Fragile associations coexist with robust memories for precise details in long-term memory.

What happens to memories as we forget? They might gradually lose fidelity, lose their associations (and thus be retrieved in response to the incorrect cues), or be completely lost. Typical long-term memory studies assess memory as a binary outcome (correct/incorrect), and cannot distinguish these different kinds of forgetting. Here we assess long-term memory for scalar information, thus allowing us to quantify how different sources of error diminish as we learn, and accumulate as we forget. We trained subjects on visual and verbal continuous quantities (the locations of objects and the distances between major cities, respectively), tested subjects after extended delays, and estimated whether recall errors arose due to imprecise estimates, misassociations, or complete forgetting. Although subjects quickly formed precise memories and retained them for a long time, they were slow to learn correct associations and quick to forget them. These results suggest that long-term recall is especially limited in its ability to form and retain associations.

Translating basic attentional paradigms to schizophrenia research: reconsidering the nature of the deficits.

Abnormalities in attention have long been viewed as one of the fundamental underlying cognitive deficits in schizophrenia, likely contributing both to formation of some types of symptoms and particularly to the substantial work and social impairments that often accompany schizophrenia. Yet, the precise nature of the attentional deficits in schizophrenia remains poorly understood. Translating advances in cognitive psychology to clinical research brings paradigms with greater analytic power to the study of attention in schizophrenia. In particular, these paradigms should shed light on whether the attentional dysfunction in schizophrenia is best conceptualized as arising from limitations in amount or allocation of processing capacity or from more specific structural bottlenecks that do not allow certain processes to be carried out in two tasks simultaneously. Certain types of dual-task paradigms are particularly well suited to make distinctive predictions, particularly those involving a psychological refractory period paradigm. The background and design of a series of ongoing studies of prodromal, first-episode, and chronic schizophrenia patients are described that are addressing the developmental course of attentional dysfunction in this disorder. These refined paradigms should substantially increase our understanding of the specific forms of attentional impairment characterizing schizophrenia and their connections to symptom development and functional outcome.

Moray revisited: high-priority affective stimuli and visual search.

Previous research offers conflicting suggestions about whether "high-priority" verbal stimuli such as an individual's own name or emotionally charged words automatically grab attention and/or can be detected without the usual capacity limitations. Nine experiments investigated this issue, using visual search through displays of words. In speeded search tasks, the subject's own name was detected more quickly than other targets, but in no case were search slopes flat enough to suggest parallel search or "pop-out". Further, names were not found to be unusually potent distractors. Emotionally charged words were neither more readily detected as targets nor more potent as distractors than neutral words. A comparison of observers' accuracy in searching briefly exposed simultaneous vs. successive displays provided further evidence that search for "high-priority" word targets is subject to the same severe capacity limitations as those that are found with search for neutral words.

Dual-task interference with equal task emphasis: graded capacity sharing or central postponement?

Most studies using the psychological refractory period (PRP) design suggest that dual-task performance is limited by a central bottleneck. Because subjects are usually told to emphasize Task 1, however, the bottleneck might reflect a strategic choice rather than a structural limitation. To evaluate the possibility that central operations can proceed in parallel, albeit with capacity limitations, we conducted two dual-task experiments with equal task emphasis. In both experiments, subjects tended to either group responses together or respond to one task well before the other. In addition, stimulus-response compatibility effects were roughly constant across stimulus onset asynchronies (SOAs). At the short SOA, compatibility effects also carried over onto response times for the other task. This pattern of results is difficult to reconcile with the possibility that subjects share capacity roughly equally between simultaneous central operations. However, this pattern is consistent with the existence of a structural central bottleneck.

Concurrent task effects on memory retrieval.

Previous studies combining continuous free recall with a concurrent task have generally shown that concurrent tasks impose fairly negligible effects on memory retrieval. By contrast, dual-task studies employing either cued recall or semantic retrieval reveal gross memory impairment and suggest that retrieval is delayed by the centrally demanding phase of the concurrent tasks (i.e., response selection). To explore this conflict, subjects performed continuous free recall while carrying out a serial-choice-response time (RT) task, as in the previous free recall studies. Unlike these previous studies, however, the choice-RT task utilized arbitrary stimulus-response mappings in order to increase the proportion of time devoted to the centrally demanding response selection phase. Recall total was reduced significantly, and recall latency was slowed substantially.