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A central feature of language is the ability to generalise beyond our previous experience to understand unfamiliar input and produce novel sentences (Hockett & Hockett, 1960). It is suggested that thematic roles support this ability by labelling the participants of an event with functions such as the agent and patient (Jackendoff, 1972). However, the nature of these roles is unclear, as language-based theories (e.g., Dowty, 1991) have often relied upon abstract conceptual features that are difficult to define or are not always available in the input. Yet, connectionist models of language have been unable to demonstrate systematic behaviour without including such role variables (Chang, 2002). This thesis aimed to address this issue by considering whether thematic roles in language are supported by the visual system, which allows viewers to track multiple objects in parallel (Pylyshyn & Storm, 1988) and identify their roles in causal events from their movement features (Scholl & Tremoulet, 2000). To test this connection, a total of nine experiments were conducted with adult participants using a modified version of the multiple object tracking paradigm. In this task, pairs of white circles engaged in causal push events. The participants were required to track the visually indistinguishable targets from these push events while they moved in random patterns for a short period, before producing a sentence to describe their interaction. Chapter 1 provides an introduction to these experiments. The function of thematic roles in reaching abstract representations of language is discussed, as well as issues with current theories regarding the nature of these roles. The visual perception of causality and the psychophysical features underpinning these impressions is presented as a potential solution, followed by a summary of the multiple object tracking literature. Chapter 2 reports the first three experiments of the thesis, which collectively provide evidence that the multiple object tracking system can support agent and patient features, even when the attentional demands of the task are manipulated. These studies found that the participants were able to retain the target identities to produce transitive sentences at test that accurately labelled the agent and patient of the interaction. Chapter 3 presents the results of a further six experiments, which used the same multiple push tracking task to examine the processing asymmetry between subject-extracted and object-extracted relative clauses (Gordon & Lowder, 2012). Here, the participants tracked visually identical targets that played the same role in two pushes or switched roles between the events. The results of these six experiments showed that visual events with consistent role-referent bindings are easier to retain and describe in language than those with no repetition or inconsistent bindings. This suggests that subject-extracted relative clauses may be easier to process since the subject referent plays the same role in both events. It also indicates that non-linguistic processing may contribute to the relative clause asymmetry, as the effect was observed when the studies also varied the sentence structures the participants used to describe the events. Finally, chapter 4 discusses the implications of these findings and whether thematic roles are supported by multiple object tracking in vision.

Composition, the conscious arrangement of elements within a visual image, is an important principle in art and is thought to be an integral component in eliciting affective aesthetic responses in judgments and appreciation of art. In this thesis I present four studies that give significant new insights on how human aesthetic preference for visual art is affected by compositional lateral asymmetries, and intrinsic factors such as symmetry, complexity and movement. Chapter 1 introduces the theoretical foundations of aesthetic preference and composition as context for the research, followed by an overview of the chapters, methodology and main findings. The research is divided into two main areas. Chapters 2-3 explore preferences in nonexperts for symmetries and lateral asymmetries in static images (novel abstract patterns and photographic self-portraits). Chapters 4-5 analyse asymmetrical biases in cinema films. Chapter 2 revisits previous research on British and Egyptian symmetry preferences using novel abstract patterns, and measurements of complexity. Findings supported a degree of universality for symmetry preference, but some differences in preferences for complexity. Chapter 3 examines whether previously reported preferences for a right-facing bias in painted self-portraits generalise to self-portraits by untrained subjects. Findings confirmed a similar bias, thus supporting a biological basis for side biases. Chapter 4 assesses whether mirror reversal of films affects viewer preference. Viewers did not detect the reversal of the film, but a composition specific exposure effect was observed in those who watched the original version. In Chapter 5, an analysis of posing position and orientation in film actors confirmed an inward-facing bias, a preference for left-to-right directionality in movement, but no left cheek bias. A trend implicated the influence of reading direction in the Egyptian data. Overall these findings confirmed some known preferences in direction and side biases in static and moving images, and provide new evidence in support of a biological basis for side biases independent of expertise. Importantly, they highlight some cultural differences in preferences for compositional symmetries that may be linked to reading direction, and a difference in preference for complexity. Defining what factors relating to composition determine preference is key to understanding human aesthetic preference and decisions in the appreciation and production of visual art. This thesis provides a significant contribution towards that goal.

Contour curvature information has been shown to have an impact on the visual perception of shape. We have conducted studies on perception of convexity and concavity in relation to memory and attention. Previous studies (Badcock & Westheirner, 1985; Krose & Julesz, 1989; Nakayama & Mackeben, 1989) have proposed that visual space is influenced by corners. Recent studies by Cole, Burton and Gellatly (2001) found that reaction times were faster for a stimulus located in the region of a corner of a figure. Cole et al (2001) believe that the role of corners is greater than that of straight edges, due to corners receiving a higher distribution of attentional resources relative to straight edges. The first part of this thesis considers the role figure-ground plays in the corner enhancement effect. Results demonstrate that the corner enhancement effect is only found when the probe is presented on the surface that owns the corner. Thus the corner enhancement effect is present for both concave and convex vertices. However, the effect disappears when the probe lay on the surface that does not own the corner. The second series of experiments made use of a shape with multiple concave or convex features as part of a change detection task, in which only a single feature could change. The results provided no evidence to suggest that convexities are special in visual short-term memory. Though coding of convexities as well as concavities provided a small advantage over an isolated contour. This finding is in accordance with the well documented effect of closure on shape processing (Elder & Zucker, 1993). It has been reported that deviations from symmetry were easier to detect when carried by convexities compared to deviations carried by concavities (Hulleman & Olivers, 2007). We extended this investigation to shapes that were repeated instead of reflected, to test whether there is a specific convexity advantage for bilateral symmetry. The results supported a convexity advantage for repetitions but not for reflections. Possible explanations for this are discussed. The final series of experiments involved a shape interference task; observers responded to circles or square in the context of irrelevant circles and squares. The findings suggest that interference between the shapes is much stronger when the contours that define the shapes belong to the same surface. In summary, we conclude that convexity and concavity are important aspects of shape analysis and representation, but there is no basic difference in how convexities and concavities are attended to, both in the corner enhancement effect, and in visual-short term memory. However, convexity plays a role in some perceptual tasks for example, when analyzing complex shapes observers may adopt strategies that focus on the convexities.