This study will identify which areas of the brain mediate the interaction between people
involved in economic decision-making.
Healthy, right-handed native English speakers between 21 and 55 years of age may be eligible
for this study. Candidates are screened with a telephone interview, a questionnaire to
determine handedness, and a neurological examination if one has not been performed within
the last year by an NIH physician.
Participants bargain for money by playing two-person trust games, while undergoing
functional magnetic resonance imaging (fMRI). MRI uses a strong magnetic field and radio
waves to obtain images of body organs and tissues. The MRI scanner is a metal cylinder
surrounded by a strong magnetic field. During the procedure, the subject lies on a stable
that can slide in and out of the scanner, wearing earplugs to muffle loud knocking sounds
that occur with electrical switching of the magnetic fields. Functional MRI involves taking
MRI scans while the subject performs a task-this to learn about how the brain regions are
involved in performing the task. For this test, the subject plays or watches two-person
games involving trust. The game may be played against a stranger or a friend. The winner
receives a cash payoff.
The subject performs one of the following two tasks during MRI scanning:
- Playing the trust games and indicating as quickly as possible by pressing a right or
left button whether he or she wants to stop or continue playing, or
- Observing games that others have played and predicting as quickly as possible by
pressing a right or left button whether the players wanted to stop or continue the
The test takes about 90 minutes. After the scan, participants complete written
questionnaires about their experience in the scanner and their views on issues related to
participating in competitive games.
Objective. The purpose of the protocol is to identify the brain regions mediating the social
cooperation involved in economic decision-making, including whether negative mood and
perceived interpersonal similarity affect behavior or brain regions utilized.
Study Population. Healthy, normal adult volunteers will play and observe two-person
reciprocal trust games during functional neuroimaging against either real people or
computers masquerading as real people.
Design. A between/within-subject, rapid event-related fMRI design will be employed for two
series of experiments. In the first experiment, two persons-each in a separate MRI
scanner-will interact with one another playing two-person reciprocal trust games while their
brains are simultaneously scanned. In the second experiment, a third person will later
observe the played games while in a scanner, trying to predict the decisions of the two
other players in the first experiment. In the third experiment, a sad mood will be induced
in half of the participants to examine if it affects levels of cooperative behavior and
patterns of brain activation in the two types of trust games described above.
Four additional series of experiments will employ between/within subject designs in which
subjects are scanned alone, but under the deception that they are playing simultaneously
with another subject.
Outcome Measures. The data collected will consist of behavioral measures of cognitive
performance, self- and other-mental representation, trusting and trustworthy behavior,
corresponding fMRI images, personality scales, ratings of relationship and status, and types
of strategy used. The results gained from this protocol will be of value in identifying a
set of neural regions mediating dynamic social interaction between people engaged in
- INCLUSION CRITERIA:
In all the studies, subjects will consist of healthy, native English-speaking,
right-handed volunteers, as measured by the Edinburgh Handedness Inventory (Oldfield,
1971). Subjects will range in age from 21 to 55 years old and they will be included
regardless of race.
Non-native English speakers and non-right handers will be excluded as mentioned above, as
will non-neurologically normal volunteers. Subjects younger than 21 and older than 55 will
be excluded. A urine pregnancy test will be employed with all women of childbearing age.
The results must be negative in order to proceed with the MRI.
Participants with any of the following: aneurysm clip; implanted neural stimulator;
implanted cardiac pacemaker or auto-defibrillator; cochlear implant; ocular foreign body,
e.g. metal shavings; permanent eyeliner; insulin pump; or irremovable body piercing will
be excluded from the study due to the possible dangerous effects of the magnet upon metal
objects in the body. Participants taking central nervous system active medications will be