Substantial evidence indicates that depression focuses attention on the problems that caused the episode, so much that it interferes with the ability to focus on other things. We hypothesized that depression evolved as a response to important, complex problems that could only be solved, if they could be solved at all, with an attentional state that was highly focused for sustained periods. Under this hypothesis, depression promotes analysis and problem-solving by focusing attention on the problem and reducing distractibility. This predicts that attentionally demanding problems will elicit depressed affect in subjects. We also propose two control-process mechanisms by which depression could focus attention and reduce distractibility. Under these mechanisms, depression exerts a force on attention like that of a spring when it is pulled or like a magnet on a steel ball. These mechanisms make different predictions about how depressed people respond emotionally to a task that pulls attention away from their problems. We tested these predictions in a sample of 115 undergraduate students. Consistent with our main prediction, initially non-depressed subjects experienced an increase in their depressed affect when exposed to an attentionally demanding task. Moreover, the overall pattern of results supported the magnet metaphor.