The influence of relatedness proportion on the joint relationship among word frequency, stimulus quality, and semantic priming in the lexical decision task

In the lexical decision task, the additive effects of stimulus quality and word frequency have been used to infer the presence of independent processing stages in visual word recognition. Importantly, this pattern can be moderated by semantic priming, suggesting the presence of a retrospective prime retrieval mechanism that is selectively engaged based on task context (i.e., utility of the primes). We examine the sensitivity of this mechanism in two lexical decision experiments that manipulate stimulus quality, word frequency, and semantic priming. Critically, we studied these joint effects when the proportion of related primes was set at .50 or .25. Results indicated that with a .50 relatedness proportion, a three-way interaction was obtained such that additivity between frequency and stimulus quality was found following related semantic primes, but an overadditive pattern was exhibited following unrelated primes. When the relatedness proportion was reduced to .25, this interaction was eliminated. Furthermore, relatedness proportion affected the magnitude of the stimulus quality by priming interaction but not the frequency by priming interaction. These results are interpreted within the context of a flexible lexical processer that adaptively engages processes in response to task context.

Dissociating N400 Effects of Prediction from Association in Single-word Contexts

When a word is preceded by a supportive context such as a semantically associated word or a strongly constraining sentence frame, the N400 component of the ERP is reduced in amplitude. An ongoing debate is the degree to which this reduction reflects a passive spread of activation across long-term semantic memory representations as opposed to specific predictions about upcoming input. We addressed this question by embedding semantically associated prime–target pairs within an experimental context that encouraged prediction to a greater or lesser degree. The proportion of related items was used to manipulate the predictive validity of the prime for the target while holding semantic association constant. A semantic category probe detection task was used to encourage semantic processing and to preclude the need for a motor response on the trials of interest. A larger N400 reduction to associated targets was observed in the high than the low relatedness proportion condition, consistent with the hypothesis that predictions about upcoming stimuli make a substantial contribution to the N400 effect. We also observed an earlier priming effect (205–240 msec) in the high-proportion condition, which may reflect facilitation because of form-based prediction. In summary, the results suggest that predictability modulates N400 amplitude to a greater degree than the semantic content of the context.

Face (and Nose) Priming for Book

There are two general classes of models of semantic structure that support semantic priming effects. Feature-overlap models of semantic priming assume that shared features between primes and targets are critical (e.g., cat-DOG). Associative accounts assume that contextual co-occurrence is critical and that the system is organized along associations independent of featural overlap (e.g., leash-DOG). If unrelated concepts can become related as a result of contextual co-occurrence, this would be more supportive of associative accounts and provide insight into the nature of the network underlying “semantic” priming effects. Naturally co-occurring recent associations (e.g., face-BOOK) were tested under conditions that minimize strategic influences (i.e., short stimulus onset asynchrony and low relatedness proportion) in a semantic priming paradigm. Priming for new associations did not differ from the priming found for pre-existing relations (e.g., library-BOOK). Mediated priming (e.g., nose-BOOK) was also found. These results suggest that contextual associations can result in the reorganization of the network that subserves “semantic” priming effects.