What is the effect of source claims (such as “I saw it” or “Somebody told me”) on the believability of statements, and what mechanisms are responsible for this effect? In this study, we tested the idea that source claims impact statement believability by modulating the extent to which a speaker is perceived to be committed to (and thereby accountable for) the truth of her assertion. Across three experiments, we presented participants with statements associated with different source claims, asked them to judge how much they believed the statements, and how much the speaker was responsible if the statement turned out to be false. We found that (1) statement believability predicted speaker accountability independently of a statement’s perceived prior likelihood or associated source claim; (2) being associated with a claim to first-hand (“I saw that . . .”) or second-hand (“Somebody told me that . . .”) evidence strengthened this association; (3) bare assertions about specific circumstances were commonly interpreted as claims to first-hand evidence; and (4) (everything else being equal) claims to first-hand evidence increased while claims to second-hand evidence decreased both statement believability and speaker accountability. These results support the idea that the believability of a statement is closely related to how committed to its truth the speaker is perceived to be and that source claims modulate the extent of this perceived commitment.

来源声明（例如“我看到了”或“有人告诉我”）对陈述可信度的影响是什么？造成这种影响的机制是什么？在这项研究中，我们通过调节说话者被认为致力于（并因此对其断言的真实性负责）的程度来测试来源主张影响陈述可信度的观点。在三个实验中，我们向参与者提供了与不同来源的说法相关的陈述，要求他们判断自己对这些陈述的相信程度，以及如果该陈述被证明是错误的，说话者要承担多少责任。我们发现（1）陈述可信度预测说话者的责任，独立于陈述的感知先验可能性或相关来源声明； (2) 与第一手证据（“我看到……”）或二手证据（“有人告诉我……”）的主张相关联，强化了这种关联； （3）对具体情况的简单断言通常被解释为对第一手证据的主张； (4)（在其他条件相同的情况下）对第一手证据的主张增加，而对二手证据的主张则降低了陈述的可信度和发言者的责任感。这些结果支持这样一种观点，即声明的可信度与说话者被认为对其真相的承诺程度密切相关，并且消息来源的声明调节了这种感知承诺的程度。