Browsing by Subject "Perception"

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APAL/Konya Higher Order Affordances in Soccer 2020-22
(2023-01-30) Peker, Alper Tunga; Boge, Veysel; Bailey, George S.; Wagman, Jeffrey, B; Stoffregen, Thomas A.; tas@umn.edu; Stoffregen, Thomas A.; Affordance Perception-Action Laboratory
This dataset contains all data collected for APAL's "Higher-Order Affordances in Soccer" JEP Publication, 2022. This data allowed for valued additions to be made to both the affordance literature, and the literature examining human performance in sport. We are releasing this data per APA standards upon the acceptance of our paper.
Context-dependent adaptation in the visual system
(2017-12) Mesik, Juraj
The visual system continuously adjusts its sensitivities to various visual features so as to optimize neural processing, a phenomenon known as adaptation. Although this rapid form of plasticity has been extensively studied across numerous sensory modalities, it remains unclear if its dynamics can change with experience. Specifically, the world we live in is composed of many different environments, or contexts, each of which contains its own statistical regularities. For example, forests contain more vertical energy and greenish hues than a desert landscape. Here we investigated the possibility that through experience, the visual system can learn statistical regularities in the visual input, and use this knowledge to adapt more quickly. In two sets of experiments, participants repeatedly adapted to previously unexperienced regularities in orientation statistics over the course of 3-4 sessions. They adapted either to rapidly presented sequences of oriented gratings containing orientation biases, or to natural visual input that was filtered to alter its orientation statistics. We found that experience did increase adaptation rate, but only in the experiments where participants adapted to a single set of altered statistics of natural input. We found no changes in adaptation rate in experiments where participants periodically switched between adapting to different statistical regularities. These results demonstrate that adaptation and experience can interact under some circumstances.
Effects of Avatar Hand-size Modifications on Size Judgments of Familiar and Abstract Objects in Virtual Reality
(2019-06) Patterson, Zachary
Many research studies have investigated spatial understanding within virtual envi- ronments, ranging from distance estimation, size judgments, and perception of scale. Eventually, this knowledge will help us to create virtual environments that better match our spatial abilities within natural environments. To further understand how people interpret the size of virtual objects, we present an experiment that utilizes a proprioceptive-based size estimation measure designed to elicit a three-dimensional judgment of an object’s size using a box-sizing task. Participants viewed both ab- stract and familiar objects presented within action-space in a virtual environment and were asked to make an axis-aligned box the same size as the object they previously observed. A between-subjects manipulation modified a participant’s avatar hand size to be either 80%, 100% or 120% of their measured hand size. Results indicate that the avatar hand size manipulation scales various factors of these size judgments in the three dimensions. Additionally, whether an object was abstract or a familiar size object produced distinctly different size judgments.
Effects of cognitive stress in handwriting movements in a pursuit loop-drawing task.
(2010-11) Yank, Jane Redfield
The effects of concurrently presented visual traces of hand movements on timing, smoothness, and spatial accuracy were investigated during a loop-drawing tracking task. Thirty-five healthy young right-handed adults used a stylus on a digitizing tablet to track a left-to-right loop-drawing animation presented on a computer monitor. A dot target moved over a template of twelve connected cursive letter e’s, leaving a track as it drew over each loop in the series. Participants were instructed to draw along with the target to reproduce the shape of the loops at the tempo of the target. Participants performed sixteen trials in a 2 × 2 design, eight trials with their trace visible on the computer monitor and eight trials without a visible trace, half with a constant target rate and half with a variable rate change mid-trial. Spatial accuracy was greater when the participant trace was visible, as expected (p < .0001). An inverse relationship was found between drawing speed and spatial accuracy, consistent with the expectation that more spatial errors would occur at increased speeds. However, timing accuracy (p < .0001) and smoothness (p = .0026) decreased when the participant trace was visible. These results suggest that the visual trace of the participant tracking presented on the computer screen disrupted timing characteristics of perception-action coupling and increased the complexity of the task. Findings are discussed in the context of cognitive load.
