"For people with depression the world really does look dull. That's because their ability to perceive contrast is impaired." A new experiment could help diagnose clinical depression. Participants in a study that examined clinically depressed peoples ability to discern color contrast relative to clinically healthy people were less able to discern contrast if they were clinically depressed. The experiment placed subjects in front of screens that moved from black to white and recorded the frequency of nerve responses to the color changes. Those diagnosed with clinical depression recorded fewer responses thus indicating they were less able to perceive subtle color contrasts.