based mode of attention selection during the execution of automatized sequential high-speed sensorimotor tasks.

Investigating the contribution of metacontrast to the Fröhlich effect for size

According to the Fröhlich effect, observers perceive the initial position of a fast moving stimulus displaced in the direction of motion. On the basis of Kirschfeld and Kammers as well as Fröhlichs original assumption that metacontrast plays an important role in the emergence of the phenomenon, we predicted different amounts of misperception for stimulus enlargement compared to stimulus reduction. These basic predictions were confirmed in Experiment 1. In Experiment 2, we investigated whether an overestimation-bias might account for these results. But the overestimation of non-changing stimuli was too small to adequately explain the dissociation. In Experiment 3, we predicted and found different effects of the factor stimulus lightness on misperception in the enlargement and reduction condition. In Experiment 4, we showed that misperception in the enlargement condition is reduced when frames are used instead of filled stimuli, as in the earlier experiments. Results are discussed with respect to the original Fröhlich effect.

Long-term memory-based control of attention in multi-step tasks requires working memory: evidence from domain-specific interference

Evidence for long-term memory (LTM)-based control of attention has been found during the execution of highly practiced multi-step tasks. However, does LTM directly control for attention or are working memory (WM) processes involved? In the present study, this question was investigated with a dual-task paradigm. Participants executed either a highly practiced visuospatial sensorimotor task (speed stacking) or a verbal task (high-speed poem reciting), while maintaining visuospatial or verbal information in WM. Results revealed unidirectional and domain-specific interference. Neither speed stacking nor high-speed poem reciting was influenced by WM retention. Stacking disrupted the retention of visuospatial locations, but did not modify memory performance of verbal material (letters). Reciting reduced the retention of verbal material substantially whereas it affected the memory performance of visuospatial locations to a smaller degree. We suggest that the selection of task-relevant information from LTM for the execution of overlearned multi-step tasks recruits domain-specific WM.

Attentional capture by motion onsets is spatially imprecise

Using straight translatory motion of a visual peripheral cue in the frontoparallel plane, and probing target discrimination at different positions along the cues motion trajectory, we found that target orientation discrimination was slower for targets presented at or near the position of motion onset (4.2° off centre), relative to the onset of a static cue (Experiment 1), and relative to targets presented further along the motion trajectory (Experiments 1 and 2). Target discrimination was equally fast and accurate in the moving cue conditions relative to static cue conditions at positions further along the cues motion trajectory (Experiment 1). Moreover, target orientation discrimination was not slowed at the same position, once this position was no longer the motion onset position (Experiment 3), and performance in a target colour-discrimination task was not slowed even at motion onset (Experiment 4). Finally, we found that the onset location of the motion cue was perceived as being shifted in the direction of the cues motion (Experiment 5). These results indicate that attention cannot be as quickly or precisely shifted to the onset of a motion stimulus as to other positions on a stimulus’ motion trajectory.