Subjects viewed sequentially presented lists of 3-6 words, which were followed by a recognition probe. Memory retrieval speed (dynamics) and strength were measured in an interruption speedaccuracy trade-off (SAT) procedure and a collateral reaction time (RT) procedure. In SAT, item strengths depended on serial position, but only two retrieval speeds were observed: a fast rate for the last item in the study list (a case of immediate repetition between study and test) and a slow rate for all other items that was independent of serial position and set size. Serial-positiondependent strengths and set-size-dependent criterion shifts accounted for standard RT patterns that have been taken as evidence for serial scanning in short-term memory. Summary of ExperimentsWe examined retrieval in immediate memory for short lists, using speed-accuracy trade-off (SAT) and comparable reaction time (RT) paradigms. We replicated MonselFs (1978) demonstration of strong recency or serial position effects on RT, which average to produce linear, parallel set size functions for both positive and negative trials. In SAT, memory strength or probability (indexed by asymptotic accuracy) and retrieval speed (indexed by rate and intercept) were separately estimated for full retrieval functions. An SAT experiment showed that the serial position effects in RT are paralleled by analogous effects on asymptotic memory strength. The dynamics of retrieval (rate and intercept) were equal for all serial positions except the most recent and were independent of set size. There was a large speeding in retrieval when the test item was the same as the last list member (immediate repetition), which is a replication of a similar finding by Wickelgren, Corbett, and Dosher (1980) in long lists. Thus observed SAT rate differences between set sizes when serial position data were pooled reflected the relative proportion of immediate repetitions in different set sizes. Set size per se had no effect on retrieval speed, although different serial position mixes resulted in different asymptotic accuracy. The immediate repetition effect did not depend on a physical match between the last list element and the test. All results were replicated in a second SAT experiment, in which we presented list items in lowercase letters and test items in uppercase letters. In that experiment we also examined the effect of recency on negative trials. Recent negatives (items presented in the immediately previous memory list) yielded higher false alarms than did distant negatives, especially early in retrieval. Serial-scanning

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Measures of retrieval speed indicated that only a small subset of representations in working memory falls within the focus of attention. An n-back task, which required tracking an item 1, 2, or 3 back in a sequentially presented list, was used to examine the representation and retrieval of recent events and how control processes can be used to maintain an item in focal attention while concurrently processing new information. A speed-accuracy trade-off procedure was used to derive measures of the availability and the speed with which recent events can be accessed. Results converge with other time course studies in demonstrating that attention can be concurrently allocated only to a small number of memory representations, perhaps just 1 item. Measures of retrieval speed further demonstrate that order information is retrieved by a slow search process when an item is not maintained within focal attention.Many core operations in complex cognitive tasks depend on the by-products of recent perceptual and cognitive processing. In language comprehension, for example, a reader/ listener is frequently required to resolve long-distance dependencies in which a constituent assigns a grammatical and semantic role to a representation of a phrase processed at a much earlier point in the sentence (e.g., McElree, 2000). Similarly, subgoals in reasoning and problem solving often require access to the products of operations applied in earlier subgoals (e.g., Anderson, 1983).The amount of information that can be processed at one time is limited, and, in many cases, it is unlikely that all the relevant by-products of recent processing can be actively maintained in the focus of attention. Whenever information exceeds the span of attention, successful execution of a cognitive operation requires shunting information between memory and focal attention. The span of attention places constraints on possible cognitive operations and the manner in which various mental computations must be performed. Determining the capacity of focal attention and how focal attention interfaces with different memory systems is an essential part of understanding complex cognitive tasks.The experiments reported here use the n-back task (Awh et al., 1996;Cohen et al., 1994Cohen et al., , 1997Dobbs & Rule, 1989;See & Ryan, 1995; to examine how much information can be maintained in focal attention while concurrently processing new information. Additionally, the task was used to examine the closely related issue of how information is shunted between memory and focal attention when attentional capacity is exceeded. The n-back task requires judging whether an item matches the nth-item back (e.g., 1-back, 2-back, 3-back) in a sequentially presented list of items. It challenges individuals to maintain the n-back item in focal attention while concurrently processing new items. Substantial demands are placed on control (executive) processes, because the response set NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript must be continually updat...

The role of interference effects in sentence processing has recently begun to receive attention, however whether these effects arise during encoding or retrieval remains unclear. This paper draws on basic memory research to help distinguish these explanations and reports data from an experiment that manipulates the possibility for retrieval interference while holding encoding conditions constant. We found clear support for the principle of cue-overload, wherein cues available at retrieval cannot uniquely distinguish among competitors, thus giving rise to interference effects. We discuss the data in relation to a cue-based parsing framework (Van Dyke & Lewis, 2003) and other interference effects observed in sentence processing (e.g., Gordon, Hendrick, & Johnson, 2001, 2004. We conclude from the available data that the memory system that subserves language comprehension operates according to similar principles as memory in other domains.