Extracting parity and magnitude from Arabic numerals: developmental changes in number processing and mental representation.

Children from Grades 2, 3, 4, 6, and 8 (7.8, 9.2, 9.8, 11.7, and 13. 6 years old, respectively) made speeded, bimanual parity (odd/even) judgments of the Arabic numerals 0-9. Analysis of response times indicated that from fourth grade on, parity information is retrieved directly from memory rather than being extracted by means of a mental calculation strategy. As early as Grade 3, children exhibited the SNARC (Spatial-Numerical Association of Response Codes) effect, where small numbers were responded to faster with the left hand than with the right hand, while the converse held true for large numbers. This finding, previously demonstrated only in adults, confirms that (a) children represent magnitude information in the form of a left-to-right oriented mental number line, and (b) this information is accessed obligatorily even when irrelevant. Finally, although the SNARC effect remained strong at Grade 4, it was attenuated at Grades 6 and 8 by a linguistic effect based on associations between the unmarked adjectives "even" and "right" and between the marked adjectives "odd" and "left."

Directed forgetting deficits in patients with temporal lobe epilepsy: an information processing perspective.

Although mesial temporal lobe brain damage is frequently associated with memory loss, it is unclear whether the deficit results entirely from a disruption in the processing of relevant information or whether it also reflects interference from irrelevant information. Directed forgetting is one procedure that can be used, along with standard tests of memory, to investigate this distinction. Seventeen patients with a diagnosis of complex-partial seizures of temporal lobe origin and 17 healthy volunteers were compared on lexical decision, free recall, and recognition tests in a directed-forgetting paradigm. These tests created a memory profile to measure the influence of task relevant and irrelevant information in implicit and explicit memory. Compared with healthy volunteers, the patients were significantly impaired on the memory tasks overall [F(5,25) = 5.01, p < .01]. Specifically, directed forgetting in lexical decision and recognition both discriminated between the groups [stepdown F(1,26) = 6.84, eta 2 = .26, p < .05 and stepdown F(1,25) = 5.36, eta 2 = .13, p < .05, respectively]. The results suggest that interictal memory performance in temporal lobe epilepsy may be disrupted in part because of a deficit in the differential processing of task relevant and task irrelevant information, particularly at retrieval.

The Corsi block-tapping task: methodological and theoretical considerations.

The Corsi block-tapping task has enjoyed extensive use in clinical and experimental studies for a quarter of a century and is arguably the single most important nonverbal task in neuropsychological research. Nevertheless, there has been considerable inconsistency not only in the administration and scoring of this measure, but also in the physical properties of the test apparatus. In this paper, we survey a wide range of studies that have made use of the block-tapping task during the past 25 years and provide a detailed appraisal of the manifold methodological variations. Additionally, we discuss the historical context in which the Corsi originated and offer a critical examination of the cognitive processing operations purported to underlie performance on this task.

Capacity limitations of a classic M-power measure: a modified dual-task approach.

A modified dual-task approach was employed with 7- to 9-year-olds in an effort to determine whether one of the classic M-power measures, the digit placement task, is indeed capacity-limited. To this end, a computerized version of a three-item digit placement task was administered in addition to three other computerized tasks: a four-item digit placement task, simple reaction time (RT) to a tone presented alone, and reaction time to a tone occurring during the performance of another three-item digit placement task. Careful examination of the data revealed that several critical assumptions concerning the use of the dual-task procedure were successfully met. This permitted a test of the extent to which dual-task RTs were predictive of accuracy in the harder, four-item digit placement task. Not only was this relationship significant, but after partialling out other possible sources of variance, a significant correlation remained, indicating that the digit placement task is indeed capacity-limited.

Developmental changes in memorial comparisons: the effects of stimulus presentation mode.

First graders, fifth graders, and college students made comparative size judgments of either pictures (line drawings) or names (spoken words) of common objects by designating the "bigger" item in real life. Care was taken to equate the picture and word conditions on a number of critical parameters including method of item-pair presentation and activation of response-time intervals. All groups exhibited a symbolic distance effect. While judgments were faster with pictures than words, the magnitude of the difference did not change with age. Previous research suggesting a marked developmental decline in the magnitude of the "pictorial superiority effect" may have confounded reduced memory demands with stimulus presentation mode for young children. Finally, slopes of the symbolic distance functions were found to decrease with increasing grade level, at least from first to fifth grade. This is the first demonstration of an age-related decline in slopes for magnitude comparisons of concrete objects.

Phenylketonuria and complex spatial visualization: an analysis of information processing.

Recent neuropsychological studies have suggested that patients with early-treated phenylketonuria (PKU) and normal intelligence have a specific deficiency in solving complex spatial problems. In the present study a task involving the assembly of various shapes was used to compare the performance of 16 PKU patients and 11 sibling controls. Error rates generally were higher and response times slower among the PKU patients, but greater complexity did not produce differential changes in accuracy or speed in the PKU group compared to the controls. Correlations between task performance and IQ measures were significant for the PKU patients, but when IQ was controlled for the group differences vanished. The results suggest that choice of problem-solving strategy, attention span and accuracy of mental representation may be affected in PKU patients, despite efforts to maintain well-controlled phenylalanine concentrations in the blood.

The role of spatial cues in the probe-type serial memory task.

2 experiments were carried out with the aim of clarifying the role of spatial cues in the probe-type serial memory task devised by Atkinson, Hansen, and Bernbach. In experiment 1, preventing the formation of specific items-location associations drastically reduced performance at the early to intermediate serial positions for a group of second graders; yet these children still exhibited a primancy effect (position 1 greater than position2). In experiment 2, the stimulus items were spaced farther apart than usual in an attempt to reduce the contextual uniqueness of the first (far left) item. Children aged 4 and 5 years who were administered this task produced a serial-position function that was essentially flat. It was concluded that (a) spatial cues serve as functional stimuli in the standard probe-type task, and (b) the contextual uniqueness of the first item is probably responsible for the occurrence of primacy in young children. Implications of this research for interpreting age-related differences in the shape of the serial-position curve were also discussed.