Working memory and focal attention.

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.

Covert attention accelerates the rate of visual information processing.

Whenever we open our eyes, we are confronted with an overwhelming amount of visual information. Covert attention allows us to select visual information at a cued location, without eye movements, and to grant such information priority in processing. Covert attention can be voluntarily allocated, to a given location according to goals, or involuntarily allocated, in a reflexive manner, to a cue that appears suddenly in the visual field. Covert attention improves discriminability in a wide variety of visual tasks. An important unresolved issue is whether covert attention can also speed the rate at which information is processed. To address this issue, it is necessary to obtain conjoint measures of the effects of covert attention on discriminability and rate of information processing. We used the response-signal speed-accuracy tradeoff (SAT) procedure to derive measures of how cueing a target location affects speed and accuracy in a visual search task. Here, we show that covert attention not only improves discriminability but also accelerates the rate of information processing.

Reading time evidence for enriched composition.

Verbs like 'begin' and 'enjoy' appear to semantically select a complement that expresses an activity or an event (Jackendoff, R. (1997). The architecture of the language faculty. Cambridge, MA: MIT Press; Pustejovsky, J. Cognition 41 (1991) 47; Pustejovsky, J. (1995). The generative lexicon. Cambridge, MA: MIT Press). When these verbs occur with a complement that does not directly denote either an activity or an event (e.g. '... began the book' or '... enjoyed the book'), the complement must be type-shifted from an object to an activity to conform to the verb's semantic restrictions. We report an experiment in which self-paced reading times were found to be longer for complements that required type-shifting than for complements that directly matched the semantic restrictions of the matrix verb. This finding is argued to provide on-line evidence for a type of enriched lexical processing posited in recent lexical semantic research.

Sentence comprehension is mediated by content-addressable memory structures.

Studies of working memory demonstrate that some forms of information are retrieved by a content-addressable mechanism (McElree & Dosher, 1989; McElree, 1996, 1998), whereas others require a slower search-based mechanism (McElree & Dosher, 1993). Measures of the speed and accuracy of processing sentences with filler-gap dependencies demonstrate that the probability of maintaining a representation of a filler item decreases as additional material is processed, but that the speed with which a preserved representation is accessed is unaffected by the amount of interpolated material. These results suggest that basic binding operations in sentence comprehension are mediated by a content-addressable memory system.

Isolating the contributions of familiarity and source information to item recognition: a time course analysis.

Recognition memory may be mediated by the retrieval of distinct types of information, notably, a general assessment of familiarity and the recovery of specific source information. A response-signal speed-accuracy trade-off variant of an exclusion procedure was used to isolate the retrieval time course for familiarity and source information. In 2 experiments, participants studied spoken and read lists (with various numbers of presentations) and then performed an exclusion task, judging an item as old only if it was in the heard list. Dual-process fits of the time course data indicated that familiarity information typically is retrieved before source information. The implications that these data have for models of recognition, including dual-process and global memory models, are discussed.

Literal and figurative interpretations are computed in equal time.

The time courses for constructing literal and figurative interpretations of simple propositions were measured with the response signal, speed-accuracy tradeoff procedure. No differences were found in comprehension speed for literal and figurative strings in a task that required judging whether a string of words was meaningful. Likewise, no differences were found in processing speed for nonsense and figurative strings in a task that required judging whether a string of words was literally true. Figurative strings were less likely to be judged meaningful than were literal strings and less likely to be rejected as literally true than were nonsense strings. The absence of time-course differences is inconsistent with approaches to figurative processing that contend that a figurative interpretation is computed after an anomalous literal interpretation. The time-course profiles suggest that literal and figurative interpretations are computed in equal time but that the meaning of the latter is less constrained than that of the former.

The temporal dynamics of visual search: evidence for parallel processing in feature and conjunction searches.

Feature and conjunction searches have been argued to delineate parallel and serial operations in visual processing. The authors evaluated this claim by examining the temporal dynamics of the detection of features and conjunctions. The 1st experiment used a reaction time (RT) task to replicate standard mean RT patterns and to examine the shapes of the RT distributions. The 2nd experiment used the response-signal speed-accuracy trade-off (SAT) procedure to measure discrimination (asymptotic detection accuracy) and detection speed (processing dynamics). Set size affected discrimination in both feature and conjunction searches but affected detection speed only in the latter. Fits of models to the SAT data that included a serial component overpredicted the magnitude of the observed dynamics differences. The authors concluded that both features and conjunctions are detected in parallel. Implications for the role of attention in visual processing are discussed.

Accessing short-term memory with semantic and phonological information: a time-course analysis.

The time course for accessing short-term memory representations on the basis of item, phonological, and semantic information was measured with a speed-accuracy tradeoff (SAT) variant of a recognition probe task. Subjects studied 5-word lists and then judged whether a test word (1) was in the study list (item judgment); (2) rhymed with a word in the study list (rhyme judgment); or (3) was a synonym of a word in the study list (synonym judgment). Analysis of the SAT retrieval functions demonstrated that judgments based on phonological and semantic information were slower and less accurate than judgments based on composite item representations. The slower retrieval dynamics for rhyme and synonym judgments suggest that judgments based on component properties of the memory trace are mediated by either a generate or recall process distinct from the parallel or direct-access mechanism used in item judgments.