Uncertainty about the rest of the sentence

A word-by-word human sentence processing complexity metric is presented. This metric formalizes the intuition that comprehenders have more trouble on words contributing larger amounts of information about the syntactic structure of the sentence as a whole. The formalization is in terms of the conditional entropy of grammatical continuations, given the words that have been heard so far. To calculate the predictions of this metric, Wilson and Carroll's (1954) original entropy reduction idea is extended to infinite languages. This is demonstrated with a mildly context-sensitive language that includes relative clauses formed on a variety of grammatical relations across the Accessibility Hierarchy of Keenan and Comrie (1977). Predictions are derived that correlate significantly with repetition accuracy results obtained in a sentence-memory experiment (Keenan & Hawkins, 1987).     

The effects of the dopamine D1 receptor antagonist SCH23390 on memory reconsolidation following reminder-activated retrieval in day-old chicks

This series of experiments examined the involvement of the dopamine D1 receptor antagonist, SCH23390, on memory reconsolidation following reminder-activated retrieval. Day-old male New HampshirexWhite Leghorn chicks were trained on a single trial passive avoidance task. A dose of 0.5 mg/kg of SCH23390 was administered subcutaneously 5 min before reminder trials, which were presented at 30, 60, and 90 min following training. Memory deficits were observed when reminder trials were presented at 30 and 60 min following training, but not when a reminder was presented at 90 min. No effect on memory retention was observed when reminder trials were not presented, suggesting that reconsolidation mechanisms were both contingent on the presentation of the reminder and independent of the consolidation process. Following a reminder presented at 60 min post-training, deficits in memory retention emerged between 45 and 60 min. The deficit was prolonged, lasting for up until 48 h after reminder presentation. The results indicate an important role for the D1 receptor in reconsolidation processes.     

Variations in working memory capacity predict individual differences in general learning abilities among genetically diverse mice

Up to 50% of an individuals' performance across a wide variety of distinct cognitive tests can be accounted for by a single factor (i.e., "general intelligence"). Despite its ubiquity, the processes or mechanisms regulating this factor are a matter of considerable debate. Although it has been hypothesized that working memory may impact cognitive performance across various domains, tests have been inconclusive due to the difficulty in isolating working memory from its overlapping operations, such as verbal ability. We address this problem using genetically diverse mice, which exhibit a trait analogous to general intelligence. The general cognitive abilities of CD-1 mice were found to covary with individuals' working memory capacity, but not with variations in long-term retention. These results provide evidence that independent of verbal abilities, variations in working memory are associated with general cognitive abilities, and further, suggest a conservation across species of mechanisms and/or processes that regulate cognitive abilities.     

Effects of age and interpersonal contact on stereotyping of the elderly

The purpose of this study was to examine the relationship between the age of an individual, the type of contact an individual has with the elderly, the amount of knowledge an individual has about the elderly, and the extent that the individual stereotypes the elderly. In accordance with the Social Identity Theory and the Contact Hypothesis, stereotyping was predicted to be higher among individuals who did not identify with nor have contact with the elderly. Fifty young (18-25 years of age) and fifty elderly (64-79 years of age) participants completed surveys measuring their level of contact with the elderly, knowledge about aging (knowledge score), and tendency to stereotype the elderly (stereotype score). Results of this study indicated that regardless of age, participant knowledge of aging and application of aging stereotypes were affected by the quality of contact experienced. Although the young participants achieved significantly higher knowledge scores than the elderly participants, there was no significant age difference in stereotype scores for the young and elderly groups. However, as predicted, the young and elderly participants who experienced high levels of contact with the elderly achieved higher knowledge scores and lower stereotype scores. These scores were compared to the respective scores of the young and elderly participants experiencing low levels of contact with the elderly. Moreover, the elderly participants experiencing low levels of contact with the elderly achieved lower knowledge scores than any of the other groups. Elderly participants experiencing low levels of contact with other competent elderly individuals may be more susceptible to the negative effects of aging stereotypes and at risk for not identifying with their own social group.     

The information-loss model: a mathematical theory of age-related cognitive slowing

A model of cognitive slowing is proposed with the following assumption: Information is lost during processing, processing occurs in discrete steps with step duration inversely related to the amount of information currently available, and the effect of aging is to increase the proportion of information lost per step. This model correctly predicts a positively accelerated relation between latencies of older and younger adults and provides a unified account of the effects of task complexity, practice, speed-accuracy tradeoffs, and fluctuations in individual performance. Strong support for the thesis that cognitive slowing is global, and not localized in specific age-sensitive components, is provided by the fact that the model accurately predicts the latencies of older adults on the basis of those of younger adults, without regard to the nature of the task, across a latency range of nearly 2 orders of magnitude.     

Repetition effects in word and pseudoword identification: comment on Salasoo, Shiffrin, and Feustel

Two recent articles by Feustel, Shiffrin, and Salasoo (1983) and Salasoo, Shiffrin, and Feustel (1985) argue that word identification is based on episodic memory as well as semantic (or "permanent, abstract") memory. The earlier article argued for separate processing stages affected by repetition (episodic memory) and lexicality (semantic memory). To account for the new finding that number of repetitions interacts with lexicality, the later article invokes the same two types of memory, operating in parallel rather than serially. We argue that Salasoo et al.'s data are compatible with a wide variety of competing theories, including some that do not involve episodic memory at all. We question the relevance of a complex formal model shown by the authors to account for the main trends in the data, because it makes little use of key properties of episodic memory. Furthermore, we show that two variants of a less complex model inspired by logogen theory fit the data as well or better than the model of Salasoo et al., using fewer free parameters. We argue that what is needed is not an existence proof that one particular complex model can fit a body of data, but experimental manipulations that successfully discriminate between broad classes of competing theories.