Re: Please suggest a control for an experiment on ticklishness?

First as to a control...one thing you could do is use the same 40 subjects 
as their own control. The experiment could be done as follows...each 
subject could undergo four different trials: 1) tickled when told they are 
going to be; 2)tickled when not told; 3) just touching them with an open 
hand in the same area where you tickled in that trial after telling them 
as in (1); and 4)just touching an open hand in the same area as you tickled 
wnd not warning them in advance.

All trials should have the same duration of stimulation (or touch),and the 
amount of finger moving (tickling) and pressure of touch should be as 
consistent as possible.

A better way to measure their reaction might be to include varying levels 
of response...like...

0 response= no reaction
1=a slight flinch or movement
2=a more pronounced movement or flinch
3=a move to get away from your hand
4=a move to get away with a slight laugh
5= etc...you get the point and it is up to you to make the definitions for 
each score and how many reactio want to identify.

This method of scoring would make it much easier for you to graph your 
results and to come up with any "statistics" that you might want to do 
like a mean score for each type of stimulus.

By using each subject as their own control...you may get a better result 
then if you used 40 test subjects and another 40 controls...it also allows 
you to have a bigger test group, assuming that subjects for your 
experiment are limited.

Good luck with your experiment...if you need mor help feel free to ask 
more questions and or advice.  Sounds like you are on your way to a career 
in the sciences and I also wish you luck in that endeavor or in whatever 
you decide to pursue. If this is for a science fair...Good Luck in that 
competition.