Gone for Good: Lack of Priming Suggests Early Perceptual Interference in Emotion-Induced Blindness

Emotional stimuli are perceptually prioritized to such a degree that they can cause people to miss seeing subsequent targets that appear in front of their eyes. It is unclear whether this effect (known as emotion-induced blindness) reflects post-perceptual interference, in which case unseen targets might still impact later responses, as in the seemingly similar “attentional blink”. An alternative is that emotional distractors prevent target encoding, and so leave no residual trace of target information. In this study, we used a priming task to assess these alternative possibilities. Each emotion-induced blindness trial was immediately followed by a speeded arrow judgement task, in which the arrow’s orientation could be congruent or incongruent with the orientation of an emotion-induced blindness target. Analyses revealed strong evidence that seen targets primed the arrow judgment, but there was moderate to strong evidence that unseen targets elicited no priming whatsoever. These results lend support to claims that emotion-induced blindness reflects failure to perceptually encode target information, and so reflects a different mechanism from the phenomenally similar attentional blink.

Visual Long-term Memory Can Replace Active Maintenance in Visual Working Memory

Humans have remarkable visual long-term memory abilities, capable of storing thousands of objects with significant detail. However, it remains unknown how such memory is utilized during the short-term maintenance of information. Specifically, if people have a previously encoded memory for an item, how does this affect subsequent working memory for that same item? Here, we demonstrate people can quickly and accurately make use of visual long-term memories and therefore maintain less perceptual information actively in working memory. We assessed how much perceptual information is actively maintained in working memory by measuring neural activity during the delay period of a working memory task using electroencephalography. We find that despite maintaining less perceptual information in working memory when long-term memory representations are available, there is no decrement in memory performance. This suggests under certain circumstances people can dynamically disengage working memory maintenance and instead use long-term memories when available. However, this does not mean participants always utilize long-term memory. In a follow-up experiment, we introduced additional perceptual interference into working memory and found participants actively maintained items in working memory even when they had existing long-term memories available. These results clarify the kinds of conditions under which long-term and working memory operate. Specifically, working memory is engaged when new information is encountered or perceptual interference is high. Visual long-term memory may otherwise be rapidly accessed and utilized in lieu of active perceptual maintenance. These data demonstrate the interactions between working memory and long-term memory are more dynamic and fluid than previously thought.

Recognition Memory Shielded from Semantic but not Perceptual Interference in Normal Aging

Normal aging impairs long-term declarative memory, and evidence suggests that this impairment may be driven partly by structural or functional changes in the medial temporal lobe (MTL). Theories of MTL memory function therefore make predictions for age-related memory loss. One theory – the Representational-Hierarchical account – makes two specific predictions. First, recognition memory in older participants should be impaired by feature-level interference, in which studied items contain many shared perceptual features such that those features appear repeatedly. Second, if the interference in a recognition memory task – i.e., the information that repeats across items – resides at a higher level of complexity than simple perceptual features, such as semantic gist, older adults should be less impacted by such interference than young adults. We tested these predictions using the Deese-Roediger-McDermott paradigm, by creating feature-level (i.e., perceptual) interference with phonemically/orthographically related word categories, and higher-level associative interference with semantically related word categories. Importantly, we manipulated category size in order to compare the effect of less versus more interference (i.e., small versus large category size), which served to (1) avoid potential item confounds arising from systematic differences between words belonging to perceptually- versus semantically-related categories, and (2) ensure that any effect of interference was due to information encoded at study, rather than pre-experimentally. Further, we used signal detection theory to interpret our data, rather than examining false alarm rates in isolation, thereby avoiding potentially confounding contamination of the memory measure by changes in response bias across conditions or groups. Older participants, relative to young adults, were relatively more impaired by perceptual interference and less impaired by semantic interference. This pattern seems at odds with many current theories of age-related memory loss, but is in line with the Representational-Hierarchical account.