Frequency estimation and semantic ambiguity do not eliminate ‎conjunction bias, when it ‎occurs: Replication and extension of ‎Mellers, Hertwig, and Kahneman (2001)‎

Mellers, Hertwig, and Kahneman (2001) conducted an adversarial collaboration to try and resolve Hertwig’s contested view that frequency formats eliminate conjunction effects, and that conjunction effects are largely due to semantic ambiguity. We conducted a pre-registered well-powered very close replication ‎(N = 1032), ‎testing two personality profiles (Linda and James) in a four conditions between-subject design comparing unlikely and likely items to "and" and "and are" conjunctions. Linda profile findings were in support of conjunction effect and consistent with Tversky and Kahneman’s (1983) arguments for a representative heuristic. We found no support for semantic ambiguity. Findings for James profile were a likely failed replication, with no conjunction effect. We provided additional tests addressing possible reasons, in line with later literature suggesting conjunction effects may be context-sensitive. We discuss implications for research on conjunction effect, and call for further well-powered pre-registered replications and extensions of classic findings in judgment and decision-making.