Alzheimer's disease disrupts arithmetic fact retrieval processes but not arithmetic strategy selection

Three groups of healthy younger adults, healthy older adults, and probable AD patients, performed an addition/number comparison task. They compared 128 couples of additions and numbers (e.g., 4 + 9 15) and had to identify the largest item for each problem by pressing one of two buttons located under each item. Manipulations of problem characteristics (i.e., problem difficulty and splits between correct sums and proposed numbers) enabled us to examine strategy selection and specific arithmetic fact retrieval processes. Results showed that arithmetic facts retrieval processes, which were spared with aging, were impaired in AD patients. However, AD patients were able to switch between strategies across trials according to problem characteristics as well as healthy older adults, and less systematically than healthy younger adults. We discuss implications of these findings for further understanding AD-related differences in arithmetic in particular, and problem solving in general.     

Simon congruency effects based on stimulus and response numerosity

Three choice reaction time experiments documented a Simon-type congruence effect involving the numbers of stimuli and responses. In Experiment 1 the stimulus consisted of one or two high- or low-pitch tones, and participants were required to respond with one or two taps of a response key depending on stimulus pitch. Responses were faster when the number of tones matched the required number of response taps than when these numbers mismatched. Experiment 2 showed that a weaker version of this effect can also be obtained using visual stimuli, and Experiment 3 showed that the analogous effect can even be obtained, albeit very weakly, with bimodal stimuli. There was also evidence that the number of stimuli affected the rate of emitting the two-tap response. These results indicate that stimulus numerosity is processed automatically to the level at which it can affect the selection and possibly the execution of a varying number of responses.     

Goal congruency without stimulus congruency in bimanual coordination

Two experiments explored the role of stimulus congruency and goal congruency for the generation of object-oriented actions with two hands. Participants had to place two objects into either parallel or opposite orientations by carrying out either symmetrical or asymmetrical forearm rotations. Performance was superior when the required object orientations were identical rather than different, almost independent of the symmetry of the required arm movements. In extending previous research, goal congruency effects ensued even under conditions in which congruency of imperative response signals could not have contributed to goal congruency effects, either because only a single stimulus was used to indicate the required goals in an individual trial (Experiment 1) or such stimuli were absent at all (Experiment 2). The results thus confirm the importance of goal codes for the reconcilableness of bimanual actions, and rule out accounts in terms of stimulus-related processes.     

Procedural knowledge versus fact retrieval in mental arithmetic: A reply to Baroody

Based on a review of reaction time studies, a model of mental arithmetic performance which emphasizes the process of fact retrieval from organized memory representations was proposed (M. H. Ashcraft, Developmental Review, 1982, 2, 213–236). In contrast to this view A. J. Baroody (Developmental Review, 1983, 3, 225–230) proposes that most mental arithmetic performance depends on procedural knowledge such as rules, heuristics, and principles. While Baroody's idea is both intriguing and potentially important, its exposition is quite vague and speculative. Without concrete suggestions as to the nature of the proposed rules and heuristics, especially for routine problems like 4 + 3 and 8 × 5, Baroody's proposal appears to be pertinent only to special cases like N + 0 and N + 1. Lacking this sort of elaboration, the alternative does not provide a useful or compelling explanation of the existing Chronometric results, and seems, at best, to be premature.     

Effect of time of day on arithmetic fact retrieval in a number-matching task

The goal of this study is aimed to investigate a possible effect of time of day on arithmetic fact retrieval in a number-matching task. We tested 96 students (age range 19-33 years) at 9 a.m. and at 1 p.m., in a counterbalanced order. The subjective alertness levels were also recorded. As regards retrieval efficiency, the results showed that the sum interference effect was significantly more pronounced in the morning (9 a.m.) than at midday (1 p.m.). As expected, participants showed higher subjective alertness levels at 1 p.m. than at 9 a.m.. However, the difference of subjective alertness did not completely explain differences in interference at two testing sessions. The results could be explained with respect to the variation of working memory efficiency during the day.     

