Engineering data compendium. Human perception and performance. User's guide

The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design and military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from the existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by systems designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is the first volume, the User's Guide, containing a description of the program and instructions for its use

Humans combine the optic flow with static depth cues for robust perception of heading

The retinal flow during normal locomotion contains components due to rotation and translation of the observer. The translatory part of the flow-pattern is informative of heading, because it radiates outward from the direction of heading. However, it is not directly accessible from the retinal flow. Nevertheless, humans can perceive their direction of heading from the compound retinal flow without need for extra-retinal signals that indicate the rotation. Two classes of models have been proposed to explain the visual decomposition of the retinal flow into its constituent parts. One type relies on local operations to remove the rotational part of the flow field. The other type explicitly determines the direction and magnitude of the rotation from the global retinal flow, for subsequent removal. According to the former model, nearby points are most reliable for estimating one's heading. In the latter type of model the quality of the heading estimate depends on the accuracy with which the ego-rotation is determined and is therefore most reliable when based on the most distant points. We report that subjects underestimate the eccentricity of heading, relative to the fixated point in the ground plane, when the visible range of the ground plane is reduced. Moreover we find that in perception of heading, humans can tolerate more noise than the optimal observer (in the least squares sense) would do if only using optic flow. The latter finding argues against both schemes because ultimately both classes of model are limited in their noise tolerance to that of the optimal observer, which uses all information available in the optic flow. Apparently humans use more information than is present in the optic flow. Both aspects of human performance are consistent with the use of static depth information in addition to the optic flow to select the most distant points. Processing of the flow of these selected points provides the most reliable estimate of the ego-rotation. Subsequent estimates of the heading direction, obtained from the translatory component of the flow, are robust with respect to noise. In such a scheme heading estimates are subject to systematic errors, similar to those reported, if the most distant points are not much further away than the fixation point, because the ego-rotation is underestimated

Reading from a Head-Fixed Display during Walking: Adverse Effects of Gaze Stabilization Mechanisms

International audienceReading performance during standing and walking was assessed for information presented on earth-fixed and head-fixed displays by determining the minimal duration during which a numerical time stimulus needed to be presented for 50% correct naming answers. Reading from the earth-fixed display was comparable during standing and walking, with optimal performance being attained for visual character sizes in the range of 0.2 degrees to 1 degrees. Reading from the head-fixed display was impaired for small (0.2-0.3 degrees) and large (5 degrees) visual character sizes, especially during walking. Analysis of head and eye movements demonstrated that retinal slip was larger during walking than during standing, but remained within the functional acuity range when reading from the earth-fixed display. The detrimental effects on performance of reading from the head-fixed display during walking could be attributed to loss of acuity resulting from large retinal slip. Because walking activated the angular vestibulo-ocular reflex, the resulting compensatory eye movements acted to stabilize gaze on the information presented on the earth-fixed display but destabilized gaze from the information presented on the head-fixed display. We conclude that the gaze stabilization mechanisms that normally allow visual performance to be maintained during physical activity adversely affect reading performance when the information is presented on a display attached to the head

Designing pictorial stimuli for perceptual image difference experiments

Imaging system development often involves impact assessment of design choices. For systems that generate images for human consumption, such as cameras and displays, the effect of design decisions are often evaluated using `real-world\u27 images. System changes can have complicated effects on pictorial images that do not, as yet, have specified instrumental measurement methods. Consequently, human observers are often used in image quality assessment. However, human observers can react differently to complex pictorial stimuli both between observers and for a single observer over the course of a lengthy experiment. In an experimental setting, pictorial scenes present a greater opportunity than do uniform patches for observers\u27 individual differences to significantly impact the process. This study was conducted to increase the understanding of the optimal design of pictorial stimuli for more effective and efficient perceptual experiments. The goals of this dissertation were to: 1. Understand the impact of image content on visual attention and the consistency of image comparison experimental results 2. Understand how visual attention changes with successive viewing of pictorial images 3. Apply this understanding to develop guidelines for pictorial target design for perceptual image comparison experiments To achieve these objectives, a series of experiments were conducted to evaluate the impact of pictorial scene complexity on fixation and experimental response consistency. For these experiments, scenes exhibiting a range of perceived complexity were required. To select appropriate scenes, the concept of what constitutes a complex image was first considered. Experiment I was conducted to evaluate the number of areas perceived to be important in a variety of scenes. Observers were asked to identify the important areas of pictorial scenes. The scenes were also electronically segmented. The results from Experiment I were used to select scenes that provided a range of complexity for stimuli in Experiment II. This test examined the impact of image complexity on observer viewing behavior. Along with evaluating eye movements, observers were asked to describe the test scenes using up to five keywords. The results of Experiments I & II indicate that perceptual methods, segmentation, and eye-tracking generally provided consistent results with regard to image complexity. The exceptions involved issues of scale such that scenes viewed from afar blended into one significant object while one object viewed up close lacked a point of focus. The results of Experiment II were used to generate a proposal for guidelines for designing pictorial stimuli for image comparison experiments. Using these guidelines, scenes were selected and tested in Experiment III. The fixation consistency results of this experiment were generally as expected. However, fixation consistency did not always equate to experimental response consistency. Along with scene complexity, the image modifications (global versus local) and the difficulty of making the image equivalency decisions played a role in the experimental response as well. The results of Experiment III were used to confirm and augment the proposed guidelines. The guidelines developed in this study will benefit those conducting perceptual experiments with pictorial stimuli. Specific examples include color reproduction, perceptual color standards, and image equivalency research. A better understanding of what makes images equivalent may be useful in developing automated approaches to measuring image quality. And the guidelines may be useful in the improvement of the quality of images themselves. Fredembach (2011) has proposed that perceived image quality can be improved by increasing the perceived saliency of the main subject matter. These guidelines, including the use of blur, will be helpful in achieving this aim