Elementary teachers' perceptions of environmental education.
(2010-12) Bengtson, Karen Jo Maier
Efforts to develop and implement environmental education (EE) in classrooms across the United States need to be grounded in understanding teachers' perceptions of EE. A case study format was selected as an effective means of eliciting a wide range of the teachers' perceptions and capturing an in-depth elaboration of the complexity and internal consistency of those perceptions. The research questions for this study are: 1) What are the participating elementary teachers' perceptions of EE? 2) What are the participating elementary teachers' perceptions of ideal EE? 3) What are the participating elementary teachers' perceptions of the reality of teaching EE? And 4) How do the individual participating teachers' three types of EE perceptions misalign? Case studies of four elementary classroom teachers from the same school building were constructed from survey questions, interviews, and resource materials. Analysis and interpretation of the data were conducted using two sets of descriptors, strength and development, of the identified themes. The major implications of this study include (a) efforts supporting the implementation of EE need to account for the context that exists in the school, and how the structure of the school interplays with the implementation; (b) the need for teacher professional development in EE with considerations for teaching context, teachers' personal EE connections, and variability in teacher understanding, and (c) the complexity and diversity in the expression of teachers' EE perceptions needs to be attended in EE implementation efforts, as well as in research exploring teacher perceptions of EE.
Geoai: Challenges and Opportunities
(2020-05) Xie, Yiqun
Spatial data have tremendous value and are necessary components in many important societal applications. In recent years, our world has been witnessing a revolution brought by spatial technologies (e.g., Google Maps, Waze, Uber, Lyft, Grubhub, Lime, autonomous driving). According to a McKinsey Global Institute report, location data will generate about $600 billion annual revenue by 2020 with applications in energy, health, retail, etc. The world's economy also heavily relies on location and time data from over 2 billion GPS receivers, and these data are essential to many applications such as banks, airlines, police, emergency services, and telecommunications. Meanwhile, new types of spatial data are emerging at unprecedented scales and varieties (e.g., 25GB/hour per connected vehicle, 47.7PB per year by NASA by 2022). While spatial data are critical, valuable and collected at massive scales, they pose great challenges to traditional artificial intelligence (AI) techniques when applied to important societal problems. This thesis addresses three of these challenges. First, spatial data (e.g., crime or disease distribution, air quality) are often directly linked to our lived environments. As a result, decisions made on such data tend to have direct impacts on the life of citizens, and thus require statistical robustness to avoid errors which can have high economic and social costs (e.g., false alarm of a crime hotspot). Second, spatial data exhibit interdependency and variability, violating the common i.i.d. (identically and independently distributed) assumption in traditional statistics. This introduces new challenges to traditional optimization problems where spatial interdependency between nearby locations is often neglected and understudied (e.g., spatial contiguity required in land allocation). Finally, data and domain knowledge gaps are common in geospatial problems. For example, while Earth observation imagery is available in the tens of petabytes, there is very limited training data for many important objects or events (e.g., tree data for preventing fires and power blackouts) and expert knowledge is often required to create such data. This thesis investigates novel GeoAI techniques to explicitly address these challenges posed by spatial data and problems in three types of AI tasks: learning (i.e., unsupervised clustering); planning (i.e., spatial constraints and optimization); and perception (i.e., geospatial object mapping). First, the thesis proposes a significant DBSCAN approach for statistically-robust clustering to control the rate of spurious patterns. This work introduces a modeling of statistical significance for DBSCAN as well as a dual-convergence algorithm to speed up the computation. Second, the thesis proposes a fragmentation-free spatial allocation algorithm to explicitly model interdependency constraints among decision variables during optimization. Specifically, it introduces an optimization formulation with new spatial decision variables to model spatial contiguity and regularity constraints. It also proposes a hierarchical fragmentation elimination algorithm as well as a multi-layer integral image to efficiently solve the problem in a heuristic manner. Third, the thesis proposes a domain-knowledge assisted learning framework (i.e., TIMBER) to map geospatial objects (i.e., trees) with limited training data. The TIMBER framework introduces a geometric optimization formulation and a fast solver to generate candidates of tree-like structures for the deep learning model, which greatly reduces the difficulty of learning as well as the huge demand on training data. It also proposes a core object reduction algorithm to improve the computational performance. Extensive experiments and case studies show that the proposed approaches greatly outperform existing work in solution quality, and the proposed acceleration techniques greatly reduce the computational cost.