Rote memory and arithmetic fact processing

The goal of the study was to examine the part played by skill in memorizing arbitrary sequences in the efficiency with which normal young adults perform simple arithmetic fact problems. The first experiment showed a clear independent role for sequence memory in all arithmetic fact processing, but a lesser role for semantic retrieval. This result was particularly true for large-answer multiplication problems and subtraction and division problems with large first operands. In a second experiment, which included a visuomotor processing control task, sequence memory predicted processing of all arithmetic problems apart from small additions independently of semantic retrieval, with the most robust independent contribution being to large-answer multiplication problems. The results, which are compatible with Dehaene and colleagues' triple-code model, suggest that rote learning may be a successful way for some people to process arithmetic facts efficiently.     

Models of arithmetic fact retrieval: an evaluation in light of findings from normal and brain-damaged subjects.

Retrieval of basic arithmetic facts is a central aspect of almost any arithmetic performance. Furthermore, the arithmetic facts provide an opportunity to study memory processes in the context of a naturally occurring but circumscribed set of facts. This article examines current models of arithmetic fact retrieval in light of previously reported data from normal subjects, as well as the results from brain-damaged patients reported by Sokol, McCloskey, Cohen, and Aliminosa (1991) in the preceding article. The discussion serves to delineate the strengths and limitations of the models and, more generally, to identify important theoretical and empirical issues in the study of arithmetic fact retrieval.     

Focused memory search in fact retrieval

Several studies of fact retrieval have shown that the more facts a person learns about a concept, the longer it takes him or her to retrieve any of these facts. This result has been interpreted to mean that retrieval of a fact about a concept involves a search of all facts stored in memory with that concept. In the present study, it is suggested that retrieval involves not an unfocused search of all facts stored with a concept, but rather a focused memory search that examines relevant stored facts and ignores irrelevant information. This argument is supported by three experiments in which subjects first learned simple facts (e.g., “The banker likes horses”) and then made speeded true-false decisions for test probes le.g., “The banker likes elephants”). Specifically, results suggest that facts stored with a concept may be organized into subsets. For example, a person’s knowledge about Richard Nixon might be organized into subsets concerning Nixon’s resignation, his trips to China, his family, and so on. The data further suggest that a person attempting to retrieve a fact about a concept (e.g., the name of Nixon’s wife) may simply decide which subset is most likely to contain the desired fact (e.g., the subset concerning Nixon’s family) and search that subset. If the sought-for fact is found in this subset, the search process terminates. If, however, the desired information is not located, other subsets of facts may be searched before the retrieval attempt is given up. The notion that memory search focuses on relevant stored facts and ignores irrelevant information may help to explain why experts (i.e., people who know a large number of facts about a topic) do not experience great difficulty in retrieving facts in their areas of expertise.     

Extinction of avoidance in rats: response availability and stimulus presentation effects

A conditioned a versive stimulus presented in prolonged, continuous fashion is said to be flooded. Using a two-way shuttle avoidance task. Polin (1959) found that animals allowed to respond to flooded stimuli extinguish faster than animals prevented from responding to discrete stimuli of equal total duration. But, as Shearman (1970) noted, the CS presentation and response availability factors were confounded. He arranged them factorially, in a 2 × 2 design, again utilizing two-way avoidance, but found no differences between any of the experimental groups, although all groups extinguished faster than a regular extinction control group, the only group for which CS termination was response-contingent. Since there is evidence from one-way avoidance studies that response prevention facilitates extinction of avoidance with CS exposure held constant (Shipley et al., 1971). we repeated the Shearman design, using a one-way avoidance paradigm, and including a group for whom the aversive CS would be presented in discrete trials at increasing intensities. A separate aspect of the present investigation concerned the measurement of a fear response as well as the avoidance response. Results of several investigations have shown (e.g. Coulter et al. 1969; Linton et al.. 1970) that avoidance behaviour can be extinguished without the extinction of fear. It was thought useful to assess the generality of this result, since in two-factor theory, fear and avoidance are related.Two supplementary experiments replicated important conditions of the initial one, while examining whether response prevention and response non-availability have similar effects (II), and the relation between the fear test and the test for extinction (III).     

Facts, rules, and procedures in normal calculation: evidence from multiple single-patient studies of impaired arithmetic fact retrieval.

