How accuracy instructions change number format and constrain estimate adjustments

This research examines how accuracy motivation shapes numerical estimation by altering the mental representation of the number scale. We demonstrate that accuracy instructions lead individuals to adopt a finer-grained scale, resulting in the use of more precise estimates. This shift appears to be driven by a belief that using a finer-grained scale is necessary for producing accurate estimates, even though greater resolution alone does not guarantee greater accuracy. Across four studies, we show that accuracy instructions consistently increase numerical precision without improving objective estimation accuracy. We also identify an unintended consequence of this shift: adopting a finer-grained scale paradoxically constrains the magnitude of adjustments from initial estimates, even when larger revisions are warranted. These findings reveal a novel unintended consequence of emphasising accuracy, offering new insights into the mechanisms underlying anchoring effects and the broader cognitive processes involved in numerical judgement and decision-making.