Image Enhancement Algorithms to Improve Robustness and Accuracy of Pre-trained Neural Networks for Autonomous Driving
(2023-01) Joshi, Himanshu
This research proposes a generalized data-driven approach for improving the pre-training image datasets fed to neural networks(NNs). The algorithms developed and tested in this work could substantially enhance the image bringing out the critical spatial information in the image for better NN performance. This image enhancement technique consists of two main components: image colorization and contrast enhancement. Image colorization is implemented to obtain a color-corrected image from a grayscale image. The traditional global contrast enhancement algorithm is extended to Smoothened Variable Local Dynamic Contrast Improvement (SVL-DCI) to boost local contrasts within an image frame that suffers from under/over-exposed lighting conditions. SVL-DCI algorithm is developed and thoroughly tested in the present thesis that could run in real-time as a pre-training algorithm for NNs. We implemented SVL-DCI on the 3P lab dataset of 2470 images and observed competitive improvement in the performance of the investigated NNs for object recognition and lane detection.
The length perception via dynamic touch with undefined inertia
(2013-08) Yoshida, Ken
Perception of object length arising from manual wielding is powerfully influenced by the inertia tensor of wielded objects (e.g., Solomon & Turvey, 1988). In solid objects the inertia tensor is a fixed quantity which can be computed, and whose responses to torques are stable. By contrast, when I lift a glass to drink, I am wielding (in addition to the glass) a liquid, whose dynamics (including the inertia tensor) vary as a function of movement. In this study I asked whether judgments of object length during manual wielding would be influenced by the presence of liquid mass in the wielded object. In Experiment 1, the type of weight was manipulated (liquid and solid weights). In Experiment 2, I manipulated the type of weight and movement of liquid by orienting the cylindrical weight horizontally or vertically. In both experiments, judgments of length were strongly correlated with the weight position, and changing dynamics of liquid weights did not reduce the accuracy of length perception. On the basis of these results I argue that the inertia tensor is not likely single unique mechanical information to be detected for the haptic length perception.
Measuring the Detection of Objects under Simulated Visual Impairment in 3D Rendered Scenes
(2018-09) Carpenter, Brent
A space is visually accessible when a person can use their vision to travel through the space and to pursue activities intended to be performed with vision within that space. Previous work has addressed the difficulty of evaluating the detection of objects in real spaces by observers with simulated visual impairments. This current research addresses the viability of using physically realistic 3D renderings of public spaces under artificially induced blur in place of the more resource intensive testing in the real spaces themselves while participants wear blurring goggles. In addition, this research illustrates the efficacy of a model that predicts portions of public scenes that an observer with simulated vision impairment would presumably fail to detect by comparing the predictions of missed space geometry to actual geometry detection failures by observers with simulated impairments. Lastly, this work also addresses how well simulated Low Vision observers can categorize the contents of scenes. Observer categorization rate is compared to several image metrics and the results indicate that average classification rate across Low Vision simulations can be predicted very well by knowing the averages of several different image metrics within each of the acuity blocks. Chapter 1 of this dissertation is a literature review necessary for understanding the background of the state of the art of this research and an overview of the research itself. In Chapter 2, an experiment is described in which object visibility was tested in a virtual environment with the goal of validating the use of 3D renderings as substitutive stimuli via comparing performance between the real and digital version of the same task (Bochsler et al., 2013). The objects were ramps, steps, and flat surfaces. Participants were normally sighted young adults who viewed either blurred or unblurred images. Images were blurred using a Gaussian filter on a Sloan Chart calibrated for the viewing distance of the experiment. Patterns of object identifications and confusions between the digital and physical versions of the task were highly similar. It is very likely that 3D renderings of public spaces when used in psychophysical tasks are effective substitutive stimuli for real spaces in object detection tasks. Avenues for parametric manipulations that might strengthen the argument are also explored. Chapter 3 extends the use of physics based 3D renderings to simulations of visual impairment (Thompson et al, 2017; https://github.com/visual-accessibility/deva-filter). A model of visual impairment was used to simulate 3D renderings of public spaces under increasing levels of impairment. Participants were then asked to draw the edges and contours of objects in these simulations under several separate task conditions: draw the edges of doors, stairs, obstacles, or