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Our everyday interactions with the world are subject to affordance: the interaction that exists naturally between an object and the action possibilities inherent within it. Object affordances result from complex visuomotor interactions and are reflected in many processes, including reaching and grasping behaviours, distance judgments, and object identification. With the present study we extended current research on the use of affordances in visual searches of arrays to investigate whether guidance by affordance occurs in searches of real-world scenes and is the result of knowledge of target function (Experiment 1), and whether it is integrated with the use of scene context in guidance of search (Experiment 2). To investigate the contribution of object function to guidance by affordance in real-world scenes we tracked participants’ eye movements while they performed visual searches. The target objects were invented objects with invented functions that were learned by the participants prior to beginning search. By providing participants with information about only the features and functions of targets (and not about location) we omitted any effects on search from previously learned associations between the objects and their locations in the scene. This allowed us to examine guidance by affordance independently of traditional contextual effects. In Experiment 1 we compared the searches of participants who learned the functions of the targets to those who learned only the targets’ features. Results showed facilitation of visual search by knowledge of target function as compared against searches in which target function was not known. Experiment 2 compared searches for objects placed in locations congruent and incongruent with their function to show that guidance by affordance is benefitted by knowledge of target function in congruent searches. We concluded that guidance by affordance results from an understanding of the function of an object and the integration of that understanding into an understanding of the context of the scene as a whole / Thesis (Master, Psychology) -- Queen's University, 2012-08-30 16:36:26.184

The complex visual search involved in baggage screening requires operators to determine quickly whether a bag contains threatening objects that are embedded in a high degree of visual clutter. Methods for calculating visual clutter have been developed, and research has demonstrated the negative impact of clutter on search performance. The current study examined whether leveraging visual clutter information on the display during search could improve baggage screening performance above and beyond the conventional screening process. Ninety undergraduates searched x-ray images of bags for weapon items in a low fidelity baggage screening simulation; two clutter-based preview conditions displayed a limited portion of the bag to the participant before the entire bag was displayed. Eye movement data confirmed that the preview process guided the participant's attention to the corresponding previewed region. However, analysis of the baggage screening performance data showed there were no significant benefits associated with either clutter-based preview conditions compared with a control condition in which the entire bag was displayed for the duration of the trial. Thus, the results suggest that using clutter-based preview to guide visual attention does not substantially improve weapon detection performance. Despite this null effect, the current study provides additional evidence regarding the impact of visual clutter on complex search performance by demonstrating significant reductions in weapon detection accuracy and search efficiency due to increasing levels of visual clutter. Further research should explore methods for improving complex visual search by considering the negative impacts of visual clutter and ensuring that both attention guidance and object recognition processes are facilitated during search.

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The role of memory in repeated search tasks is contentious. Wolfe et al. (2000) have argued that participants do not learn a repeated scene and continue to perform a time-consuming search process for hundreds of trials. In contrast, Chun and Jiang (1998, 1999) have shown that search efficiency is improved for repeated versus new scenes and this learning can occur for either spatial layout independent of identity or identity independent of spatial layout. The experiments presented here demonstrate that participants learn a great deal about repeated search displays including the location of a particular item (both identity and location), the relative probability with which an item occurs in a location, and direction from the fixation point to the target. I argue that memory is established for these components and the reactivation of these memories by a repeated search display produces competition. This competitive target verification process takes time and can result in positive search slopes, which have been taken as evidence for memory-free search - a flawed logical argument.

Master of Science / Department of Psychology / Lester C. Loschky / The effect of blur/clarity contrast on selective attention was investigated in terms of how unique blur and/or clarity guides attention. Visual blur has previously been suggested to be processed preattentively using a dual-task paradigm (Loschky et al., 2014). Experiments 1 and 2 used rotated L and T visual search tasks with blur/clarity contrast being manipulated such that it was non-predictive of the target’s location. Each experiment was preceded by a legibility control study such that blurred and clear letters had similar accuracy and reaction times. This allowed for the results to be interpreted as changes in attention rather than difficulty identifying the letters because they were blurry. Results suggest that when non-predictive of target location, unique blur plays a passive role in selective attention in which it is ignored, neither capturing nor repelling attention to its spatial location, whereas unique clarity captures attention. The findings provide insight to the role that blur/clarity contrast plays in guiding visual attention, which can be implemented in visual software to help guide selective attention to critical regions of interest displayed on a computer screen.

