Both spatial theories of voting and our intuitions lead us to expect that political parties' ideological positions should affect individuals' turnout decisions. Contrary to these expectations, existing research finds that neither feelings of alienation--that no party adequately represents an individual's ideological position--nor indifference--that multiple parties adequately represent an individual's ideological position--have much of an effect on the rate at which individuals turn out to vote. Considering the contradiction between our expectations and existing research, a critical question, then, is why are the effects of alienation and indifference so small? Here, I offer two reasons. The first involves measurement. Invalid measurement of either alienation or indifference would attenuate estimates of their effects on turnout. Since I find that no previous research uses the most valid combination of measures, invalid measurement is one possible explanation for why we find such a small effect. The second reason involves individuals' predispositions for voting. There is evidence that some individuals vote in every election and others abstain in every election. Such predisposed individuals should not be affected by feelings of alienation and indifference because they are predisposed to turn out, or not, at each election. Meanwhile, individuals lacking predispositions should be strongly affected by their feelings of alienation and indifference. As a result, previous researchers, who ignored individuals' predispositions for voting, potentially overestimated the effects of alienation and indifference for those with predispositions and underestimated their effects for those without them. I test these two claims using a combination of experimental and survey data and find that both partially explain the small effects that alienation and indifference are found to have on turnout in previous research. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]