In two studies, we investigated to what extent typicalities in conjunctive
concepts phrased as relative clauses-such as pets that are also birds-can b
e predicted from simple functions of constituent typicalities and from exte
nsions of such functions. In a first study, analyses of a large aggregated
data set, based on seven different experiments, showed that a calibrated mi
nimum rule model and some extensions of this model accounted for a very lar
ge part of the variance in the conjunction typicalities. The same models ca
n also account for the so-called guppy effect. A psychological explanation
is presented, which states that typicalities in contrast categories, like p
ets that are not birds and birds that are not pets, further improve the pre
diction of conjunction typicalities. This hypothesis is tested in a second
study.