acase@tulane.edu / The following dissertation project included three behavioral experiments indexing spatial attention in the auditory modality. Each experiment varied in terms of predictable stimulus features on the task, and demonstrated differential engagement of spatial attention depending on if stimulus location or identity was predictable on any given trial. Experiment 1 involved no predictable features. Experiment 2 involved predictable sound identity presented from unpredictable locations. Experiment 3 presented sounds with unpredictable identity from a predictable location. All experiments involved judging the identity of the sound in a two-choice reaction time style task. All three experiments also included memory load, loading memory with sound identities or locations on a given block. A dual-task design was employed in order to investigate Reaction Time and Accuracy effects related to maintaining features in memory that were also present during the selective attention task. Experiments employed conditions with variable levels of overlap across features in memory and attention; investigating overlap at the level of feature-type (i.e. maintaining one color in memory while attending to another) and at the level of specific feature (i.e. attending to the color blue while it also happens to be retained in memory). Results demonstrated improved reaction time and accuracy for expected sounds and sounds from expected locations. Additionally, memory load showed interference on the basis of load-type (reflective of specialized load effects), and showed slower reaction times for stimuli that contained features which overlapped with features in memory (primarily for unexpected stimuli). These results contradicted findings in the visual modality that have reported faster reaction times for stimuli that match with features stored in memory. This difference in findings is most likely driven by differences between auditory and visual attention, the impact of unpredictability on overlap, or both. / 1 / Maxwell Anderson

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A key problem in model-based object recognition is selection, namely, the problem of isolating regions in an image that are likely to come from a single object. This isolation can be either based solely on image data (data-driven) or can incorporate the knowledge of the model object (model-driven). In this paper we present an approach that exploits the property of closely-spaced parallelism between lines on objects to achieve data and model-driven selection. Specifically, we present a method of identifying groups of closely-spaced parallel lines in images that generates a linear number of small-sized and reliable groups thus meeting several of the desirable requirements of a grouping scheme for recognition. The line groups generated form the basis for data and model-driven selection. Data-driven selection is achieved by selecting salient line groups as judged by a saliency measure that emphasizes the likelihood of the groups coming from single objects. The approach to model-driven selection, on the other hand, uses the description of closely-spaced parallel line groups on the model object to selectively generate line groups in the image that are likely to eb the projections of the model groups under a set of allowable transformations and taking into account the effect of occlusions, illumination changes, and imaging errors. We then discuss the utility of line groups-based selection in the context of reducing the search involved in recognition, both as an independent selection mechanism, and when used in combination with other cues such as color. Finally, we present results that indicate a vast improvement in the performance of a recognition system that is integrated with parallel line groups-based selection.

The present study investigated the claim that positive mood broadens the scope of attention to include irrelevant information, and if so, whether this loosening of attentional control has longer term cognitive consequences. In Experiment 1, participants in an induced happy mood were more influenced by distracting information that interfered with responses in the global-local task, particularly when this information was global in nature. Experiment 2 demonstrated that, when previously irrelevant information became solutions on a subsequent task, implicit memory for this distraction was positively correlated with naturally-occurring positive mood. This study corroborates findings that individuals in a happy mood are more affected by distracting irrelevant information. Furthermore, this widened scope of attention can facilitate performance on a subsequent task, a finding with implications for the relationship between positive mood and creativity.

Detecting acoustic changes in our environment, such as a rattlesnake’s sudden approach, can be essential for survival. Although auditory change detection has been intensively investigated using sequentially-presented sounds, very little is known about how we detect changes in a natural, complex scene comprised of multiple concurrent sounds. The present study used a location-switch change deafness paradigm; on each trial, participants listened to two consecutive auditory scenes, consisting of three natural sounds played in distinct locations, and reported if the two scenes were the same or identified the two sounds that switched locations. Directing a listener’s attention to a changing sound improved accuracy and decreased reaction time, relative to uncued trials. However, when participants’ attention was invalidly directed to a non-changing sound object, performance suffered. Further analyses showed that these effects could not be explained by energetic masking. Thus, attention is necessary for change identification in complex auditory scenes.

To examine whether executive attention is affected by perceptual attention, we manipulated executive load in a single experiment. Moreover, we assessed the influence of normal aging on knowledge-driven and attentional sensory-driven processes. Healthy young and older adult participants viewed visual streams of superimposed face/place images at low and high perceptual loads while making sex judgments on each face component and then completing a low or high executive load working memory task. Younger adults exhibited independent behavioural patterns for the executive and perceptual load manipulations due to intact selective attention mechanisms, whereas older adults exhibited interacting processes. This is evidenced by the performance of older adults on concurrent executive and perceptual tasks, which was associated with working memory capacity; whereas younger adults did not exhibit this dependency. Selective attention processes that are independent in younger populations seem to converge in older populations due to decrements in executive and perceptual attention domains.

Detecting acoustic changes in our environment, such as a rattlesnake’s sudden approach, can be essential for survival. Although auditory change detection has been intensively investigated using sequentially-presented sounds, very little is known about how we detect changes in a natural, complex scene comprised of multiple concurrent sounds. The present study used a location-switch change deafness paradigm; on each trial, participants listened to two consecutive auditory scenes, consisting of three natural sounds played in distinct locations, and reported if the two scenes were the same or identified the two sounds that switched locations. Directing a listener’s attention to a changing sound improved accuracy and decreased reaction time, relative to uncued trials. However, when participants’ attention was invalidly directed to a non-changing sound object, performance suffered. Further analyses showed that these effects could not be explained by energetic masking. Thus, attention is necessary for change identification in complex auditory scenes.

To examine whether executive attention is affected by perceptual attention, we manipulated executive load in a single experiment. Moreover, we assessed the influence of normal aging on knowledge-driven and attentional sensory-driven processes. Healthy young and older adult participants viewed visual streams of superimposed face/place images at low and high perceptual loads while making sex judgments on each face component and then completing a low or high executive load working memory task. Younger adults exhibited independent behavioural patterns for the executive and perceptual load manipulations due to intact selective attention mechanisms, whereas older adults exhibited interacting processes. This is evidenced by the performance of older adults on concurrent executive and perceptual tasks, which was associated with working memory capacity; whereas younger adults did not exhibit this dependency. Selective attention processes that are independent in younger populations seem to converge in older populations due to decrements in executive and perceptual attention domains.

The present study investigated the claim that positive mood broadens the scope of attention to include irrelevant information, and if so, whether this loosening of attentional control has longer term cognitive consequences. In Experiment 1, participants in an induced happy mood were more influenced by distracting information that interfered with responses in the global-local task, particularly when this information was global in nature. Experiment 2 demonstrated that, when previously irrelevant information became solutions on a subsequent task, implicit memory for this distraction was positively correlated with naturally-occurring positive mood. This study corroborates findings that individuals in a happy mood are more affected by distracting irrelevant information. Furthermore, this widened scope of attention can facilitate performance on a subsequent task, a finding with implications for the relationship between positive mood and creativity.