Electrophysiological correlates of adjustment process in anchoring effects

Anchoring is a judgmental bias that final judgments are assimilated toward the starting point of the judge's deliberations. The anchoring-and-adjustment heuristic holds that anchoring bias is caused by insufficient adjustment. With the manipulation of some subjective factors, previous research found that anchoring is an effortful process. However, there is little evidence supporting that the effortful process is an adjustment process. In the present work, number accuracy was introduced as an objective factor which involves in an adjustment process. An event-related brain potential (ERP) experiment on young normal subjects examined the impact of number accuracy on anchoring processes responding to anchors which were generated by subjects themselves. A dot-image paradigm was firstly employed to explore anchoring effects. Behavioral results found less accurate anchors which determined a coarser mental scale diminished the anchoring biases responding to self-generated anchors. A positive deflection at 250-800 ms after target onset can be taken as a direct electrophysiological evidence of the adjustment process, whose amplitude was more positive on more accurate anchors condition. The present results further support that people adjust upwards or downwards on a mental scale from the self-generated anchor, which is consistent with the adjustment heuristics. (C) 2008 Published by Elsevier Ireland Ltd.