Metaphors Matter: Top-Down Effects on Anthropomorphism

Anthropomorphism, or the attribution of human mental states and characteristics to non-human entities, has been widely demonstrated to be cued automatically by certain bottom-up appearance and behavioral features in machines. In this thesis, I argue that the potential for top-down effects to influence anthropomorphism has so far been underexplored. I motivate and then report the results of a new empirical study suggesting that top-down linguistic cues, including anthropomorphic metaphors, personal pronouns, and other grammatical constructions, increase anthropomorphism of a robot. As robots and other machines become more integrated into human society and our daily lives, more thorough understanding of the process of anthropomorphism becomes more critical: the cues that cause it, the human behaviors elicited, the underlying mechanisms in human cognition, and the implications of our influenced thought, talk, and treatment of robots for our social and ethical frameworks. In these regards, as I argue in this thesis and as the results of the new empirical study suggest, the top-down effects matter

Top-down effects on early visual processing in humans: a predictive coding framework

An increasing number of human electroencephalography (EEG) studies examining the earliest component of the visual evoked potential, the so-called C1, have cast doubts on the previously prevalent notion that this component is impermeable to top-down effects. This article reviews the original studies that (i) described the C1, (ii) linked it to primary visual cortex (V1) activity, and (iii) suggested that its electrophysiological characteristics are exclusively determined by low-level stimulus attributes, particularly the spatial position of the stimulus within the visual field. We then describe conflicting evidence from animal studies and human neuroimaging experiments and provide an overview of recent EEG and magnetoencephalography (MEG) work showing that initial V1 activity in humans may be strongly modulated by higher-level cognitive factors. Finally, we formulate a theoretical framework for understanding top-down effects on early visual processing in terms of predictive coding

Top-down effects on compensation for coarticulation are not replicable

Listeners use lexical knowledge to judge what speech sounds they heard. I investigated whether such lexical influences are truly top-down or just reflect a merging of perceptual and lexical constraints. This is achieved by testing whether the lexically determined identity of a phone exerts the appropriate context effects on surrounding phones. The current investigations focuses on compensation for coarticulation in vowel-fricative sequences, where the presence of a rounded vowel (/y/ rather than /i/) leads fricatives to be perceived as /s/ rather than /∫/. This results was consistently found in all three experiments. A vowel was also more likely to be perceived as rounded /y/ if that lead listeners to be perceive words rather than nonwords (Dutch: meny, English id. vs. meni nonword). This lexical influence on the perception of the vowel had, however, no consistent influence on the perception of following fricative.peer-reviewe

