Here's an exercise about personality that can be done in class or online.
In Class Approach
This works particularly well at the start of an introductory psychology course, or any course which covers personality as part of the syllabus. When you get to the topic of personality, tell students there is a questionnaire that can accurately describe aspects of their personality.
The exercise continues by getting your students to rate on a scale of zero (poor) to five (perfect) the extent to which your description reveals basic characteristics of their personality. I would suggest having students write down their responses (1-5) on a piece of paper. After the last questionnaire you can collect the results. Then write the numbers 1 to 5 on the board and then place a check mark next to a number as you or a student read off the scores students gave to themselves. Or this can simply be done by a show of hands. You can expect students to rate at the high end of the scale on every question and it's important to tell the class that in most cases, this type of personality sketch consistently receives ratings of 4 or 5 from everyone who takes it.
We have created an online version of this demonstration. Click here to see this version. Also, if you'd like to use this online version for your class, feel free to give this link to your students. You can also contact the higher ed community manager if you'd like to get a copy of these files for use with your own class.
The online version explains the demonstration's real purpose, but if you're doing this in class, this is the point at which you tell the class that their responses to these questions was simply a demonstration of how people can be misled by a general personality description, thus highlighting the human susceptibility to interpret broadly applicable statements as uniquely meaningful; a psychological process often to referred to as the Barnum Effect named after the celebrated American showman P.T Barnum's famous remark that "we've got something for everyone"; and also known as the Forer Effect in recognition of Bertram R. Forer's classic research paper into the subject which was published in 1949 under the title "The Fallacy of Personal Validation: A Classroom Demonstration of Gullibility."
"A naive person who receives superficial diagnostic information, especially when the social situation is prestige-laden, tends to accept such information. He [or she] is impressed by the obvious truths and may be oblivious to the discrepancies" (Forer, 1949).
If you want to take the exercise up a level, suggest that this is why so many people believe in horoscopes.
I highly recommend this exercise, not least because it allows you to press home the point that studying psychology promotes critical thinking, which in turn, according to Paul Valéry helps to give us "a completely different idea of the things we know best".