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Recognition performance for a target letter embedded in a string of characters is worse than that for targets presented in isolation. This lateral masking (LM) effect is known to depend on target eccentricity and spacing between target and flankers (Bouma, 1970),indicating that LM arises in early visual processing due to interactions among visual features. The feature interaction account would predict that flankers consisting of similar features produce similar LM effects and that differences in LM produced by different types of flanker diminish with increasing target eccentricity and decreasing spacing. However, in a series of six experiments, this prediction was shown not to be true. Flankers that did not access a higher level code (e.g., pseudoletters or rotated letters) produced more LM than standard letter flankers. Moreover,effects of different flanker types were most pronounced for medium target eccentricities and medium spacings for which recognition performance scores ranged between 400A> and 600A>.

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Processes underlying crowding in visual letter recognition were examined by investigating effects of training. Experiment 1 revealed that training reduces crowding mainly for trained strings. This was corroborated in Experiment 2, where no training effects were obvious after 3 days of training when strings changed from trial to trial. Experiment 3 specified that after a short amount of training, learning effects remained specific to trained strings and also to the trained retinal eccentricity and the interletter spacing used in training. Transfer to other than trained conditions was observed only after further training. Experiment 4 showed that transfer occurred earlier when words were used as stimuli. These results thus demonstrate that part of crowding results from the absence of higher level representations of the stimulus. Such representations can be acquired through learning visual properties of the stimulus.

It has been found that emotional pictures are estimated to last longer than neutral ones. However, emotional and neutral stimuli often differ in their physical characteristics, too. Since this might also affect time perception, we present a method disentangling a possible confounding regarding the processing of physically different stimulus material. In the evaluative condition paradigm, participants, at first, learnt the association of neutral images with a certain Landolt ring and of emotional images with another Landolt ring with a different gap position. The conditioned Landolt rings were subsequently used in a temporal bisection task. In two experiments, the results revealed a temporal overestimation of Landolt rings conditioned with emotional pictures compared to neutral pictures showing that the temporal overestimation of emotional stimuli cannot be attributed to perceptual differences between neutral and emotional stimuli. The method provides the potential for investigating emotional effects on various perceptual processes.

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Augmented Reality (AR) uses computer-generated virtual information to enhance the user's information access. While numerous previous studies have demonstrated the large potential of AR to improve industrial processes by enhancing product quality and reducing production times it is still unclear if and how long term usage of such AR technology produces stress and strain. This paper presents an approach to use the analysis of Heart Rate Variability to objectively measure current user strain during different work tasks. Results of a user study comparing strain during an AR supported and a non-AR supported work task in a laboratory setting are presented and discussed.