- Unlike other forms of priming, semantic priming appears only to occur at short lags. In apparent contrast to this, S. Becker, M. Moscovitch, M. Behrmann, and S. Joordens (1997) described a theory of priming that predicts long-term effects for all forms of relatedness. This prediction is reconciled with previous failures to observe long-term semantic priming on the basis of 2 claims: (a) that previously used pairs share few semantic features and (b) that tasks typically used to study priming are not especially sensitive to semantic influences. The present experiments provide further support for these claims by demonstrating long-term semantic priming in the lexical-decision task when the stimuli and task are modified in a way that increases semantic involvement. However, the findings' suggest that in addition to the mechanism advocated by Becker et al., a second mechanism is necessary to provide a complete account of semantic priming effects.