floor-wall-ceiling connections. As simulations of visual impairment deepened, observers struggled to find the correct object contours in each of the tasks. Also, as the simulated impairments deepened, observer data often more closely matched the predictive model: a system that puts a premium on sudden changes in luminance contrast. In the absence of context and meaning, simulated Low Vision observers tend to make false positive geometrical edge identifications when a scene has non- accidental incidences of strong luminance contrast edges such as bars of light and shadows. The predictive power and utility of the model for simulating visual impairment is also discussed. Chapter 4 contains a pilot experiment which seeks to understand how well simulated Low Vision observers can classify the category of blurry scenes shown to them. Observers were asked to perform a three alternative forced choice task where they must identify if an image is one of three scenes, and observers’ classification accuracy was tracked across acuity level simulations. Several image metrics were calculated and regressed against classification accuracy of either single scenes or classification accuracy per acuity block. It was found that average classification accuracy within an acuity block could be predicted by knowing any one of several average image metrics of scenes within blocks and when regressed across acuity levels.
Perception of social loafing, Conflict, and emotion in the process of group development
(2013-08) Zhu, Min
This study was conducted for two purposes. The first was to find out trend patterns for perceived social loafing, the four types of intra-group conflict (i.e., task, relationship, logistic, and contribution), and positive vs. negative emotions, in the group's developmental process. The second was to explain how perceived social loafing was aroused based upon the knowledge of intra-group conflicts and negative emotions. Participants (n = 164) were required to report their personal perception of social loafing, intra-group conflicts, emotions (i.e., anger, fatigue, vigor, confusion, tension, depression, and friendliness), and the stage of group development, in their current small group interaction. Four major findings emerged out of the data analysis. First, perceived social loafing, relationship conflict, logistical conflict, contribution conflict, and negative emotions all followed a reversed V-shaped trend of development with their respective peaks observed at Stage 2 (i.e., Counterdependency and Fight), whereas task conflict followed a slanted, N-shaped, but relatively stable, trend over the course of group development. Second, positive emotions developed in a V-shaped trend pattern, wherein the lowest point was observed at Stage 2 and highest point at Stage 4 (i.e., Work). Third, the perception of social loafing was found to be directly and positively influenced by contribution conflict and negative emotions, while task conflict, logistical conflict, and relationship conflict did not have direct positive effects on perceived social loafing. However, task conflict was found to have a marginally significant direct suppressing effect upon perceived social loafing once the influences from logistic conflict, contribution conflict, relationship conflict and negative emotions were controlled for. Fourth, the current study also found that the perception of social loafing might not always trigger negative emotions in the group, because social compensation might offset the negative consequences that perceived social loafing was likely to bring to the group.
Perception of Waiting Time at Transit Stops and Stations
(Center for Transportation Studies, University of Minnesota, 2016-02) Fan, Yingling; Guthrie, Andrew; Levinson, David
Waiting time in transit travel is often perceived negatively and high-amenity stops and stations are becoming increasingly popular as strategies for mitigating transit riders’ aversion to waiting. However, beyond recent evidence that realtime transit arrival information reduces perceived waiting time, there is limited empirical evidence as to which other specific station and stop amenities can effectively influence user perceptions of waiting time. To address this knowledge gap, the authors conducted a passenger survey and video-recorded waiting passengers at different types of transit stops and stations to investigate differences between survey-reported waiting time and video-recorded actual waiting time. The authors employ regression analysis to explain the variation in riders’ reported waiting time as a function of their objectively observed waiting time, as well as station and stop amenities, while controlling for weather, time of day, personal demographics, and trip characteristics. Based on the regression results, most waits at stops with no amenities are perceived at least 1.3 times as long as they actually are. Basic amenities including benches and shelters significantly reduce perceived waiting times. Women waiting for more than 10 minutes in surroundings perceived to be insecure report waits as dramatically longer than they really are, and longer than do men in the same situation. The authors recommend a focus on providing basic amenities at stations and stops as broadly as possible in transit systems, and a particular focus on stops on low-frequency routes and in less safe areas for security measures.
