Object experts quickly and accurately discriminate objects within their domain of expertise. Although expert recognition has been extensively studied both at the behavioral- and neural-levels in both real-world and laboratory trained experts, we know little about the visual features and perceptual strategies that the expert learns to use in order to make fast and accurate recognition judgments. Thus, the aim of this work was to identify the visual features (e.g., color, form, motion) and perceptual strategies (e.g., fixation pattern) that real-world experts employ to recognize objects from their domain of expertise. Experiments 1 to 3 used psychophysical methods to test the role of color, form (spatial frequencies), and motion, respectively, in expert object recognition. Experiment 1 showed that although both experts and novices relied on color to recognize birds at the family level, analysis of the response time distribution revealed that color facilitated expert performance in the fastest and slowest trials whereas color only helped the novices in the slower trials. Experiment 2 showed that both experts and novices were more accurate when bird images contained the internal information represented by a middle range of SFs, described by a quadratic function. However, the experts, but not the novices, showed a similar quadratic relationship between response times and SF range. Experiment 3 showed that, contrary to our prediction, both groups were equally sensitivity to global bird motion. Experiment 4, which tested the perceptual stategies of expert recognition in a gaze-contingent eye-tracking paradigm, showed that only in the fastest trials did experts use a wider range of vision. Experiment 5, which examined the neural representations of categories within the expert domain, suggested that the mechanisms that represents within-categories of faces also represented within-categories from the domain of expertise, but not the novice domain. Collectively, these studies suggest that expertise influence visual discrimination mechanisms such that they become more sensitive to the visual dimensions upon which the expert domains are discriminated. / Graduate / 2018-12-12

No description available.

Previous studies have indicated that concurrent multimodal stimulation can interfere with prenatal perceptual learning. However, the nature and extent of this interference is not well understood. This study further assessed this issue by exposing three groups of bobwhite quail embryos to (a) no unusual prenatal stimulation, (b) a bobwhite maternal call, or (c) a maternal call + light compound in the period prior to hatching. Experiments differed in terms of the types of stimuli presented during postnatal preference tests (Exp 1 = familiar call vs. unfamiliar call; Exp 2 = familiar compound vs. unfamiliar compound; Exp 3 = familiar compound verses unfamiliar call; Exp 4 = familiar call vs. unfamiliar compound). Embryos receiving no supplemental stimulation showed no preference between stimulus events in all testing conditions. Embryos receiving exposure to a unimodal call preferred the familiar call over the unfamiliar call regardless of the presence or absence of patterned light during testing. Embryos receiving concurrent audio-visual exposure showed no preference between stimulus events in Exp 1 and Exp 4, but did prefer the familiar call when it was paired with light during testing (Exp 2 and 3). These findings suggest that concurrent multimodal stimulation does not interfere with prenatal perceptual learning by overwhelming the young organism's limited attentional capacities. Rather, multimodal biases what information is attended to during exposure and subsequent testing. Results are discussed within an attentional-bias framework, which maintains that young organisms tend to initially process non-redundant compound events as integrative units rather than processing the components of the compound separately. / Master of Science

Discrimination between similar stimuli is enhanced more by intermixed pre-exposure than by blocked pre-exposure to those stimuli. The salience modulation account of this intermixed-blocked effect proposes that the unique elements of intermixed stimuli are more salient than those of blocked stimuli. The inhibition account proposes that inhibitory links between the unique elements of intermixed stimuli enhance discrimination. The current thesis evaluated the two accounts in their ability to explain this effect in humans. In Experiments 1 and 2, categorisation and same-different judgements were more accurate for intermixed than for blocked stimuli. This indicates that intermixed pre-exposure decreases generalisation and increases discriminability more than does blocked pre-exposure. In Experiments 3 ?? 5, same-different judgements were more accurate when at least one of the two stimuli was intermixed. This enhanced discrimination was not confined to two stimuli that had been directly intermixed. These results are better explained by salience modulation than by inhibition. Experiments 6 ?? 8 employed dot probe tasks, in which a grid stimulus was followed immediately by a probe. Neither intermixed nor blocked stimuli showed facilitated reaction times when the probe appeared in the location of the unique element. In Experiments 9 ?? 11 participants learned to categorise the intermixed unique elements more successfully than the blocked unique elements, but only when the unique elements were presented on a novel background during categorisation. Experiments 6 ?? 11 provide weak evidence that the intermixed unique elements are more salient than their blocked counterparts. In Experiment 12, participants were presented with the shape and location of a given unique element, and were required to select the correct colour. Performance was more accurate for intermixed than for blocked unique elements. In Experiment 13, participants learned to categorise intermixed, blocked and novel unique elements. Performance was better for intermixed than for blocked and novel unique elements, which did not differ. None of the proposed mechanisms for salience modulation anticipate these results. The intermixed-blocked effect in human perceptual learning is better explained by salience modulation than by inhibition. However, the salience modulation accounts that have been proposed received little support. An alternative account of salience modulation is considered.

Thesis (M.S.)--Ball State University, 2009. / Title from PDF t.p. (viewed on Dec. 14, 2009). Includes bibliographical references (p. 38-39).

published_or_final_version / Speech and Hearing Sciences / Doctoral / Doctor of Philosophy

No description available.

No description available.

No description available.

Discrimination between similar stimuli is enhanced more by intermixed pre-exposure than by blocked pre-exposure to those stimuli. The salience modulation account of this intermixed-blocked effect proposes that the unique elements of intermixed stimuli are more salient than those of blocked stimuli. The inhibition account proposes that inhibitory links between the unique elements of intermixed stimuli enhance discrimination. The current thesis evaluated the two accounts in their ability to explain this effect in humans. In Experiments 1 and 2, categorisation and same-different judgements were more accurate for intermixed than for blocked stimuli. This indicates that intermixed pre-exposure decreases generalisation and increases discriminability more than does blocked pre-exposure. In Experiments 3 ?? 5, same-different judgements were more accurate when at least one of the two stimuli was intermixed. This enhanced discrimination was not confined to two stimuli that had been directly intermixed. These results are better explained by salience modulation than by inhibition. Experiments 6 ?? 8 employed dot probe tasks, in which a grid stimulus was followed immediately by a probe. Neither intermixed nor blocked stimuli showed facilitated reaction times when the probe appeared in the location of the unique element. In Experiments 9 ?? 11 participants learned to categorise the intermixed unique elements more successfully than the blocked unique elements, but only when the unique elements were presented on a novel background during categorisation. Experiments 6 ?? 11 provide weak evidence that the intermixed unique elements are more salient than their blocked counterparts. In Experiment 12, participants were presented with the shape and location of a given unique element, and were required to select the correct colour. Performance was more accurate for intermixed than for blocked unique elements. In Experiment 13, participants learned to categorise intermixed, blocked and novel unique elements. Performance was better for intermixed than for blocked and novel unique elements, which did not differ. None of the proposed mechanisms for salience modulation anticipate these results. The intermixed-blocked effect in human perceptual learning is better explained by salience modulation than by inhibition. However, the salience modulation accounts that have been proposed received little support. An alternative account of salience modulation is considered.