Subjectively interpreted shape dimensions as privileged and orthogonal axes in mental shape space

The shape of an object is fundamental in object recognition but it is still an open issue to what extent shape differences are perceived analytically (i.e., by the dimensional structure of the shapes) or holistically (i.e., by the overall similarity of the shapes). The dimensional structure of a stimulus is available in a primary stage of processing for separable dimensions, although it can also be derived cognitively from a perceived stimulus consisting of integral dimensions. Contrary to most experimental paradigms, the present study asked participants explicitly to analyze shapes according to two dimensions. The dimensions of interest were aspect ratio and medial axis curvature, and a new procedure was used to measure the participants' interpretation of both dimensions (Part I, Experiment 1). The subjectively interpreted shape dimensions showed specific characteristics supporting the conclusion that they also constitute perceptual dimensions with objective behavioral characteristics (Part II): (1) the dimensions did not correlate in overall similarity measures (Experiment 2), (2) they were more separable in a speeded categorization task (Experiment 3), and (3) they were invariant across different complex 2-D shapes (Experiment 4). The implications of these findings for shape-based object processing are discussed

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Space Station Human Factors Research Review. Volume 4: Inhouse Advanced Development and Research

A variety of human factors studies related to space station design are presented. Subjects include proximity operations and window design, spatial perceptual issues regarding displays, image management, workload research, spatial cognition, virtual interface, fault diagnosis in orbital refueling, and error tolerance and procedure aids

When seeing is more than looking:Intentional gaze modulates object desirability

Objects in the environment have a perceived value that can be changed through social influence. A subtle way to influence object evaluation is through eye gaze: Objects looked at by others are perceived as more likable than objects that are not looked at. In 3 experiments, we directly tested the hypothesis that this liking effect depends on the processing of the intentional relation between other's eye gaze and the object being looked at. To this end, we used a novel paradigm in which participants observed a face looking left or right behind an opaque barrier. Under all tested conditions, we found a gaze cueing effect on attention: Looked-at objects were categorized faster than looked-away objects. In contrast, observed gaze only led to a boost in affective evaluation for the target object when observers had the impression that the face could see the object behind the barrier, but not when observers had the impression that the face could not see the object. These findings indicate that observers make a sophisticated use of social gaze cues in the affective evaluation of objects: Objects looked at by others are liked more than objects looked away but only when others can see the objects

Visuomotor Adaptation Without Vision?

In 1995, an aftereffect following treadmill running was described, in which people would inadvertently advance when attempting to run in place on solid ground with their eyes closed. Although originally induced from treadmill running, the running-in-place aftereffect is argued here to result from the absence of sensory information specifying advancement during running. In a series of experiments in which visual information was systematically manipulated, aftereffect strength (AE), measured as the proportional increase (post-test/pre-test) in forward drift while attempting to run in place with eyes closed, was found to be inversely related to the amount of geometrically correct optical flow provided during induction. In particular, experiment 1 (n=20) demonstrated that the same aftereffect was not limited to treadmill running, but could also be strongly generated by running behind a golf-cart when the eyes were closed (AE=1.93), but not when the eyes were open (AE=1.16). Conversely, experiment 2 (n=39) showed that simulating an expanding flow field, albeit crudely, during treadmill running was insufficient to eliminate the aftereffect. Reducing ambient auditory information by means of earplugs increased the total distances inadvertently advanced while attempting to run in one place by a factor of two, both before and after adaptation, but did not influence the ratio of change produced by adaptation. It is concluded that the running-in-place aftereffect may result from a recalibration of visuomotor control systems that takes place even in the absence of visual input

Where Am I? A Meta-Analysis of Experiments on the Effects of Progress Indicators for Web Surveys

The use of progress indicators seems to be standard in many online surveys. Researchers include them in surveys in the hope they will help reduce drop-off rates. However, there is no consensus in the literature regarding their effects. In this meta-analysis, we analyzed 32 randomized experiments comparing drop-off rates of an experimental group who completed an online survey in which a progress indicator was shown to drop-off rates of a control group to whom the progress indicator was not shown. In all the studies, a drop-off was defined as a discontinuance of the survey (at any point) after it has begun, resulting in failure to complete the survey. Three types of progress indicators were analyzed: constant, fast-to-slow, and slow-to-fast. Our results show that, overall, using a constant progress indicator does not significantly help reduce drop-offs and that effectiveness of the progress indicator varies depending on the speed of indicator: Fast-to-slow indicators reduced drop-offs, whereas slow-to-fast indicators increased drop-offs. We also found that among the studies in which a small incentive was promised, showing a constant progress indicator increased the drop-off rate. These findings question the common belief that progress indicators help reduce drop-off rates

Visualizing Magnitude and Direction in Flow Fields

In weather visualizations, it is common to see vector data represented by glyphs placed on grids. The glyphs either do not encode magnitude in readable steps, or have designs that interfere with the data. The grids form strong but irrelevant patterns. Directional, quantitative glyphs bent along streamlines are more effective for visualizing flow patterns. With the goal of improving the perception of flow patterns in weather forecasts, we designed and evaluated two variations on a glyph commonly used to encode wind speed and direction in weather visualizations. We tested the ability of subjects to determine wind direction and speed: the results show the new designs are superior to the traditional. In a second study we designed and evaluated new methods for representing modeled wave data using similar streamline-based designs. We asked subjects to rate the marine weather visualizations: the results revealed a preference for some of the new designs

Seeing the invisible: The scope and limits of unconscious processing in binocular rivalry

When an image is presented to one eye and a very different image is presented to the corresponding location of the other eye, they compete for conscious representation, such that only one image is visible at a time while the other is suppressed. Called binocular rivalry, this phenomenon and its deviants have been extensively exploited to study the mechanism and neural correlates of consciousness. In this paper, we propose a framework, the unconscious binding hypothesis, to distinguish unconscious processing from conscious processing. According to this framework, the unconscious mind not only encodes individual features but also temporally binds distributed features to give rise to cortical representation, but unlike conscious binding, such unconscious binding is fragile. Under this framework, we review evidence from psychophysical and neuroimaging studies, which suggests that: (1) for invisible low level features, prolonged exposure to visual pattern and simple translational motion can alter the appearance of subsequent visible features (i.e. adaptation); for invisible high level features, although complex spiral motion cannot produce adaptation, nor can objects/words enhance subsequent processing of related stimuli (i.e. priming), images of tools can nevertheless activate the dorsal pathway; and (2) although invisible central cues cannot orient attention, invisible erotic pictures in the periphery can nevertheless guide attention, likely through emotional arousal; reciprocally, the processing of invisible information can be modulated by attention at perceptual and neural levels