Browsing by Author "Johnson, Elizabeth"

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    A long-term temporal analysis of heavy metal concentrations in seabird feathers with implications for overgeneralized trophic dynamics
    (2019-04-26) Johnson, Elizabeth
    Anthropogenic deposition and natural cycling of heavy metal can impact ecosystem function: They can accumulate in marine sediment layers and remain there for long periods of time. As these metals accumulate and move through the ecosystem to higher trophic level organisms, these metals have known toxic effects including decreased reproductive success and compromised immune systems. Seabird feather levels may be representative of broader ecosystem signals and heavy metal cycling. This study combines heavy metal concentration data from seabird feathers and builds on the results of previous studies looking at trophic declines across time. The aim is to emphasize the importance of tracking trophic levels of top predators, looking at heavy metal concentrations from the 1880s to 2016, as well as carbon and nitrogen stable isotopes to determine if changing trophic levels will alter estimated trends and environmental heavy metal concentrations. We present temporal trends in seabird tissue concentration, and examine the complex field of trophic transfer, proposing a protocol for interpreting environmental concentrations. Our results show that trophic declines do not drastically impact directional trends, but that extrapolating to other trophic levels creates a large margin of uncertainty. We observe declines in heavy metals that correspond with relevant legislation, and suggest further studies into lesser known metals to strengthen environmental monitoring methods.
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    The Role of Color in Face Processing and Autism Spectrum Disorders
    (2017-05-04) Katz, Sophie
    The contribution of color in relation to face processing is poorly understood, despite the critical role of face processing in adaptive human interaction and social communication. Both faces and color are particularly salient cues necessary for navigating the environment. This project examines how the typical fixation behaviors employed for face processing are affected by the removal of color. Previous studies using eye-tracking have predominantly used achromatic stimuli, ignoring the role of color in face perception. Furthermore, given that face processing is disrupted in Autism Spectrum Disorders (ASD), investigation into how gaze behavior is affected by color in relation to ASD symptoms is critical to understanding the nature of observed deficits in social communication. We use the Broad Autism Phenotype Questionnaire (BAPQ) to explore the contribution of ASD-related behaviors in a neuro-typical population. Results indicate that the removal of color from images of faces is associated with increased fixation on the eyes of grayscale faces over normal, color faces. Exploratory correlations with BAPQ scores reveal that this tendency is enhanced in subjects with higher (more ASD-like) scores than that those with lower scores, suggesting that color provides social information that influences overall fixation time on the eyes.