Though people often believe their visual experiences reflect the objective state of the surrounding world, a wealth of recent evidence suggests that perceptions are systematically biased. We draw from contemporary research and supplement with real world anecdotes to suggest that two aspects of perception are subject to influence by states internal to perceivers themselves. We focus on the biases that arise from two difficult tasks faced by the visual system. First, visual information is often unclear and ambiguous; yet visual input must be categorized quickly and efficiently. Second, people can focus on only a subset of perceptual information at once, and as a result visual attention is necessarily directed at a subset of the surrounding world. We document ways in which expectations, desires, and fears help to resolve perceptual ambiguity and direct attention. Finally, we discuss the functional nature of visual biases and note potential consequences in important domains.