Three experiments have been completed to investigate whether and how a software technique called real-time image mosaicing applied to a restricted field of view (FOV) might influence target detection and path integration performance in simulated aerial search scenarios, representing local and global spatial awareness tasks respectively. The mosaiced FOV (mFOV) was compared to single FOV (sFOV) and one with double the single size (dFOV). In addition to advancing our understanding of visual information in mosaicing, the present study examines the advantages and limitations of a number of metrics used to evaluate performance in path integration tasks, with particular attention paid to measuring performance in identifying complex routes. The highlights of the results are summarized as follows, according to Experiments 1 through 3 respectively. 1. A novel response method for evaluating route identification performance was developed. The surmised benefits of the mFOV relative to sFOV and dFOV revealed no significant differences in performance for the relatively simple route shapes tested. Compared to the mFOV and dFOV conditions, target detection performance in the local task was found to be superior in the sFOV condition. 2. In order to appropriately quantify the observed differences in complex route selections made by the participants, a novel analysis method was developed using the Thurstonian Paired Comparisons Method. 3. To investigate the effect of display size and elevation angle (EA) in a complex route environment, a 2x3 experiment was conducted for the two spatial tasks, at a height selected from Experiment 2. Although no significant differences were found in the target detection task, contrasts in the Paired Comparisons Method results revealed that route identification performance were as hypothesised: mFOV > dFOV > sFOV for EA = 90°. Results were similar for EA = 45°, but with mFOV being no different than dFOV. As hypothesised, EA was found to have an effect on route selection performance, with a top down view performing better than an angled view for the mFOV and sFOV conditions.

Previous research has suggested that making certain items visually salient, or highlighting, can speed performance in a visual search task. But designers of interfaces cannot always easily anticipate a user's target, and highlighting items other than the target can be associated with performance decrements. three experiments were performed which demonstrated that people's performance in a visual search task is differentially sensitive to highlighting's predictiveness of target location. That sensitivity depends upon the proportion of instances in which highlighting actually predicts target location. A cognitive model constructed using the ACT-R architecture inferred that people evaluate and adjust their visual search behavior at a very small level of the task. / pages 71-83 and 88-95 are missing from hard copy of text

Three experiments have been completed to investigate whether and how a software technique called real-time image mosaicing applied to a restricted field of view (FOV) might influence target detection and path integration performance in simulated aerial search scenarios, representing local and global spatial awareness tasks respectively. The mosaiced FOV (mFOV) was compared to single FOV (sFOV) and one with double the single size (dFOV). In addition to advancing our understanding of visual information in mosaicing, the present study examines the advantages and limitations of a number of metrics used to evaluate performance in path integration tasks, with particular attention paid to measuring performance in identifying complex routes. The highlights of the results are summarized as follows, according to Experiments 1 through 3 respectively. 1. A novel response method for evaluating route identification performance was developed. The surmised benefits of the mFOV relative to sFOV and dFOV revealed no significant differences in performance for the relatively simple route shapes tested. Compared to the mFOV and dFOV conditions, target detection performance in the local task was found to be superior in the sFOV condition. 2. In order to appropriately quantify the observed differences in complex route selections made by the participants, a novel analysis method was developed using the Thurstonian Paired Comparisons Method. 3. To investigate the effect of display size and elevation angle (EA) in a complex route environment, a 2x3 experiment was conducted for the two spatial tasks, at a height selected from Experiment 2. Although no significant differences were found in the target detection task, contrasts in the Paired Comparisons Method results revealed that route identification performance were as hypothesised: mFOV > dFOV > sFOV for EA = 90°. Results were similar for EA = 45°, but with mFOV being no different than dFOV. As hypothesised, EA was found to have an effect on route selection performance, with a top down view performing better than an angled view for the mFOV and sFOV conditions.