Top Down Effects and Resource Selection by Coyotes in South Carolina

Top predators play important roles in functioning ecosystems, including regulating the populations of prey species and competing with other predators. However, in the face of global change, many top terrestrial predators have declined in both range and abundance, making room for some smaller predators to expand into new niches. Coyotes (Canis latrans) in North America are a prime example of this – they have rapidly expanded their range in the last 120 years, raising concerns about their impacts on both domestic and wild species. In eastern North America, research has centered around their effects on white-tailed deer (Odocoileus virginianus), which are an important game species and particularly vulnerable to coyotes during the first few weeks of life. Despite efforts by governments and citizens to kill coyotes across much of their new range, they are now established, and managers are looking for ways to quantify and reduce their effects on native species. Critical questions remain about variability within coyote populations and how exactly they respond to temporary foods on the landscape. To address these questions, we studied coyote spatial and community ecology in the Piedmont region of South Carolina, USA. In Chapter 1, we used GPS data to investigate variability in habitat selection and movement. At the population level, coyotes avoided risky areas (i.e., open and developed habitat), especially during risky times. However, we found differences across seasons, behavior states, and sexes, highlighting the importance of both extrinsic and intrinsic factors in predicting movement. In Chapter 2, we quantified coyote diet, focusing on the summer months when fawns were available. Coyotes largely switched to temporarily available foods during the summer and fall, suggesting that alternative foods (i.e., summer fruits) could buffer predation on fawns. In addition, using genetics, we found that most of the individuals in our population switched to these temporary foods, indicating that targeted removal would likely not decrease fawn mortality. In Chapter 3, we investigated whether coyotes changed their foraging tactics for different foods and also described coyote movement surrounding fawn predation events. We compared foraging patterns for fawns, blackberries, and small mammals and found relatively few differences in when and how coyotes moved, yet differences in where they foraged. Linking fawn predation events to coyote GPS data showed that coyotes tended to move relatively fast and linearly prior to killing a fawn, then would quickly move away from the kill site and rest for several hours. In Chapter 4, we broadened our investigation into top-down effects by using a field manipulation to test how coyotes influenced smaller carnivore scavenging behavior, relative to other hypothesized factors. We found that coyotes only directly influenced bobcat behavior, while forest structure (particularly understory cover) seemed to modulate risk from coyotes, highlighting the complexity of interactions among carnivores. Taken together, our findings highlight that 1) coyotes have diverse, yet context-dependent top-down effects and that 2) temporary foods shape their behavior and diet (particularly in the summer). More broadly, our findings suggest that habitat management which promotes alternative foods and accounts for human shields may be a viable strategy to influence the behavior of large-herbivore predators. Generalist carnivores will likely continue to thrive in the Anthropocene, necessitating continued research into their effects on other species and management strategies to best coexist

Mammal predator and prey species richness are strongly linked at macroscales

Predator-prey interactions play an important role for species composition and community dynamics at local scales, but their importance in shaping large-scale gradients of species richness remains unexplored. Here, we use global range maps, structural equation models (SEM), and comprehensive databases of dietary preferences and body masses of all terrestrial, non-volant mammals worldwide, to test whether (1) prey bottom-up or predator top-down relationships are important drivers of broad-scale species richness gradients once the environment and human influence have been accounted for, (2) predator-prey richness associations vary among biogeographic regions, and (3) body size influences large-scale covariation between predators and prey. SEMs including only productivity, climate, and human factors explained a high proportion of variance in prey richness (R2 = 0.56) but considerably less in predator richness (R2 = 0.13). Adding predator-to-prey or prey-topredator paths strongly increased the explained variance in both cases (prey R2 = 0.79, predator R2 = 0.57), suggesting that predator-prey interactions play an important role in driving global diversity gradients. Prey bottom-up effects prevailed over productivity, climate, and human influence to explain predator richness, whereas productivity and climate were more important than predator top-down effects for explaining prey richness, although predator top-down effects were still significant. Global predator-prey associations were not reproduced in all regions, indicating that distinct paleoclimate and evolutionary histories (Africa and Australia) may alter species interactions across trophic levels. Stronger crosstrophic- level associations were recorded within categories of similar body size (e.g., large prey to large predators) than between them (e.g., large prey to small predators), suggesting that mass-related energetic and physiological constraints influence broad-scale richness links, especially for large-bodied mammals. Overall, our results support the idea that trophic interactions can be important drivers of large-scale species richness gradients in combination with environmental effects. © 2013 by the Ecological Society of America

Omnivory and periphyton mats: uncoupling and quantifying consumer effects in the Florida Everglades

The role of omnivores in structuring communities is poorly understood. I studied the effect of two abundant omnivores, grass shrimp (Palaemonetes paludosas) and eastern mosquitofish (Gambusia holbrooki), on periphyton biomass of the Florida Everglades. I performed field experiments to test for consumer top-down and “complex” top-down effects on periphyton biomass. My experiments suggested that shrimp and mosquitofish had consumptive effects on periphyton but in many instances, periphyton wet weight, AFDM, and chlorophyll a increased significantly with shrimp or fish density, suggesting compensation by nutrient regeneration or trophic cascade processes. I propose that characteristic periphyton mat structure and integrity deters herbivory and affects the outcome of the periphyton-consumer interaction. Results from a descriptive study and a laboratory experiment support this hypothesis. Overall, consumption by shrimp and mosquitofish was significant, but coupled with and sometimes compensated by “complex” top-down effects, making these consumers “functional” omnivores