Postural and cardiac responses to suprapostural tasks among children with and without developmental coordination disorder.
(2011-07) Chen, Fu-Chen
Developmental coordination disorder (DCD) is a diagnosis for children who present movement difficulties but are of normal intelligence without neurological deficits. Previous studies have preliminarily exploited postural and suprapostural task paradigm to research differences of motor characteristics between DCD and typically developmental children (TDC). However, to date no research has sought to investigate the postural and cardiac responses when performing perceptual-demanding and cognitive-demanding suprapostural tasks across task difficulties.The aim of the present investigation were to compare the effect of varying visual and memory demands of suprapostural tasks on postural motion and control of heart in children with DCD and TDC. Two groups of children (DCD and TDC) , aged between 9 and 10 years were recruited. They were instructed to execute a suprapostural visual and memory task with two difficulty levels, low difficulty (LD) and high difficulty (HD), separately while postural motion and cardiac activity were recording. Postural sway variability and cardiac parameters (HR, HF, LF/HF, sample entropy) were employed to determine motor and cardiac responses in corresponding to visual and memory tasks between DCD and TDC. Our findings demonstrated that (1) biomechanical and cardiac responses were less different between the two groups during suprapostural memory tasking, reflective of a comparable effect of suprapostural memory task on both groups, and (2) biomechanical and cardiac responses were significant different between DCD and TDC while engaging in suprapostural visual task, suggesting that TDC are capable of modulating postural motion to facilitate the goal of a visual demanding task but children with DCD are incapable.
Predicting face recognition skills in children: global processing and attention to the eyes
(2013-05) Corrow, Sherryse
Faces are, arguably, the most important stimulus in our lives. Yet, we understand very little about what information is used to recognize faces. Two theories exist in the literature on this topic. First, it is widely believed that successful face recognition depends on the ability to utilize configural, or holistic, information about the face. Second, many have speculated that attention to the eye region of the face is essential for successful face recognition. However, few studies, none with children, have directly evaluated this relationship by examining individual differences in face processing. Thus, the goal of the following studies was to examine how individual differences in face recognition skills are predicted by configural processing of the face and, in particular, attention to the eye region. Across four experiments, children completed face recognition tasks using an eye tracker, tasks of configural processing, and an object recognition task. Results from Experiments 1 and 2 support the notion that attention to the eye region and configural processing of faces as measured by the Part-Whole Task are predictive of face recognition scores as measured by the Cambridge Face Memory Task for Children. Furthermore, these experiments provide preliminary evidence that attention to the outer areas of the face, such as the forehead, may inhibit face recognition ability. Experiment 3 generally replicated these findings, with a few exceptions, by examining a pre-selected group of children and subsequently comparing high and low performers on the Cambridge Face Memory Task. Finally, Experiment 4 examined six children with developmental prosopagnosia. Results from this experiment suggest that children with prosopagnosia are a very heterogeneous group. The results of these studies generally support three hypotheses: 1. Children who demonstrate greater attention to the eye region perform better on tasks of face recognition, 2. Higher scores on tests of configural face processing predict higher scores on tasks of face recognition, and 3. Children who demonstrate a greater degree of configural face processing are more likely to attend to the eye region of the face (Experiment 2).
