Thurgood Marshall emphasized the importance of public opinion as a direct indicator of the "evolving standards of decency" necessary to assess the constitutionality of capital punishment under the Eighth Amendment. Justice Marshall's assertions regarding the effects of information on public support for the death penalty opened a line of social science inquiry and spurned a flurry of empirical investigations of what are referred to as the "Marshall hypotheses". These hypotheses are: support for capital punishment is inversely associated with knowledge about it, exposure to information about capital punishment produces sentiments in opposition to capital punishment, but exposure to information about capital punishment will have no impact on those who support it for retributive reasons. To date, there are almost 30 published studies that have tested one or more of these hypotheses. The first of the Marshall hypotheses argues that American citizens tend to support capital punishment because the public is uninformed about it.