Assessing the differential effect of poll exposure on voting behaviour

近年来，在未能预测2015年和2017年的选举结果以及英国退欧公投结果后，政治民调受到了越来越多的关注。鉴于此而进行的调查最终在最近上议院特别委员会的一份报告中达到高潮，该报告呼吁民调行业“整顿好自己的内部秩序”，但值得注意的是，拒绝了在任何时间内禁止民调发布的案件。这在一定程度上可以用最近的一项发现来解释，即这类失败在很大程度上并没有偏离历史上普遍存在的不准确的标准，但它也被框定为民意调查对公众舆论的影响。也就是说，民调机构欢迎专责委员会的结论，理由是任何基于不准确预测可能不公平地影响投票的潜在投票中断，都无法解释这样一个事实，即在没有民调的情况下，人们仍然可能受到他们(甚至更容易出错)对结果的预期的影响。然而，考虑到大量且不断增长的研究假设地证明了潮流效应的存在，这种观点很奇怪，根据这种效应，选民接触民意调查会给领先的候选人带来进一步的优势。因此，考虑到这篇文献中提出的证据，民调似乎会以一种许多人可能认为不民主的方式影响选举结果。然而，我认为，这一断言因这部作品中在概念上的不足而受到威胁。不仅不同的研究人员对潮流效应的定义松散而不同，而且很少有人试图确定这种效应产生的因果机制。这种随波逐流效应可能只存在于某些个人中，取决于某些特征或情况，例如与身份、党派、知识、情感、政治参与或效力有关。甚至可能是，当控制正确的替代解释时，这种影响根本不存在。此外，尽管对这一效应的观察研究一直在努力解决内部有效性问题，但在缺乏对潮流效应的明确理论表达的情况下，通过提供理论上合理的处理来最大化实验现实主义的关键要求在实验研究中被忽视了。因此，我的论文对这种情况进行了评估，旨在通过明确定义正在发挥作用的概念，在全面阅读现有学术的基础上假设这些概念可能通过的几种机制，并通过联合分析来检验这些机制，从而重新定位文献。这种方法使我能够通过提供多层次、细致入微和现实的处理方法与理论密切接触，产生可应用调解和缓和分析的输出，以清楚地确定数据中证实了哪些机制，并直接控制替代解释。除了重新确立我们如何更广泛地思考潮流效应和民调效应的概念贡献外，我还将就如何产生此类效应(如果存在的话)提供新的经验主义见解，并进一步理解如何将联合分析运用于政治行为研究。

Political polling has come under increased scrutiny in recent years following notable failures to predict the 2015 and 2017 election outcomes, as well as the result of the Brexit referendum. Inquiries undertaken in light of this culminated in a recent House of Lords Select Committee report calling for the polling industry to 'get its house in order', but, notably, rejecting the case forbanning poll publication for any time period. This could partly be explained by the recent finding that such failures do not majorly diverge from the norm of historically endemic inaccuracy, but it has also been framed in terms of the influence of polls on public opinion. That is, pollsters welcomed the Select Committee's conclusions on the grounds that any potential polling blackout, founded on the idea that inaccurate forecasts could unfairly sway the vote, would fail to account for the fact that, in the absence of polls, people could still be influenced by their (even more prone to error) expectations of the outcome. This notion is curious, however, given the large and growing body of research putatively demonstrating the existence of a bandwagon effect, according to which voter exposure to opinion polls gives further advantage to the leading candidate. It would therefore seem, given the evidence presented in this literature, that polls affect electoral outcomes in a way many might deem undemocratic. I argue, however, that such an assertion is jeopardised by conceptual inadequacies within this body of work. Not only is the bandwagon effect loosely and differently defined by different researchers, but also very few attempts have been made at identifying the causal mechanisms through which this effect is had. It may be that the bandwagon effect only exists among certain individuals, contingent on certain characteristics or circumstances, related for example to identity, partisanship, knowledge, emotions, political engagement or efficacy. It may even be that the effect does not exist at all when controlling for the correct alternative explanations. Moreover, while observational studies of this effect have struggled to deal with issues of internal validity, in the absence of clear theoretical expressions of the bandwagon effect, the crucial requirement of maximising experimental realism - by providing theoretically sound treatments - has been overlooked in experimental studies. My thesis, therefore, takes stock of this situation and aims to reorient the literature by clearly defining the concepts at play, hypothesising several mechanisms through which these may operate based on a comprehensive reading of existing scholarship, and testing these through conjoint analysis. This method allows me to engage closely with theory by offering multi-layered, nuanced and realistic treatments, produces an output to which mediation and moderation analyses can be applied to identify clearly which mechanisms are borne out in the data, and directly controls for alternative explanations. In addition to the conceptual contribution of reestablishing how we can think about bandwagon effects and poll effects more broadly, I will thus offer novel empirical insights into how any such effect might be had, if it exists at all, and further our understanding of how conjoint analysis can be deployed in studies of political behaviour.