Individual differences in behavior are understood generally as arising from an interaction between genes and environment, omitting a crucial component. The literature on animal and human learning suggests the need to posit principles of learning to explain our differences. One of the challenges for the advancement of the field has been to establish how general principles of learning can explain the almost infinite variation in behavior. We present a case that: (a) individual differences in behavior emerge, in part, from principles of learning; (b) associations provide a descriptive mechanism for understanding the contribution of experience to behavior; and (c) learning theories explain dissociable aspects of behavior. We use 4 examples from the field of learning to illustrate the importance of involving psychology, and associative theory in particular, in the analysis of individual differences, these are (a) fear learning; (b) behavior directed to cues for outcomes (i.e., sign- and goal- tracking); (c) stimulus learning related to attention; and (d) human causal learning.