The generation of predictions shapes our experience of the world around us. By making inferences about what is likely to happen within a given scenario, we can conserve cognitive resources and enhance our prospects of survival. Predictive coding accounts of perception indicate that this is achieved by minimally processing information that is consistent with our expectations, and prioritising the processing of unexpected or meaningful information. Predictions are also beneficial in situations where accurate perception is difficult, and clues like contextual information allow expectations to 'fill in the blanks' when sensory information is noisy or ambiguous. This comes at a cost, however, and a reliance upon expectations can lead to perceptual biases, and in certain cases misperceptions.According to Assimilation Contrast Theory (ACT) and the Affective Expectation Model (AEM), when we attempt to judge affectively ambiguous stimuli, our judgements are biased by expectations in a similar manner. If stimuli are within an acceptable range of an existing expectation, minor discrepancies will be ignored and judgements of those stimuli will fall in line with expectations (assimilation). Alternatively, if the affective discrepancy between expectation and stimulus is so large that it is acknowledged, the extent of that discrepancy will be exaggerated instead (contrast). This thesis aimed to investigate the boundaries and time-course of these effects.A series of behavioural experiments were conducted to investigate: (i) whether predictive cues promoted a state of affective readiness, where judgements across a range of stimuli were biased based upon the assumption that they were broadly part of a positive or negative category (chapters 3 and 4); (ii) whether affective biases (assimilation effects) persisted over time (chapters 5 and 6); and (iii) whether the boundaries of affective and perceptual assimilation effects remained consistent over time (chapter 6 and 7). Psychophysical measures of affective bias indicated that predictive cues influenced participants to judge the same stimuli differently, according to whether they expected those stimuli to be positive or negative. Furthermore, after expectations were learned, judgements of the same stimuli continued to be biased toward expectations after a period of one week. When stimuli from affectively or perceptually distinct categories were manipulated slowly over time, to the point where they became identical, judgements of those stimuli continued to be influenced by the expectation that they should remain distinct. These findings indicate that the boundaries of perceptual and affective assimilation effects may not be static, and if deviations from expectation are small enough to go generally unnoticed, people may update their internal representations of items over time, and the boundaries of acceptance which surround those representations.