Evidence for the contribution of a threshold retrieval process to semantic memory

It is widely held that episodic retrieval can recruit two processes, a threshold context retrieval process (recollection) and a continuous signal strength process (familiarity). Conversely, and in spite of its importance for everyday memory, the processes recruited during semantic retrieval are less well specified. We developed a semantic task analogous to single-item episodic recognition to interrogate semantic recognition receiver operating characteristics (ROCs) for a marker of a threshold retrieval process. We then fit observed ROC points to three signal detection models: two models typically used in episodic recognition (unequal variance and dual process signal detection models) and a novel dual process recollect-to-reject (DP-RR) signal detection model that allows a threshold recollection process to aid both target identification and lure rejection. Given the nature of most semantic questions used here, we anticipated the DP-RR model would best fit the data obtained from our semantic task. In Experiment 1 (506 participants), we found evidence for a threshold retrieval process in semantic memory, with overall best fits to the DP-RR model. In Experiment 2 (316 participants), we found within-subjects estimates of episodic and semantic threshold retrieval to be uncorrelated, suggesting the relationship between the analogous memory processes is not straightforward. Our findings add weight to the proposal that semantic and episodic memory are served by similar dual process retrieval systems, though the relationship between the two threshold processes needs to be more fully elucidated.