Representation of Human Body Stimuli within the Human Visual System
(2021-03) Bratch, Alexander
The human body is a unique and complex visual stimulus, the accurate representation of which is critical for social interaction/communication, acquisition of complex skills, and even basic survival. In a series of studies, using behavioral and neuroimaging techniques, the visual representation of some of the basic features of body perception (e.g., individual parts and their relationships) were explored. First, using a behavioral adaptation paradigm, sensitivity to the relative proportions between limbs was explored. We found that human observers were highly sensitive to relative limb proportion and further demonstrated that this effect appears to depend on body and limb specific mechanisms. Second, an fMRI experiment was used to assess the sensitivity of body-selective cortical areas to the spatial configuration of pairs of limb parts. We found that activity in body-selective areas systematically varies with the typicality of their spatial configuration. Finally, advanced sub-millimeter fMRI techniques were used investigate whether body-selective cortex contained subordinate representations of body stimuli (e.g., their individual parts). We found that the body-selective area of the right extrastriate cortex yields the highest responses to hands above all other stimuli. Furthermore, advanced spatial mapping techniques revealed that this cortical area contains spatially consistent clusters of voxels which preferentially respond to hands. Taken together, these results help to clarify how individual body parts and the relationships between them are represented within the human visual system.
Sociophonetic perception of African American English in Minnesota
(2014-05) Abdurrahman, Muhammad Ibn Abdullah
Although it can be authentically spoken by people who don't share their lineage, African American English, a variety of American English, is primarily spoken by the descendants of forced immigrants from Africa to North America. An assumption underlying most work on African American English (AAE) is that the variety is not subject to regional variation. Despite this assumption, some studies have found regional variation in AAE (Hinton and Pollock, 2000; Thomas, 2007). This variation is typically explained as assimilation toward or away from local varieties spoken by European Americans. Some studies have suggested that it assimilates with other dialects in less segregated areas or where blacks have greater access to educational opportunity (Hinton and Pollock, 2000). Other studies show that AAE speakers are less likely to produce mainstream regional variants and even less likely in cases of greater racial segregation (Labov and Harris 1986; Bailey, 2001.) This dissertation studies listeners' associations between regional variation and ethnicity. The study focuses on the influence of the regional features of Minnesota English on the perception of talker ethnicity. Hinton and Pollock (2000) begin their study of regional AAE phonology with the understanding that that the Midwest is less segregated than the south, and consider that this may imply that AAE in the Midwest is more likely to assimilate with regional European American varieties. Hence, we would predict that listeners in Minnesota would expect some tendency on the part of African Americans to use Minnesotan English (MNE) features, and hence said listeners would have little hesitation labeling speech containing Minnesotan variants as having been produced by European Americans even if it were produced by an African American. This study examined this topic with a perception experiment. Previous research has shown that listeners can ascertain a speaker's race from audio-only samples of content-neutral speech (Buck, 1968; Roberts, 1966; Walton and Orlikoff, 1994; Plichta, 2001; Thomas and Reaser, 2004). We examined listeners' judgments of the likelihood of particular speaker-listener comparisons. We paired the speech of African Americans and European Americans from Minnesota with pictures of African Americans and European Americans. We were particularly interested in whether listeners would be less likely to judge the speaker-picture pairs to be a match when the tokens contained variants that were characteristic of the 'mainstream' regional variety spoken in Minnesota, and the pictures were of African Americans. Listeners were more likely to rate actual matches between voice and face ethnicity as matches than they were to rate them as mismatches for male voices, but not for female ones. The unwillingness to rate voices produced by European Americans with local Minnesotan features as matches to African American faces suggests that listeners do not believe the local variant of AAE to incorporate Minnesota English features, at least for male speakers. Implications for models of sociophonetic perception and for studies of variation in AAE are discussed.
