This study examined the relative contribution of four individual diffe
rence variables to ability to solve analogically related problems in f
our separate problem sequences and for spontaneous and assisted transf
er. Experiment 1 investigated the relationships between problem source
s and targets, the familiarity of problem sources and targets, and the
degree to which subjects spontaneously provided a particular solution
to two target problems. Experiment 2 tested whether combinations of i
ndividual difference variables served as significant predictors of pro
blem solving success in four different source-target problem sequences
. For both spontaneous and assisted transfer, the results indicated th
at under certain circumstances different combinations of the individua
l difference variables were contributing to ability to predict whether
a subject would provide a particular solution to a target problem. Th
e results are discussed in terms of why the individual difference vari
ables enhance prediction for transfer only under certain conditions.