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The degradation of soil quality due to anthropogenic causes is globally important, both in terms of ecosystem services and ecological biodiversity. Soil quality reduction is stated to be detrimental for population densities and species diversity of soil invertebrates, including the mesofauna (Acari and Collembola). Within the soil food web, mesofauna occupy several trophic levels and as such facilitate nutrient turnover, fulfilling vital ecosystem functions and services. Understanding soil invertebrate population dynamics not only during degradation, but equally upon ecosystem restoration, is vital to identify possible losses or benefits to healthy ecosystem functioning. Prior to this investigation the Highfield site, Rothamsted Research, had been divided and maintained as grassland, arable cropping or bare fallow for 50 years. The latter resulted in a soil that had low soil organic matter levels, poor structure, low bacterial biomass and virtually no invertebrate population. Investigations into the invertebrate population changes, within both the experimental plots and surrounding land, upon alteration of the existing management strategies was completed over a two year period. Changes to mesofaunal populations were detected across all treatments following conversion. Generally, new fallow and arable management strategies produced low density fluctuating populations affected by the physical disturbance of ploughing and lack of soil organic matter as a basal food resource. Grassland management produced increased species diversity and abundance within a more stable soil food web. Each of the new management strategies developed towards its equivalent management strategy within the control treatments. Although it was apparent that the mesofaunal populations were re-establishing under more favourable environmental conditions, there was no definitive conclusion as to the source of the population increases. An attempt to identify the physical mode of invertebrate movement was completed, utilising a prototype mesocosm to act as a physical barrier, this showed promise for future use in such studies.

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The central challenge in face recognition lies in understanding the role different facial features play in our judgments of identity. Notable in this regard are the relative contributions of the internal (eyes, nose and mouth) and external (hair and jaw-line) features. Past studies that have investigated this issue have typically used high-resolution images or good-quality line drawings as facial stimuli. The results obtained are therefore most relevant for understanding the identification of faces at close range. However, given that real-world viewing conditions are rarely optimal, it is also important to know how image degradations, such as loss of resolution caused by large viewing distances, influence our ability to use internal and external features. Here, we report experiments designed to address this issue. Our data characterize how the relative contributions of internal and external features change as a function of image resolution. While we replicated results of previous studies that have shown internal features of familiar faces to be more useful for recognition than external features at high resolution, we found that the two feature sets reverse in importance as resolution decreases. These results suggest that the visual system uses a highly non-linear cue-fusion strategy in combining internal and external features along the dimension of image resolution and that the configural cues that relate the two feature sets play an important role in judgments of facial identity.

Everyday speech perception frequently occurs in degraded listening conditions, against a background of noise, interruptions and intermingling voices. Despite these challenges, speech perception is remarkably successful, due in part to perceptual learning. Previous research has demonstrated more rapid perceptual learning of acoustically-degraded speech when listeners are given the opportunity to map the linguistic content of utterances, presented in clear auditory form, onto the degraded auditory utterance. Here, I investigate whether learning is further enhanced by the provision of naturalistic facial gestural information, presented concurrently with either the clear auditory sentence (Experiment I), or with the degraded utterance (Experiment II). Recorded materials were noise-vocoded (4 frequency channels; 50- 8000 Hz). Noise-vocoding (NV) is a popular simulation of speech transduced through a cochlear implant, and 4-channel NV speech is difficult for naïve listeners to understand, but can be learned over several sentences of practice. In Experiment I, each trial began with an auditory-alone presentation of a degraded stimulus for report (D). In two conditions, this was followed by passive listening to either the clear spoken form and then the degraded form again (condition DCD), or the reverse (DDC); the former format of presentation (DCD) results in more efficient learning (Davis et al, 2005). Condition DCvD was similar to DCD, except that the clear spoken form was accompanied by facial gestural information (a talking face). The results indicate that presenting clear audiovisual feedback (DCvD) does not confer any advantage over clear auditory feedback (DCD). In Experiment II, two groups received a degraded sentence presentation with corresponding facial movements (Dv); the second group also received a second degraded (auditory-alone) presentation (DvD). Two control conditions and a baseline DCvD condition were also tested. Although they never received clear speech feedback, performance in the DvD group was significantly greater than in all others, indicating that perceptual learning mechanisms can capitalize on visual concomitants of speech. The DvD group outperformed the Dv group, suggesting that the second degraded presentation in the DvD condition further facilitates generalization of learning. These findings have important implications for improving comprehension of speech in an unfamiliar accent or following cochlear implantation. / Thesis (Master, Psychology) -- Queen's University, 2011-09-01 16:50:58.923

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