Signal intrusion reconciles divergent effects of perceptual distraction on working memory

Perceptual distraction distorts visual working memories. Recent research has shown divergent effects of distraction on memory performance, including attractive or repulsive biases in memory reports, improving or impairing memory precision, and increasing or decreasing guess rates. These effects are sensitive to target-distractor similarity and thus have been attributed to sensory interference according to the sensory recruitment hypothesis of working memory. Here, we propose a novel Distractor Intrusion Model (DIM), an extension of the Target Confusability Competition (TCC) framework, to reconcile the discrepant results of perceptual distraction. We hypothesized that sensory interference, in all instances, is driven by the integration of a target memory signal and an intrusive distractor signal. We tested this model against the classical mixture model and other candidate models. Model comparisons showed that TCC-DIM had a superior fit to memory error distributions across six delay-estimation tasks with distraction (N = 220). Both passive and active distraction tasks were examined and target-distractor similarity was varied between 18° and 153°. According to the model, distractor intrusions decreased along with target-distractor similarity, in accordance with the sensory recruitment hypothesis. Moreover, we found that TCC-DIM successfully replicated divergent effects of distraction on memory bias, precision, and guesses using only this one intrusion mechanism. This model also makes a novel, and somewhat surprising, prediction that low-fidelity memories are likely to benefit from distractor intrusions, whereas high-fidelity memories are likely to become impaired. Our data support this prediction such that participants (N=49) with lower memory precision benefited from distraction and showed a reduction in memory errors relative to no-distraction trials. Those with higher memory precision showed greater errors following distraction. These results collectively suggest that perceptual distractors affect working memories through signal intrusions, thus providing a unified mechanism to explain diverse and divergent effects of distraction on working memory performance.