The so-called Alan Author Effect is a surprising phenomenon in Bayesian Confirmation Theory. It occurs when a piece of evidence e confirms the conjunction of two hypotheses h1∧h2 but at the same time disconfirms each hypothesis h1 and h2 individually. In this paper, I present a new and prima facie stronger version of this effect where additionally, the evidence e confirms the conjunction of the negated hypotheses ¬h1∧¬h2. I say ‘prima facie’ because it can be shown that this seemingly stronger (...) effect and the original effect are actually coextensional. I use this insight to formulate a new sufficient (and also necessary) condition for the two equivalent effects. I also examine how likely the two effects are to occur with the help of Monte Carlo simulation methods. (shrink)

Crupi et al. (Think Reason 14:182–199, 2008) have recently advocated and partially worked out an account of the conjunction fallacy phenomenon based on the Bayesian notion of confirmation. In response, Schupbach (2009) presented a critical discussion as following from some novel experimental results. After providing a brief restatement and clarification of the meaning and scope of our original proposal, we will outline Schupbach’s results and discuss his interpretation thereof arguing that they do not actually undermine our point of view if (...) properly construed. Finally, we will foster such a claim by means of some novel data. (shrink)

It is argued that the conjunction effect has a disjunctive analog of strong interest for the realism–antirealism debate. It is possible that a proper theory is more confirmed than its (more probable) observational sub-theory and hence than the latter’s disjunctive equivalent, i.e., the disjunction of all proper theories that are empirically equivalent to the given one. This is illustrated by a toy model.