<human>: I am researcher at a R&D Center in a european university. Tomorrow I am receiving the visit of students of a nearby college to talk about what is our job as researchers and what we do in our Center. I have about an hour to talk and also thought of talking a little about the scientific method, blind experiments and placebo effect. 

I think it would be fun and more easy for them to grasp the concept to have a real experiment conducted with the students, so I would enjoy some ideas for a double-blind placebo controlled experiment that can be conducted in under 30 minutes. 
I had prepared something related to short term memory and numbers, to test if it can be improved with the association of images, but I would like to come up with something more clear.

In my idea, I will separete students in three groups, will give each group a separate set of instructions to read, and will show them two strings of 9 digit numbers. After one minute will ask them to write the numbers down:

Group 1 - control group. Instructions are blank.

Group 2 - placebo group. Instructions are to read the numbers to themselves and repeat them until the time is passed. (Hypothesis is that this is what a person without any other strategy does anyway)

Group 3 - experimental group. Instructions are to think of the numbers as images that I will provide them (1 as a walking stick, 2 as a swan, and so on), and construct a visual string of images with the digits of the numbers)

As you can see it is not a very good idea, it has several shortcomings such as placebo and control groups being not really well constructed.

Any better ideas??????

Can you give me the gist of the text in a nutshell?
<bot>: I would like to put some college students through a real double blind placebo controlled experiment. I will talk to them for one hour tomorrow in a visit to my university. Any ideas??