Knowing when to say 'I don't know' is fundamental to human judgment. However, AI assistants offer fluent answers to almost any question. In five experiments (N = 3,132; four preregistered, one direct replication), participants answered difficult questions and could always decline to respond. We engineered the questions so that AI advice was wrong, separating AI use from its accuracy. Merely having access to AI nearly eliminated participants' willingness to suspend judgment, whether the advice was actively requested or simply displayed. Consequently, participants answered more questions but were correct about a third as often as when AI was unavailable—yet their confidence nearly doubled. Incentivizing accuracy and penalizing inaccuracy led participants to seek and follow AI advice less, answer more accurately, and suspend judgment more often, though still far less than when AI was unavailable. As AI suggestions grow ubiquitous and unsolicited, they may not only affect answer accuracy; they may even alter the metacognitive threshold at which people decide whether they know enough to answer.
Blogger's Review: This study highlights the negative impact AI assistants can have on decision-making. While the accessibility of information through AI is beneficial, it may weaken individuals' judgment and confidence. Finding a balance between AI use and independent thought is crucial for maintaining cognitive integrity.