<p>This paper analyzes uses of the term 'transfer' in studies of learning transfer and compares them with the logic of everyday use. We discuss conceptual issues related to the definition of transfer that tend to hinder analysis and comparison of empirical studies. We propose (1) the importance of taking into account empirical and conceptual aspects of the complexity of the tasks involved and (2) avoiding overly restricted definitions of transfer. A theoretical proposal is presented in which tasks involved in transfer of learning are conceived as a set of programmed contingencies of reinforcement, which can be quantified in order to establish a measure of its discriminative complexity.<br /><br /></p>