Environmental food-associated stimuli potentiate feeding in non-human animals and humans. However, there has been no investigation of this phenomena in human adults using novel stimuli which are then selectively associated with food through different learning processes. The aims of this thesis were twofold; firstly, to investigate whether Pavlovian cues (those that signal what and when an outcome will occur) and discriminative stimuli (those that signal whether an outcome will occur) which are associated with food will increase subsequent intake. Secondly, to investigate neural activity in response to these stimuli. The first set of studies examined Pavlovian cue-food associations. Study one utilised a new methodology to associate stimuli with specific tastes and demonstrated evidence for cue-potentiated feeding: people ate more in the presence of cues associated with a sweet taste (CS+). This potentiation was greater for foods which were sweet and so constonant with the trained taste. Study two utilised the same methodology but now contrasted sweet likers and sweet-dislikers. However, the cue-potentiation finding failed to replicate. The second set of studies examined cues associated with the chance to obtain food-rewards, interpreted as discriminative stimuli (DS). Study three trained participants to associate stimuli with obtaining food-rewards if the correct response was produced. The findings displayed a suppression of intake in the presence of a stimulus associated with not obtaining rewards compared to a stimulus associated with obtaining chocolate rewards. Study four extended Study three however sated half the participants prior to the intake test. However the previous cue-suppression finding did not replicate. Study five examined how these two different cue-food associations are encoded in the brain using fMRI. Analysis revealed that the stimuli modified activity in neural regions associated with reward, although whereas the DS enhanced striatal activation, the CS+ deactivated the striatum. The evidence for the lack of contingency awareness to affect behaviour throughout the thesis is discussed.

Traditionally, mainstream models of attention have neglected the role of motivationally meaningful stimuli (e.g. threat/reward). These stimuli can cause the rapid and involuntary attraction of attention (attentional capture), and can hence be said to have motivational salience. It is sometimes considered that this capture occurs in a stimulus-driven manner (versus goal-driven). I, however, suggest that attentional capture by motivational salience could be caused by a goal-driven mechanism. To test this we asked three overarching questions: 1) Is detecting motivationally salient stimuli considered important? By using a novel concurrent forced choice task, which isolates the priority of an individual's explicit search goals, we found that individuals believed that it was advantageous to detect and search for motivationally salient stimuli. 2) Can voluntary search goals induce attentional capture? In Chapter 2 we revealed that task-irrelevant threatening stimuli only captured attention, versus neutral distractors, when participants were searching for that category of threatening stimuli. This goal-driven capture effect was robust yet highly specific, affecting only the single specific semantic category, rather than generalising across all related stimuli (Chapter 3). We found an identical pattern of results for reward associated stimuli (alcohol in social drinkers) in Chapter 4, with capture only occurring in the goal-driven condition. The same was true for smoking related images in Chapter 5, and this occurred independently of current nicotine dependence. Additionally, self-selected search goals were capable of inducing attentional capture, not just instructed goals (Chapter 7). 3) How are top-down search goals initially selected? Chapter 6 revealed that search goal priority was positively predicted by stimulus importance and expectancy. This task also revealed a contextual cueing effect on search goal priority, whereby threat was prioritised more in a threatening context (versus safe). On the basis of my findings we propose a novel Importance-Expectancy model of attentional goal selection.

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Research has shown that self-affirmation often leads to more adaptive responses to messages that focus on behaviour-specific, individual threats. However, little is known about the effects of self-affirmation in the context of a multifaceted collective threat, such as climate change. In the current thesis I apply self-affirmation theory to the psychology of climate change. More specifically, I propose that differentially polarized environmental orientations can have an impact on self-affirmation effects. In Chapter 1, I provide a general integration of the self-affirmation literature, the literature on sceptical responses to climate change, and the findings reported in the current thesis. The results from six empirical studies are presented in the following four chapters. In Chapter 2, I present findings that indicated that sceptical responses to climate change information are not always reduced through self-affirmation, but are instead strongly dependent on people's initial levels of rejection of environmental problems. In Chapter 3, I suggest that in the absence of a persuasive threatening message, self-affirmation can serve to validate a person's initial worldviews about environmental issues. In line with this suggestion, results demonstrated that self-affirmation led to more pro-environmental motives among participants with positive ecological worldviews but led to less pro-environmental motives among participants with negative ecological worldviews. In Chapter 4, I examine self-affirmation effects on the acceptance of climate change information. Results showed that self-affirmation promoted perceptions of greater climate change consequences and more self-efficacy among initially sceptical participants. Additionally, self-affirmation reduced pessimism among less sceptical participants. In Chapter 5, I present evidence that showed that self-affirmation resulted in more acceptance of information portraying the UK's contribution to climate change problems among participants with high national identification, while group-affirmation resulted in more information acceptance among participants with low national identification. These effects were only apparent among participants with negative ecological worldviews.

Dopamine and 3',5'-cyclic adenosine monophosphate-regulated neuronal phosphoprotein (DARPP-32) is a critical mediator of neuroplasticity in striatal medium spiny neurons (MSNs). The work presented in this thesis used a global gene knockout (KO) construct to investigate the role of DARPP-32 in reward-based learning and performance. Global deletion of the DARPP-32 gene disturbed performance during the intertemporal (delay) discounting procedure. DARPP-32 KO mice were less sensitive than their wildtype (WT) littermates during long delays to reinforcement. In comparison to WT mice, DARPP-32 KO mice also developed a risk-sensitive pattern of choices during a probability discounting task. Unlike the effects of DARPP-32 deletion on reinforcement along dimensions of time and risk, DARPP-32 knockout did not affect the degree of effort that subjects were willing to invest during food-reinforced progressive ratio testing. DARPP-32 KO mice also failed to exhibit Pavlovian-to-instrumental transfer and this impairment could not be rescued by administering methylphenidate prior to test. Finally, DARPP-32 KO mice were indistinguishable from WT mice during an amphetamine psychomotor sensitisation study. Overall, the data in this thesis suggest DARPP-32 is involved in adaptive reward-based learning and performance.