The results of any one study showing that individuals with the CC genotype score higher on a novelty-seeking questionnaire than individuals with the CT or TT genotype might be interesting, but unconvincing. Questions might remain about the population from which the subjects were chosen, the number of subjects used, the laboratory methods used in determining genotypes, the conditions under which the questionnaire was administered, and a whole range of unconscious, inadvertent, or otherwise hidden biases that the researchers may have had. But it is powerful when the results of all 11 studies that tested this hypothesis are reported and most of the studies seem to show similar results. This means that you can be more certain about the conclusions drawn in any one of the studies. It's important that all of the studies conducted on this hypothesis were collected and analyzed, rather than the meta-study simply selecting studies that supported or rejected the hypothesis. We can have more confidence in concluding that an individual's genotype for this gene influences novelty-seeking behavior. (In fact, though, without information about how well a peron's score on this questionnaire predicts actual behavior, it might be safer to simply conclude that individual's genotype influences his or her score on a novelty-seeking questionnaire. This conclusion gives rise to numerous new hypotheses that could be tested.)