Have you ever tried to tickle yourself?
There are two main theories explaining why this can’t really “work”.
The first and most common (Selden, 2004) is the self-detection model, based on experiments by Blakemore et al. (1998).
According to Selden, our brain recognizes when the stimuli come from ourselves, and block them as they are irrelevant — tickling works as a defense mechanism against external threats.
Blakemore proposed that cerebellum is involved in predicting the specific sensory consequences of movements, providing the signal that is used to cancel the somatosensory response to self-produced tactile stimulation (feed-forward model).
Classic self-computation model, by Leavens & Bard (2016)
The second theory is far less known. Intriguingly, it argues that previous model does not explain why Tickle supresión occurs even when self-tickling is applied at the same time of external tickling.
Ishiyama et al. (2019) proposed the GABAergic Inhibition Suppression Model, which hypothesized that tickle inhibition occurs because of a general suppression of stimuli when self-touch is applied.
GABAergic Inhibition Suppression Model, by Ishiyama (2019)
Which theory tickles you most?