Measuring attentional capacity
Date
1986
Authors
Weber, Alison Mary
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Studies of attentional function in normals and attentional problems in clinical populations, particularly closed head injury cases, strongly indicate that the crucial aspect of attentional difficulty is the limited amount of information a person can attend to or process within a given time. Within this context, the terms "attentional capacity" and "information processing capacity " are used interchangeably and are also very closely related to the concept of "working memory".
Despite the reported prevalence of attentional problems among brain-impaired people, there is a dearth of appropriate clinical measures of attention. Those that do exist are limited in that they assume intact motor and/or speech response capacity which many brain-impaired people lack and they measure too narrow a range of capacity to be useful across the full clinical spectrum. The aim of the present study was to develop a measure that covers the full range of attentional capacity and accommodates the response deficits common in clinical populations.
A measure called the Attentional Capacity Test (ACT) was developed in which processing demands are gradually increased across eight succeeding levels of difficulty. It
involves the person listening to a series of numbers, mentally counting how many tar get numbers occur, and reporting their answer at the end of the series. The answer is always somewhere from 1 to 10, making the response one of multiple-choice format. Because the response is in multiple-choice format and given after the processing demands of the series are finished, the response mode and speed can be adjusted to patient requirements without affecting the processing demands of the task.
The primary concern of the present study was to explore the validity of the ACT as a measure of information processing or attentional capacity. Using a sample of 64
normal young adults, performance on the ACT was compared to that on a relatively well-established measure of information processing, the Paced Auditory Serial Addition Test (PASAT), and also to a simple measure of working memory, the Digits Backward Test. Positive relationships between the ACT and both these tasks confirmed that the ACT measured attentional capacity. The fact that the ACT related only moderately to the PASAT may have been because the PASAT demands adding skill and quick vocal responses which the ACT does not. This interpretation was confirmed by finding that the PASAT was highly correlated to a measure of adding speed and accuracy while the ACT was only minimally related to this task. Passive memory span, as measured by the Digits Forward task, was not meaningfully related to performance on either the ACT or the PASAT.
The construct validity of the ACT was further confirmed by comparing the ACT performance of nine brain-impaired patients to staff ratings of their attentional functioning in everyday life. A positive relation between the two measures was found for seven patients with diffuse injury but not for two patients with focal damage.
The implications of these findings are discussed with reference to the future development of the ACT.