Cognitive control of eye movements in reading and visual search: Evidence from frequency-based effects

Experiments in this dissertation investigate the role of cognition in eye-movement behavior during scanning and reading. Shorter and fewer fixations on the more frequent and predictable words have been observed during reading, but not when scanning text for a target word, e.g., zebra (e.g., Rayner & Raney, 1996). Past research has employed these effects of word frequency and predictability to argue that cognition drives eye movements during reading, but not during scanning. Similarly, the present studies use effects of stimulus frequency and predictability to index cognitive control of eye-movement behavior. Experiments 1 and 2 focus on the frequency effects for non-word and word stimuli, respectively. Experiment 1 employed clusters of Landolt Cs to examine how the gap size of and frequency of exposure to clusters affected eye movements during a scanning task. The findings demonstrated that, in parallel to word frequency effects observed in reading, more frequent clusters elicited fewer and shorter fixations. Experiment 2 compared eye-movement behavior on fully-crossed high- and low-frequency adjective-noun pairs embedded in paragraphs when participants were reading vs. scanning for a target word with an asterisk (e.g., “h*rse”), a word containing the letter "q" (e.g., “quilt”), or a word rhyming with "blue" (e.g., “shoe”). The results demonstrated that eye-movement measures are affected by frequency in the tasks requiring in-depth processing, such as reading and rhyme-judgment, but not in shallow-processing tasks like asterisk-detection. Experiments 3 and 4 focus on the frequency-based predictability effects for non-word and word stimuli, respectively. Experiment 3 employed similar materials to Experiment 1 and, in addition, manipulated frequency for pairs of clusters. The more predictable clusters in the repeating pairs elicited fewer fixations, providing tentative evidence of transitional predictability effects during scanning. Experiment 4 examined the effect of transitional probability in reading by increasing the frequency of co-occurrence for pairs of words (e.g., tulip’s blossoms) in paragraphs of text. The more predictable words elicited shorter first fixation durations, suggesting that co-occurrence frequency may result in forming short-term predictions during reading. Cumulatively, the findings demonstrate that cognitive effects are not unique to reading, and afford a more sophisticated characterization of the cognitive-oculomotor coordination

dynamic

use of microworlds to stud

The Adaptive Character of the Attentional System: Statistical Sensitivity in a Target Localization Task

this article was supported by Grants 1R01 MH52808-01 and 2-R01MH52808 from the National Institute of Mental Health, Grant N0001495 -1-0223 from the Office of Naval Research, Grant SBR-9873465 from the National Science Foundation, and Grant F49620-97-1-0054 from the Air Force Office of Scientific Researc

The Use of Microworlds to Study Dynamic Decision Making

Dynamic decision-making (DDM) research grew out of a perceived need for understanding how people control dynamic, complex, real-world systems. DDM has describable characteristics and, with some unavoidable sacrifice of realism, is suitable for study in a laboratory setting through the use of complex computer simulations commonly called ‘microworlds’. This paper presents a taxonomic definition of DDM, an updated review of existing microworlds and their characteristics, and a set of cognitive demands imposed by DDM tasks. Although the study of DDM has garnered little attention to date, we believe that both technological advancement and the relationships between DDM and naturalistic decision making, complex problem solving, and general systems theory have made DDM a viable process by which to study how people make decisions in dynamic, real-world environments

The Relationships Between Cognitive Ability and Dynamic Decision Making

his study investigated the relationships between cognitive ability (as assessed by the Raven Progressive Matrices Test [RPM] and the Visual-Span Test [VSPAN]) and individuals’ performance in three dynamic decision making (DDM) tasks (i.e., regular Water Purification Plant [WPP], Team WPP, and Firechief). Participants interacted repeatedly with one of the three microworlds. Our results indicate a positive association between VSPAN and RPM scores and between each of those measures and performance in the three dynamic tasks. Practice had no effect on the correlation between RPM score and performance in any of the microworlds, but it led to an increased correlation between VSPAN score and performance in Team WPP. The pattern of associations between performance in microworlds and assessments of cognitive ability was consistent with the task requirements of the microworlds. These findings provide insight into the cognitive demands of dynamic decision making and the dynamics of the relationships between cognitive ability and performance with task practice. D 2004 Elsevier Inc. All rights reserved

The emergence of frequency effects in eye movements

A visual search experiment employed strings of Landolt Cs to examine how the gap size of and frequency of exposure to distractor strings affected eye movements. Increases in gap size were associated with shorter first-fixation durations, gaze durations, and total times, as well as fewer fixations. Importantly, both the number and duration of fixations decreased with repeated exposures. The findings provide evidence for the role of cognition in guiding eye-movements, and a potential explanation for word-frequency effects observed in reading

The adaptive character of the attentional system: statistical sensitivity in a target localization task.

A localization task required participants to indicate which of 4 locations contained a briefly displayed target. Most displays also contained a distractor that was not equally probable in these locations, affecting performance dramatically. Responses were faster when a display had no distractor and almost as fast when the distractor was in its frequent location. Conversely, responses were slower when targets appeared in frequent-distractor locations, even thou targets were equally likely in each location. Negative-priming effects were reliably smaller when targets followed distractors in the frequent-distractor location compared to the rare-distractor location, challenging the episodic-retrieval account Experiment 2 added a 5th location that rarely displayed distractors and never targets, yet responses slowed most when distractors appeared there. The results confirmed that the attentional system is sensitive to first- and higher-order statistical patterns and can make short- and long-term adjustments in preferences based on prior history of inspecting unsuccessful locations.</p

The Performance of Graphene-Enhanced THz Grating: Impact of the Gold Layer Imperfectness

We report the performance of a graphene-enhanced THz grating fabricated by depositing a gold layer on the femtosecond micromachined SiO2 substrate. The morphology of the gold plated patterned substrate was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM), while the quality of the chemical vapor deposition (CVD) graphene was evaluated by Raman spectroscopy. The electromagnetic (EM) response of the metasurface comprising the graphene sheet and the gold plated substrate was studied by THz time domain spectroscopy in the 100 GHz–1 THz frequency range. We employed the finite elements method (FEM) to model the metasurface EM response by adjusting the ac conductivity of the gold layer covering the patterned SiO2 substrate to reproduce the measured transmission/reflection spectra. The results of the numerical simulation reveal the impact of the imperfectness of the gold layer on the performance of the THz metasurface. The experimental results are well described in terms of the Drude–Smith model of metal conductivity that takes into account the anisotropic scattering of the carriers in thin metal films

Serial or parallel? Using depth-of-processing to examine attention allocation during reading

This paper presents an experiment investigating attention allocation in four tasks requiring varied degrees of lexical processing of 1-4 simultaneously displayed words. Response times and eye movements were only modestly affected by the number of words in an asterisk-detection task but increased markedly with the number of words in letter-detection, rhyme-judgment, and semantic-judgment tasks, suggesting that attention may not be serial for tasks that do not require significant lexical processing (e.g., detecting visual features), but is approximately serial for tasks that do (e.g., retrieving word meanings). The implications of these results for models of readers' eye movements are discussed