Cognitive judgments about an object's location are distorted by the presence of a large frame offset left or right of an observer's midline. Sensorimotor responses, however, seem immune to this induced Roelofs illusion, with observers able to accurately point to the target's location. These findings have traditionally been used as evidence for a dissociation of the visual processing required for cognitive judgments and sensorimotor responses. However, a recent alternative hypothesis suggests that the behavioral dissociation is expected if the visual system uses a single frame of reference whose origin (the apparent midline) is biased toward the offset frame. The two theories make qualitatively distinct predictions in a paradigm in which observers are asked to indicate the direction symmetrically opposite the target's position. The collaborative findings of two laboratories clearly support the biased-midline hypothesis.
Studies of change blindness suggest that we bring only a few attended features of a scene, plus a gist, from one visual fixation to the next. We examine the role of gist by substituting an original image with a second image in which a substitution of one object changes the gist, compared with a third image in which a substitution of that object does not change the gist. Small perceptual changes that affect gist were more rapidly detected than perceptual changes that do not affect gist. When the images were scrambled to remove meaning, this difference disappeared for seven of the nine sets, indicating that gist and not image features dominated the result. In a final experiment a natural image was masked with an 8x8 checker pattern, and progressively substituted by squares of a new natural image of the same gist. Spatial jitter prevented fixation on the same square for the sequence of 12 changes. Observers detected a change in an average of 2.1 out of 7 sequences, indicating strong change blindness for images of the same gist but completely different local features. We conclude that gist is automatically encoded, separately from specific features.
Understanding mobile users and their behaviors in context, across multiple countries and cultures, is challenging and costly. However, the reward of creating a mobile application that meets mobile users' needs (and is actually used -not deleted within days of being downloaded) is priceless to the user in terms of productivity, the employer by keeping data updated, and the developer by producing a successful application.To develop such applications, mobile HCI professionals need to identify mobile users' daily mobile habits and tasks completed with their devices. To uncover unexpected uses and a range of contexts, we recommend using a photo diary technique in conjunction with other ethnographic methods. Conducting mobile photo diaries will help mobile HCI professionals in their application decision making process, by giving them additional insights into their users that may have been inaccessible or unthought-of before, and visually rich deliverables to share with management.
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