Repeating an experiment to see whether the results are the same is our final method of control. Replication allows us to weed out spurious findings. We rarely see direct replication of studies in the published literature because there is a great deal of pressure to make new contributions to a field. Instead, researchers often try to build or improve upon a particular aspect of the design, by eliminating potential confounds. Such an approach constitutes a partial replication and extension of previous work.