In the second treatment, the donors received a small payment.
Indeed, much of what donors receive for their money amounts to good feeling.
In the first treatment, the donors did not receive compensation.
All donors receive photographs of the project taking place in the classroom and a letter from the teacher.
Each donor received a button saying "I gave my tooth to science."
The private donor does not receive the goods or services of the charity.
Donors receive an incentive in form of a token present.
The maximum benefit the donor can receive for a donation of £1,000 is £25.
Of this the donor receives less than $1,000 and may make as little as $250.
Committee members said they were horrified at the public perception that big donors receive special favors in Washington.