Different involuntary mechanisms underlie priming and LOP effects in stem completion tests

The role of intentional retrieval, involuntary conscious memory, and lexical processing in priming and levels‐of‐processing (LOP) effects in stem completion tests was investigated in three experiments. First, Experiment 1 provided strong evidence against the intentional retrieval hypothesis for the implicit LOP effects. LOP effects in the explicit test were dependent on intertrial interval at test, whereas LOP effects in the implicit test were not. Second, support was provided for the involuntary conscious memory hypothesis. Implicit memory (priming) was associated with awareness in all three experiments and the implicit LOP effect was associated with awareness in two of the three experiments. Third, it was concluded that lexical processing per se played a limited role in both priming and implicit LOP effects. Although priming was sensitive to normative rates of production in Experiment 1 and the number of solutions in all three experiments, it was insensitive to frequency manipulations. The LOP effect was insensitive to number of solutions, normative rates of production, and frequency manipulations. In addition, LOP and priming effects were uncorrelated in the implicit memory tests. It was concluded that production processes (e.g., Gabrieli et al., 1999), rather than lexical processes, played a crucial role in stem completion priming. In contrast, the LOP effect was attributed to the involuntary interaction of episodic and perceptual memory.