Experimentation is a powerful methodology that enables scientists to
empirically establish causal claims. Even in social sciences
where
traditionally observational studies were dominant, experiments
are
becoming increasingly common. However, one general and
important
criticism of experimental methodology is that experiments merely
provide a black-box view of causality -- although experiments
can
identify an average causal effect, they cannot explain how such
an
effect comes about. If true, this represents a serious
limitation
of experimentation, especially for social science research whose
main goal is to identify causal mechanisms. In this paper, we
first
establish that two existing approaches commonly employed by
social
scientists to address this critique suffer from serious
methodological problems. To overcome this limitation, we
consider
alternative experimental designs that can be used to help
identify
causal mechanisms. Finally, we discuss the situations in which
these experimental designs are applicable and illustrate their
use
by applying them to a decision neuroscience experiment.
(Last Revised September, 2009)
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