Eastern Red-backed Salamanders Regulate Top-Down Effects in a Temperate Forest-Floor Community

Understanding the role of species interactions as regulatory mechanisms for ecosystem processes presents a challenge to ecologists working in systems with high species diversity and habitat complexity. Recent studies suggest that interactions among intraguild predators, such as terrestrial salamanders and large arthropods, might be important for the regulation of detritivores, fungivores, and perhaps detritus within terrestrial webs. A key prediction is that interactions among predators weaken trophic cascades. Our research examined this prediction by removing predators for 4 yr from unfenced field plots to investigate the effects on litter arthropods, the microbial community, and rates of leaf litter decomposition. We manipulated predator abundance in three treatments (salamander removal, centipede removal, and multiple predator removal) compared to a control in which no predators were removed. Despite difficulties in suppressing centipede numbers, we observed increases in salamanders, millipedes, isopods, slugs, numbers of ant colonies, and gamasid mites in the centipede removal plots. Additionally, several phospholipid fatty acid markers for bacteria were suppressed in plots where salamanders were most abundant. Finally, we detected treatment effects on the rate of litter disappearance from leaf bags in our field plots: those with the most salamanders had the lowest levels of litter decomposition. Overall, we found some evidence for top-down effects of predators in a temperate forest-floor web. Our study is one of few that have employed an unfenced field design and the only study examining the effects of salamanders on forest soil microbes. The results contribute to a growing body of evidence indicating that territorial predators, such as terrestrial salamanders, can be strong regulators of species composition at lower trophic levels in a system that is commonly thought to be regulated primarily through bottom-up effects of organic matter supply

Bottom-up and top-down effects of browning and warming on shallow lake food webs

Productivity and trophic structure of aquatic ecosystems result from a complex interplay of19 bottom-up and top-down forces that operate across benthic and pelagic food web compartments.20 Projected global changes urge the question how this interplay will be affected by browning21 (increasing input of terrestrial dissolved organic matter), nutrient enrichment and warming. We22 explored this with a process-based model of a shallow lake food web consisting of benthic and23 pelagic components (abiotic resources, primary producers, grazers, carnivores), and compared24 model expectations with the results of a browning and warming experiment in nutrient-poor25 ponds harboring a boreal lake community. Under low nutrient conditions, the model makes three26 major predictions. (1) Browning reduces light and increases nutrient supply; this decreases27 benthic and increases pelagic production, gradually shifting productivity from the benthic to the28 pelagic habitat. (2) Because of active habitat choice, fish exert top-down control on grazers and29 benefit primary producers primarily in the more productive of the two habitats. (3) Warming30 relaxes top-down control of grazers by fish and decreases primary producer biomass, but effects31 of warming are generally small compared to effects of browning and nutrient supply.32 Experimental results were consistent with most model predictions for browning: light penetration,33 benthic algal production, and zoobenthos biomass decreased, and pelagic nutrients and pelagic34 algal production increased with browning. Also consistent with expectations, warming had35 negative effects on benthic and pelagic algal biomass and weak effects on algal production and36 zoobenthos and zooplankton biomass. Inconsistent with expectations, browning had no effect on37 zooplankton and warming effects on fish depended on browning. The model is applicable also to38 nutrient-rich systems, and we propose that it is a useful tool for the exploration of the39 consequences of different climate change scenarios for productivity and food web dynamics in40 shallow lakes, the worldwide most common lake type.Fil: Rivera Vasconcelos, Francisco. Umea University. Department of Ecology and Environmental Science; SueciaFil: Diehl, Sebastian. Umea University. Department of Ecology and Environmental Science; SueciaFil: Rodriguez, Patricia Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Hedström, Per. Umea University. Department of Ecology and Environmental Science; SueciaFil: Karlsson, Jan. Umea University. Department of Ecology and Environmental Science; SueciaFil: Byström, Pär. Umea University. Department of Ecology and Environmental Science; Sueci