This article presents results from multiple single-case studies of brain-damaged patients with impairments in retrieval of arithmetic facts (i.e., "table" facts such as 8 x 7 = 56). The results provide a basis for exploring the types of knowledge implicated in simple arithmetic performance, the internal representations for the various knowledge types, the processes operating upon these representations, and the ways in which the representations or processes may be disrupted by brain damage.     

Modeling graded response congruency effects in task switching

Compound cue retrieval is a computational model of a mediated route for response selection in task-switching situations. In previous studies, the model has been shown to account for response congruency effects when switching between two tasks, where response congruency reflects the degree of match between relevant and irrelevant task responses associated with a target stimulus. In the present study, the author derived a model prediction of graded response congruency effects in situations involving three tasks. The predicted pattern was observed for both response time and error rate in an experiment in which numerical categorization tasks were performed on single-digit targets. Implications for understanding response congruency effects and for developing models of task-switching performance are discussed.     

The impact of stimulus-specific practice and task instructions on response congruency effects between tasks

In task switching experiments participants have to respond to the same set of stimuli while task instructions vary (e.g., digit stimuli are assigned to left- or right-sided key presses by means of magnitude vs. parity classification). Response congruency effects denote worse performance for a stimulus, which is associated with different responses in the two tasks as compared to a stimulus, which is associated with the same response. Previous research suggests that such effects reflect direct links between stimuli and responses acquired in the course of experimental practice. In the current study we investigated the impact of stimulus-specific practice and task instruction by reversing the S–R mapping of one task (Experiment 1) or replacing one task with a new one (Experiment 2) in the second half of an experimental session. Consistent with the direct link account, S–R links practiced during the first half of the experiment largely determined congruency effects despite altered task instructions. Furthermore, the results suggest that previously practiced S–R links (a) can be relatively quickly overwritten by practicing a novel S–R mapping, and (b) are subject to passive decay when no longer in use.     

A perceptual comparison between paired stimulus and single stimulus methods of presentation of the fluent utterances of stutterers

This investigation compared tape recordings containing the fluent utterances of treated stutterers with those of normal speakers as paired stimuli and single stimuli as presented to 20 sophisticated judges. Fluent utterances were obtained from stutterers successfully treated in one of the following programs: (1) Van Riperian, (2) metronome-conditioning speech retraining, (3) delayed auditory feedback, (4) operant conditioning, (5) precision fluency shaping program, and (6) holistic therapy. In addition, a group of partially treated stutterers were included. The original tape recordings containing matched samples of the fluent utterances of a stutterer and normal speaker were presented as paired stimuli. These paired samples were then separated, randomized, and assembled individually on another tape recording and presented as single stimuli to the same judges. The results of the statistical analysis indicated that the fluent utterances of treated stutterers was perceptibly different from the fluent utterances of nonstutterers, regardless of the method of stimulus presentation.     

Sensory and meaning features in stimulus recognition and associative retrieval.

Three experiments addressed the problem of isolating the effects of sensory similarity on subprocesses involved in coding paired associates. In the first, the standard recognition-recall procedure was used and stimulus similarity, concreteness, and frequency were varied. However, because of concern with the validity of this recognition procedure as a measure of functional stimulus contact, an alternative was developed. This alternative led to the second study in which only stimulus similarity was manipulated. In the third experiment, similarity was varied, and the pairs were either associatively compatible, unrelated, or incompatible. The results using the new procedure indicated that similarity consistently disrupted functional stimulus contact but not associative retrieval. By contrast, associative relatedness facilitated both subprocesses.     

Relationship between the presentation of the MOMMY AND I ARE ONE stimulus and mood.

In 1992 Weinberger suggested the effects of the presentation of MOMMY AND I ARE ONE might be mediated by its capacity to produce positive mood changes. Later support for this idea is unconvincing because these experiments lack the converging operations required to support the assumption that participants can encode the complete meaning of MOMMY AND I ARE ONE. Furthermore, without justification, they bypassed several variables of importance in prior research. Wide acceptance of findings in this area requires convincing evidence that participants can encode much more information from MOMMY AND I ARE ONE than from other types of subliminal stimuli and from supraliminal stimuli presented briefly. Until such evidence is available. attempts to explore individual differences in neurophysiological responses to MOMMY AND I ARE ONE, after it has been assumed to be encoded, are premature.