Spaciousness & preference: a study in the perception of density in the suburban residential built environment
(2013-06) Lilli, Erin Elizabeth
As the country's population increases, it is worth determining what types of residential settings people currently residing in the low density suburbs environments would prefer- simply because those environments would need to increase their density to mitigate sprawl. To inform the creation of high density residential living, this study seeks to identify specific characteristics of a dense settlement most acceptable to people wanting suburban living. Residential suburban communities, as in the United States, often have low dwelling unit densities, as antidote to the congestion and crowding of the urban core environment. Primarily consisting of single family homes on individual plots of land with private yards and wide streets; these developments are becoming more ubiquitous despite the role of both the automobile and land conversion as major contributors to the high concentrations of carbon dioxide in the atmosphere. The question this study asks is, `what residential physical and spatial configurations are a preferred environmental quality and/or are perceived as low density by people currently living in low density suburban environments?' In other words, can we design a desirable environment that is perceived as low density, while actually utilizing less land area, thus being denser than existing low density counterparts? To investigate this question four residential elements (housing typologies street width, set back depth, and tree coverage) were systematically configured in images of a street scene. These images were the subject of a survey sent to 400 randomly selected inhabitants of Beaverton, Oregon who were asked to choose the images they felt were the most spacious and most preferred from a sets of scenes using discrete choice modeling. Results indicated that the strongest predictors of preference and spaciousness lie in the relationship between tree coverage and setback depth- thus the areas where housing design may be used to increase density.
Temporal and spatial properties of the BOLD fMRI response to first and second order contrast in V1.
(2010-01) Thompson, Serena Kainoa Au
Our ability to detect, discriminate, and identify objects, to extract depth information through the use of stereopsis, and to learn about and classify different surface properties and textures are all secondary to first extracting useful cues about the local contrast within a visual scene. Contrast can be made by a change in a variety of visual features. We will specifically consider the contrast made by first-order and second-order luminance changes, specifically the contrast between local pixel luminance, and the contrast between local pixel luminance variance. There are a variety of tools available to `observe' cortical modulation to contrast, such as electrophysiological recordings of spike rate or local field potentials, fMRI BOLD modulation, magnetic encephalography (MEG), or visually evoked potentials (VEP), or through behavioral markers such as detection thresholds and discrimination thresholds. BOLD fMRI modulation provides a unique tool to measure the early visual response to local changes in image contrast with superior spatial specificity and minimal subject invasiveness, while psychophysics allows us to quantify the information human observers use to detect contrast. We will use both BOLD fMRI and psychophysics to explore three components of the human response to contrast: 1) how much do we use contrast when it forms the edge of a target shape compared to when it composes the interior area of the shape; 2) how well does second-order contrast modulate early visual cortex compared to the modulation elicited by first-order contrast; and 3) how accurate is the timing information of functional magnetic resonance imaging (fMRI) of the blood oxygen-level dependent (BOLD) modulation. Human observers do not always use contrast in the same way, and in the first experiment we study how human observers use first-order contrast in an image region versus second-order contrast at a region boundary when accomplishing a difficult detection task. We may expect V1 response to differ when contextual cues suggest that contrast is contained within an object border compared to when it fills in the interior texture of an object. Consider the case of two Holstein (black and white spotted) cows standing together, one partially occluding the other. We can use contrast cues to both identify which parts belong to which cow, as well as to determine the type of cow based on the spotted character of its hide. Both the segmentation task and the identification task require use of the same type of contrast information. However, optimal processing may change the way that low-level cues are handled in early visual cortex by modulation through context-dependent feedback as well learned information about cows. This may give rise to similar low-level cues producing different neural signals in early cortical areas, and subsequently, different sensitivity to cues in a border compared to a region. Our first experiment explores observers' use of contrast contained within the edge of a detectable target compared to the contrast that makes up the entire interior region of the target. Extraction of local image contrasts occurs at an early stage of visual processing, however, which types of contrast and how strongly they modulate early visual cortex remains undetermined. There are a variety of contrasts that could be compared. The first-order versus second-order contrast comparison is appealing because, with images generated by locally changing either average pixel luminance or pixel variance in white noise, we can create stimuli that are equal in orientation and spatial frequency information, contain detectable boundaries, and still require independent information to be extracted for detection. Our second experiment quantifies the response in primary visual cortex (V1) to first- and second-order using fMRI to acquire a spatially specific edge response in human subjects. Finally, it would be ideal to acquire both spatially and temporally specific measurements of cortical modulation in response to contrast changes. Several research groups around the world have begun using the relative timing between BOLD fMRI events to assign causal significance to the temporal order of modulation across different cortical areas using dynamic causal modeling. If, however, the timing of the modulation depends on the strength of the modulation, we could draw false conclusions from relative timing comparisons. Therefore, in our third experiment we measured three temporal characteristics of the BOLD hemodynamic response function (HRF) as a function of stimulus contrast: onset latency, time to peak, and full-width half-maximum. These explorations into the human and BOLD fMRI response to contrast are aimed at developing the current knowledge about how we perceive and parse the world around us, as well as how we can better interpret one of our measurement tools, fMRI, as a correlate of the neuronal activity occurring in early visual cortex. Both aims guide us toward a better understanding of the mechanisms we employ to process the rich information our visual systems acquire.
