The effects of mental contamination on the hindsight bias: Source confusion determines success in disregarding knowledge

Abstract

We present data from eight experiments in which we explored the effects of source confusion on the hindsight bias; participants' success in disregarding information when they were instructed to do so was affected by participants' level of source confusion. In Experiment 1 we demonstrated participants' failure to disregard Revolutionary War information they recently learned while reading an essay; this failure to discount was not affected by participants' essay reading times (Experiment 1a). In Experiment 2 participants successfully discounted obscure War of 1812 information; this discounted information remained available in memory (Experiment 2a). In a direct test of source confusion (Experiment 3) we showed that participants discriminated between presented and not-presented War of 1812 information better than they discriminated presented and not-presented Revolutionary War information. In Experiments 4 and 4a we tested and rejected a motivational explanation for our findings, namely that subjects voluntarily withheld information when asked to disregard it. We tested a debiasing technique in Experiment 5 and found it was successful in helping participants discount familiar information. Results throughout are discussed as being attributable to source confusion. © 2008 John Wiley & Sons, Ltd.