Psychology Commons^™

Target Selection And Enhancement During Attentional Tracking, Marvin R. Maechler

Dartmouth College Ph.D Dissertations

At any waking moment, we are bombarded with more sensory information than we can fully process. Attention is necessary to deal with the dynamic world we live in. One fundamental function of vision and attention is to keep track of moving objects, but what are the targets of attention during tracking?

One of the first theories of attentional tracking predicted that targets would be selected at early processing stages. By employing the double-drift illusion, which dissociates physical and perceived positions of moving objects, we investigated which of these positions is selected for tracking. Contrary to earlier theories and in line …

Object Rigidity: Competition And Cooperation Between Motion-Energy And Feature- Tracking Mechanisms And Shape-Based Priors, Akihito Maruya, Qasim Zaidi Dr.

MODVIS Workshop

No abstract provided.

Resetting Of Auditory And Visual Segregation Occurs After Transient Stimuli Of The Same Modality, Nathan C. Higgins, Ambar G. Monjaras, Breanne D. Yerkes, David F. Little, Jessica E. Nave-Blodgett, Mounya Elhilali, Joel S. Snyder

Psychology Faculty Research

In the presence of a continually changing sensory environment, maintaining stable but flexible awareness is paramount, and requires continual organization of information. Determining which stimulus features belong together, and which are separate is therefore one of the primary tasks of the sensory systems. Unknown is whether there is a global or sensory-specific mechanism that regulates the final perceptual outcome of this streaming process. To test the extent of modality independence in perceptual control, an auditory streaming experiment, and a visual moving-plaid experiment were performed. Both were designed to evoke alternating perception of an integrated or segregated percept. In both experiments, …

Changes In Cortical Processing Following Unilateral Visual Cortex Deafferentation, Matthew Gannon

Graduate Theses and Dissertations

After the loss of inputs, cells in visual cortex adapt and begin representing space beyond their classical receptive fields. This ability for functional reorganization is a phenomenon known as neuroplasticity. Homonymous hemianopia is a unique case of this scenario that results from hemispheric deafferentation, or when all visual inputs in to one hemisphere of the brain are lost. This condition occurs due to unilateral damage of the post-chiasmatic geniculo-striate pathway, the network that carries visual information from one side of visual space to the visual cortex for processing. Damage to this pathway causes perceptual blindness in the side of space …

Visual Entrainment Of Perception-Related Neural Oscillations As A Mechanism For Maintaining Rhythmic Temporal Expectations Across A Wide Range Of Frequencies, Michael James Gray

Dissertations, Theses, and Capstone Projects

Visual sensitivity fluctuates rhythmically, in-synch with ongoing, EEG-recorded neural oscillations across a wide range of frequencies (~1-25hz). Some recent work has suggested that these perception-related neural oscillations can be entrained by rhythmic visual stimulation. Evidence is also emerging that the entrainment of ongoing oscillations in visual and auditory cortices is involved in rhythmic temporal expectations. In the introduction chapter, I attempt to bridge these bodies of literature and hypothesize that rhythmic visual stimuli automatically entrain ongoing, perception-related neural oscillations and that this mechanism supports the maintenance of rhythmic temporal expectations. Chapters 2 and 3 address this hypothesis from different angles. …

The Effects Of Emotionally Salient Unimodal And Multimodal Stimuli On Low-Level Visual Perception, Stephen Raymond Pierzchajlo

Electronic Thesis and Dissertation Repository

Sensory information can both impair and enhance low-level visual feature processing, and this can be significantly modulated depending on the whether this information matches the visual sensory modality. Emotionally significant visual and auditory stimuli can have opposing effects on attention. While task-irrelevant emotionally salient visual stimuli can often impair task attention, task-irrelevant emotionally salient auditory stimuli have been shown to enhance aspects of attention. To date, no study has directly compared how emotionally salient information presented to different sensory modalities can affect low-level vision. Using Gabor patches of differing contrasts to measure the threshold of visual perception, we hypothesized that …

Unimanual And Bimanual Haptic Shape Discrimination, Catherine Jane Dowell

Masters Theses & Specialist Projects

In the current study 24 younger adults and 24 older adults haptically discriminated natural 3-D shapes (bell peppers, Capsicum annuum) using unimanual (one hand used to explore two objects) and bimanual (both hands used, but each hand explored separate objects) successive exploration. Haptic exploration using just one hand requires somatosensory processing in only one cerebral hemisphere (the hemisphere contralateral to the hand being used), while bimanual haptic exploration requires somatosensory processing in both hemispheres. Previous studies related to curvature/shape perception have found either an advantage for unimanual exploration over bimanual exploration or no difference between the two conditions. In contrast …

A Mixture Model Demonstrates Use Of Distinct Strategies In A Global Motion Direction Task, Lanya Tianhao Cai, Benjamin T. Backus

