Monetary Reward Damages Intrinsic Drive

Topic: Relationship between motivation drives.
Researchers: Edward L. Deci, Professor of Psychology and Social Science, University of Rochester, US.
Published At: Journal of Personality and Social Psychology.
Year: 1969
Formal Reference: Edward L. Deci, “Effects of Externally Mediated Rewards on Intrinsic Motivation”, Journal of Personality and Social Psychology 18 (1971), 105-115.
Main Conclusion: External reward (money) can deliver a short-term boost of motivation, but when money is used as an external reward, the subject loses intrinsic interest for the activity.

Description of Experiment
a. University students (male and female) divided into two groups: experimental Group A. and control Group B.
b. Each student went through 3 one-hour sessions held on consecutive days.
c. The experiment used the Soma Puzzle, which looks like this (see YouTube for various demonstrations of this game):

d. Session description: student enters a room, sit by a table, on top of which placed the seven Soma puzzle pieces, drawings of 3 puzzle configurations, and copies of Time, The New Yorker, and Playboy. The researcher sat on the opposite of the table.
e. First session: both groups’ students requested to assemble the Soma pieces to replicate the configurations in front of them.
f. Second session: same task, new drawings, while Group A. students are offered $1 (equal to $6 today) for every configuration they successfully reproduce (Group B. offered no pay).
g. Third session: same as the first session, using new drawings (Group A. participants were told there was only enough money to pay them for one day).
h. To conclude, the 3 sessions looks like this:

First Session (Day 1) Second Session (Day 2) Third Session (Day 3)
Group A. No Pay $1 Pay No Pay
Group B. No Pay No Pay No Pay

i. On each session, after the participant assembled the pieces to match two of the three configurations, the researcher left the room (making excuse of feeding results to the computer and bringing a fourth drawing) and said: “I shall be gone only a few minutes, you may do whatever you like while I’m gone”. He then watched the participants, for eight minutes, from another room through a one-way window.
j. First session findings: participants played with the Soma puzzle for an average of 3.5-4.0 minutes. No real difference between Group A. and group B.
k. Second session findings: Group A. played with the Soma puzzle during the free-choice-time for 5 minutes on average, while Group B. participants behaved no different than the first session. (3.5-4.0 minutes on average).
l. Third session findings: Group A. played with the puzzle for an average time of 2.5-3.0 minutes while group B. played with the puzzle as before, or a bit more time.

External reward (money) enhances short-term interest.
External reward (money) may damage intrinsic motivation to do a certain activity.
Non-biological intrinsic drive (the 3rd drive) might be damaged in the presence of external reward (the 2nd drive).