Psychologist Paul Rozin's research into disgust illustrates an interesting phenomenon regarding how negative stimuli can overpower positive ones. He found that the presence of a single cockroach can diminish the desirability of a bowl of cherries entirely, demonstrating how one unpleasant element can spoil a fundamentally good situation. In contrast, the reverse is not true; having a cherry in a bowl of cockroaches does not improve their appeal. This highlights the strength of negative associations on human perception.

This observation from Rozin emphasizes the psychological principle that negative experiences often have a greater impact than positive ones. As presented by Daniel Kahneman in his book "Thinking, Fast and Slow," this idea sheds light on the cognitive biases humans face. It suggests that our minds are more attuned to avoid disgust and negative outcomes than to seek out pleasure, indicating that the human psyche is more sensitive to threats than to rewards.