The negation-induced forgetting effect remains even after reducing associative interference

Recent research has provided evidence that negation processing recruits the neural network of response inhibition (de Vega et al., 2016). Furthermore, inhibition mechanisms also play a role in human memory. In two experiments, we aimed to assess how producing a negation in a verification task may impact long-term memory. Experiment 1 used the same memory paradigm as Mayo et al. (2014), consisting of several phases: first, reading a story describing the activity of a protagonist, immediately followed by a "yes-no" verification task, then a distractive task, and finally an incidental free recall test. Consistent with the previous results, negated sentences were recalled worse than affirmed sentences. Yet, there is a possible confounding between the effect of negation itself and the associative interference of two conflicting predicates - the original and the modified one - in negative trials. To avoid this, Experiment 2 modified the paradigm by including a story describing the activities of two protagonists in such a way that the affirmed and denied verification sentences had the same content, and only differed in the attribution of a specific event to the correct or wrong protagonist. The negation-induced forgetting effect was still powerful, while controlling for potential contaminating variables. Our finding would support that the impaired long-term memory could be ascribed to reusing the inhibitory mechanism of negation.