Animal water balance drives top-down effects in a riparian forest-implications for terrestrial trophic cascades

Despite the clear importance of water balance to the evolution of terrestrial life, much remains unknown about the effects of animal water balance on food webs. Based on recent research suggesting animal water imbalance can increase trophic interaction strengths in cages, we hypothesized that water availability could drive top-down effects in open environments, influencing the occurrence of trophic cascades. We manipulated large spider abundance and water availability in 20 × 20 m open-air plots in a streamside forest in Arizona, USA, and measured changes in cricket and small spider abundance and leaf damage. As expected, large spiders reduced both cricket abundance and herbivory under ambient, dry conditions, but not where free water was added. When water was added (free or within moist leaves), cricket abundance was unaffected by large spiders, but spiders still altered herbivory, suggesting behavioural effects. Moreover, we found threshold-type increases in herbivory at moderately low soil moisture (between 5.5% and 7% by volume), suggesting the possibility that water balance may commonly influence top-down effects. Overall, our results point towards animal water balance as an important driver of direct and indirect species interactions and food web dynamics in terrestrial ecosystems

Bottom-Up and Top-Down Controls on Food Webs in Headwater Streams

Headwater streams account for 70% of stream channel length in the USA and are important as hotspots of nutrient uptake and native biodiversity. Biofilm, the mixed auto- and heterotrophic microbial community covering stream substrates, is where the majority of nutrient processing occurs, and forms the base of stream food webs, particularly in heavily shaded, oligotrophic streams. Both bottom-up (e.g., nutrients, light) and top-down (i.e., consumption) processes are known to affect periphyton, the autotrophic component of biofilm, but little is known about what controls the biofilm community as a whole. Top-down effects are common in streams, where fish are often the top predator and can cause cascading effects. However, salamanders – not fish – are the top predators in many small headwater streams, and the top-down effects of salamanders on stream food webs have received much less attention. I used experimental and observational approaches to investigate the role of top-down and bottom-up controls on headwater stream food webs. Specifically, I used stream mesocosms with two salamander species, Eurycea bislineata and Gyrinophilus porphyriticus, alone or in combination, to test the effects of salamander community composition on benthic and emergent macroinvertebrate density, biomass and community composition. To assess the relative importance of bottom-up and top-down determinants of biofilm biomass, I used a combination of stream surveys and pre-existing stream chemistry data from across the oligotrophic headwater streams of the Hubbard Brook Experimental Forest (HBEF). My experiment showed that stream salamanders alter benthic macroinvertebrate densities, but only when G. porphyriticus occurs alone, as it consumes E. bislineata, the smaller species, when it is present. This intraguild predation removes the top-down effects of G. porphyriticus on benthic macroinvertebrates. In my stream surveys, bottom-up variables (i.e., aspect, canopy cover, nutrients and pH) determined biofilm biomass, not salamander occupancy or benthic macroinvertebrate biomass. However, I did not encounter streams with the specific salamander community (i.e., G. porphyriticus present and E. bislineata absent) shown to produce top-down effects in my experimental study. My results demonstrate that salamanders can exert top-down control on benthic macroinvertebrate communities. This effect is, however, dependent on the salamander species present, and can be removed by intraguild interactions between salamander species. Furthermore, bottom-up factors, in particular light, appear to play the primary role in determining biofilm biomass. Despite prior evidence for the dominance of heterotrophic microbes in biofilms at the HBEF, the importance of light in controlling biofilm biomass suggests that the autotrophic component of these biofilms may be disproportionately important, and emphasizes the importance of understanding both the auto-and heterotrophic components of stream biofilms. My work links the rich history of research on stream salamander community ecology to broader studies of stream food webs, providing new avenues for future research