Why do we laugh when we're tickled | Greg Foot | Ask Head Squeeze

To kick off #AskHeadSqueeze Thursdays, Greg Foot is answering a great question from YouTuber James the Weirdo who asked us to 'Explain why tickling and pressure points do the funny things that they do'.

Greg answers that and many more questions in this video!

00:29 What is a tickle?

When you're touched, the nerve endings under your epidermis (top layer of skin) send electrical signals to the brain to be interpreted. When we're tickled the somatosensory cortex picks up the signals to do with pressure, but the anterior cingulated cortex also analyses the signals. This part of the brain governs pleasurable feelings.

More on skin and our nervous system here: http://www.cumc.columbia.edu/dept/derm/SkinTouch_Issue_3.pdf

01:36 Why can't we tickle ourselves?

The cerebellum at the back of the brain tells you that you're about to self-tickle so the brain doesn't waste up precious time interpreting the signals from the tickle!

Greg's FOOT NOTE 1:
Bays PM, Flanagan JR, Wolpert DM.
'Attenuation of self-generated tactile sensations is predictive, not postdictive'
Public Library of Science: Biology (2006) 4(2): e28
http://psyc.queensu.ca/~flanagan/papers/BayFlaWol_PLoSB_06.pdf

02:04 Why do people laugh when they're tickled?

Evolutionary biologists and neuroscientists believe that we laugh when we're tickled because the part of the brain that tells us to laugh when we experience a light touch, is also the same part that tells us to expect a painful sensation. It's called the hypothalamus. Laughing when we're tickled in our vulnerable spots (under the arms, near the throat and under our feet) could be a defensive mechanism. Research suggests that we've evolved to send this signal out to show our submission to an aggressor -- basically to dispel a tense situation and prevent us from getting hurt.

FOOT NOTE 2:
Wattendorf E, Westermann B, Fiedler K, Kaza E, Lotze M, Celio M.
'Exploration of the Neural Correlates of Ticklish Laughter by Functional Magnetic
Resonance Imaging'
Cereb. Cortex (2012) doi:10.1093/cercor/bhs094
http://www.ncbi.nlm.nih.gov/pubmed/22508768

03:47 BONUS FACT! Gorillas laugh like us when they're tickled. This could mean that we've been laughing when we're tickled for 30-60 million years! Bonkers!

FOOTNOTE 3:
Ross MD, Owren MJ, Zimmermann E.
'Reconstructing the Evolution of Laughter in Great Apes and Humans
Current Biology (2009): Vol. 19, Issue 13, pp. 1106-1111'
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2889984/

04:18 BONUS BONUS FACT! Rats laugh when they're tickled too, but they giggle at 50kHz which is out of our audio range.

FOOT NOTE 4:
Panksepp J, BurgdorfJ.
'50-kHz chirping (laughter?) in response to conditioned and unconditioned tickle-induced reward in rats: effects of social housing and genetic variables.'
Behavioural Brain Research (2000) 115(1): 25-38.
http://www.sciencedirect.com/science/article/pii/S0166432800002382

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Want more about what sets off our funny bones? Here's James May on 'Why do we laugh?'

http://www.youtube.com/watch?v=cZxUA0KDoVg

And there's even a formula to ensure your jokes get a laugh!:

http://www.youtube.com/watch?v=jKpz6ly5BtY&list=PLMrtJn-MOYmetIk82cAI7T9Efd3x92qcu

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