Rats know how to laugh.

The claim that rats know how to laugh is supported by evidence showing that rats emit ultrasonic sounds when tickled, indicating pleasure and joy similar to laughter in humans. Multiple studies, including those cited from medium-reliability sources, suggest that these sounds are an indication of positive emotions. However, while the evidence suggests rats exhibit behaviors akin to laughter, the interpretation of these sounds as 'laughter' is more an anthropomorphic description rather than a technical one. Overall, there is a consensus that rats display positive emotional responses that can be likened to laughter.