Judging a book by its cover (and its background): effects of the metaphor intelligence is brightness on ratings of book images:

Visual metaphors have been the focus of experimental and corpus studies aiming to determine whether metaphors are conceptual or purely linguistic. However, in visual metaphor research, experimental and corpus approaches have each been directed at a distinct set of visual metaphors. Psychological experiments have focused on primary metaphors, whereas corpus studies have concentrated on non-primary metaphors. The current study suggests that when non-primary metaphors are examined experimentally, cognitive effects appear only when the metaphor is contextually relevant. intelligence is brightness, for example, is not relevant when the potential source of intelligence is inaccessible. In this study, images of open books with bright backgrounds are rated as more likely to represent works of genius than open books with darker backgrounds. When books are closed, their ‘genius’ is inaccessible and intelligence is brightness has no effect.