MODVIS Workshop

Mixture models are well known in cognitive psychology, less so in vision. Are there cases where the data allow clear testing as to whether different strategies are employed in a task? Most psychophysical measurements manipulate a single staircase variable to map out a monotonic increasing function, but if performance is limited by different mechanisms over the range of the variable, classical fitting could be inappropriate. We present a data set and analyses that confirm the presence of two visual strategies addressing the same task, with the choice of strategies depending on the staircase variable. In a net-motion discrimination task, stimuli …

The Impact Of Affect On Neural Mechanisms Underlying Orientation Perception, Michelle L. Fowler

Dissertations, Theses, and Capstone Projects

The underlying mechanisms used to process 2D visual information to form a unified 3D percept of the world remain largely unknown. Previous work in our lab has shown that accurate 3D perception of textured surfaces depends on the presence of specific patterns of orientation flows in the retinal image. Recent research has shown that affective state may influence the visual perception of oriented patterns. Relative to neutral face stimuli, fearful face stimuli have been shown to increase sensitivity to orientation of low spatial frequency patterns and decrease sensitivity to orientation of high spatial frequency patterns. How affective state influences the …

Effects Of Motion Pattern Characteristics On The Perception Of Visual Acceleration, Alexandra S. Mueller

Electronic Thesis and Dissertation Repository

The ability to perceive visual motion is one that we use every day to perform goal-directed activities, such as intercepting or avoiding objects. As objects and observers rarely move at constant velocities, it is important to be able to detect changes in velocity. However, little attention has been paid to how we perceive visual acceleration in the literature. This thesis explored the influence of real world-relevant motion pattern characteristics on visual acceleration perception. Observers rarely see object motion with an unlimited field of view, and therefore we first examined how physically constraining the horizontal distance over which a stimulus can …

Short-Term Visual Deprivation, Tactile Acuity, And Haptic Solid Shape Discrimination, Charles E. Crabtree

Masters Theses & Specialist Projects

The visual cortex of human observers changes its functionality in response to visual deprivation (Boroojerdi et al., 2000). Behavioral studies have recently documented enhanced tactile abilities following a short period of visual deprivation (Facchini & Aglioti, 2003; Weisser, Stilla, Peltier, Hu, & Sathian, 2005). The current study investigated the effects of visual deprivation on two unique tactile tasks. While Facchini and Aglioti observed significant effects of visual deprivation, neither Wong, Hackeman, Hurd, and Goldreich (2011) nor Merabet et al. (2008) observed these effects. Corroborating these more recent results, no difference in grating orientation discrimination performance was observed between the sighted …

Contour Completion Through Depth Interferes With Stereoacuity, Dawn Vreven, Suzanne Mcvee, Preeti Verghese

Dawn L Vreven

Local disparity signals must interact in visual cortex to represent boundaries and surfaces of three-dimensional (3D) objects. We investigated how disparity signals interact in 3D contours and in 3D surfaces generated from the contours. We compared flat (single disparity) stimuli with curved (multi-disparity) stimuli. We found no consistent differences in sensitivity to contours vs. surfaces; for equivalent amounts of disparity, however, observers were more sensitive to flat stimuli than curved stimuli. Poor depth sensitivity for curved stimuli cannot be explained by the larger range of disparities present in the curved surface, nor by disparity averaging, nor by poor sensitivity to …

3d Shape Discrimination Using Relative Disparity Derivatives, Dawn Vreven

Dawn L Vreven

Three-dimensional (3D) shape discrimination could be achieved using relative disparity signals or it could be achieved using a higher-order disparity derivative detector. Two 3D shape discrimination tasks were used to distinguish between these possibilities: a within-shape task and a between-shape task. Disparity thresholds were larger when discriminating within the same shape than when discriminating between shapes. More importantly, within-shape discriminations were dependent on the pedestal disparity (distance from fixation) whereas between-shape discriminations were not. The results suggest that a mechanism sensitive to higher-order disparity derivatives can achieve discrimination between different 3D shapes.

Is Pigmentation Important For Face Recognition? Evidence From Contrast Negation, Richard Russell, Pawan Sinha, Irving Biederman, Marissa Nederhouser

Psychology Faculty Publications

It is extraordinarily difficult to recognize a face in an image with negated contrast, as in a photographic negative. The variation among faces can be partitioned into two general sources: (a) shape and (b) surface reflectance, here termed 'pigmentation'. To determine whether negation differentially affects the processing of shape or pigmentation, we made two sets of faces where the individual faces differed only in shape in one set and only in pigmentation in the other. Surprisingly, matching performance was significantly impaired by contrast negation only when the faces varied in pigmentation. This provides evidence that the perception of pigmentation, not …

Temporal Discrimination And A Free-Operant Psychophysical Procedure, D. Alan Stubbs

Psychology Faculty Scholarship

Pigeons were presented a series of keylight time periods (separated by blackouts) during which two response keys were lit, one by blue light and the other either by orange or green. Blue-key responses changed the color on the other key. Orange-key responses sometimes produced food during the first half of a time period; green-key responses sometimes produced food during the second half. In three experiments, the probability of a green-key response increased as a function of elapsed time. Experiment 1 compared performance when the duration of the keylight periods was varied across a wide range. Discrimination performance was similar across …