Just say 'I don't know': Understanding information stagnation during a highly ambiguous visual search task

Visual search experiments typically involve participants searching simple displays with two potential response options: 'present' or 'absent'. Here we examined search behavior and decision-making when participants were tasked with searching ambiguous displays whilst also being given a third response option: 'I don't know'. Participants searched for a simple target (the letter 'o') amongst other letters in the displays. We made the target difficult to detect by increasing the degree to which letters overlapped in the displays. The results showed that as overlap increased, participants were more likely to respond 'I don't know', as expected. RT analyses demonstrated that 'I don't know' responses occurred at a later time than 'present' responses (but before 'absent' responses) when the overlap was low. By contrast, when the overlap was high, 'I don't know' responses occurred very rapidly. We discuss the implications of our findings for current models and theories in terms of what we refer to as 'information stagnation' during visual search.