Studies have been carried out on rats. These studies have confirmed that some rats being tickled will laugh, and that some of the rats enjoy being tickled. The laugh can’t be heard by human ears as it is of such a high frequency, it is ultrasonic. However, the laughing has been recorded through the scientific equipment used by the scientists when carrying out the study, so you can listen to a rat’s laugh through a link.
The study showed that rats will only laugh if they are already in a good mood, and if the rats aren’t in a good mood, they will not laugh when they are being tickled. For example, if a rat is feeling anxious when it is being tickled, it won’t show any signs of enjoying this and will not laugh. The scientists have done research and found out that the part of the brain which is called the somatosensory cortex is related to the good mood and the laughter.