Travel time perception errors: causes and consequences
(2013-07) Carrion, Carlos
This dissertation contributes novel results to the following areas of transportation research: travel time perception; valuation of travel time; and route choice modeling. This study presents a systematic identification of factors that lead to perception errors of travel time. In addition, the factors are related to similar factors on time perception research in psychology. These factors are included in econometric models to study their influence on travel time perception, and also identify which of these factors lead to overestimation or underestimation of travel times. These econometric models are estimated on data collected from commuters recruited from a previous research study in the Minneapolis-St. Paul region. The data (surveys, and Global Positioning System [GPS] points) consists of work trips (from home to work, and from work to home) of subjects. For these work trips, the subjects' self-reported travel times, and the subjects' travel times measured by GPS devices were collected. Furthermore, this dissertation provides the first empirical results that highlight the influence of perception errors in the valuation of travel time, and in the dynamic behavior of travelers' route choices. Last but not least important, this dissertation presents the most comprehensive literature review of the value of travel time reliability written to date.
Understanding Post-COVID Safety Concerns Toward the Use of Transit and Shared Mobility in Greater Minnesota
(Minnesota Department of Transportation, 2023-04) Ryan, Galen; Fan, Yingling; Qian, Xinyi; Linscheid, Neil
This study investigates the perceived safety risks and barriers that might prevent transit and shared mobility services from attracting post-COVID riders in Greater Minnesota. It includes an online survey of Greater Minnesota residents to understand their COVID-related safety concerns and their preferences and perceptions toward existing and potential safety protocols. The survey results show that, during the post-COVID era, driving alone continues to dominate, but desires to use transit and shared mobility modes remain strong. Lack of access, lack of interest, and lack of available better alternatives jointly affect transit-use behavior. Women, people with COVID concerns, urban residents, online shoppers, and transit users are associated with stronger preferences toward COVID safety measures. People with COVID concerns, online shoppers, and transit users are also associated with preferences toward general transit service improvements. We also find that elderly people, hesitant tech users, and transit-dependent users are unlikely to be positively affected by trip-planning tools and contactless payment technology. Furthermore, income and car ownership predict future transit use, and younger age is associated with more interest in carpooling. These results help to inform transit and shared mobility providers about what safety and communications strategies will be most effective in bringing users back.
When is physical attractiveness not beneficial? Perceptions of warmth and competence, emotions, and job behaviors.
(2015-07) Mehng, Si Ahn
Diverging from the dominant positive view of physical attractiveness, I propose that attractive individuals at times experience negative outcomes at work. Research substantiates that judgments of competence and warmth combine to affect perceivers' emotional and behavioral reactions to target individuals. Attractive individuals are perceived as highly competent, but not necessarily highly warm. Perceived warmth moderates the effects of competence on emotional and behavioral responses to targets. Thus, although attractive individuals may elicit positive responses (e.g., admiration, altruistic helping) if perceived as highly warm, they may elicit negative responses (e.g., envy, workplace aggression) if perceived as lacking warmth. I used a laboratory experiment and a field study to test the theoretical model. Given some aspects of the study design and data, it is hard to be conclusive regarding the study findings. However, the laboratory study found support for the positive relationship between physical attractiveness and perceived competence, and some support for a negative relationship between physical attractiveness and job behaviors when the perceived warmth was low.

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