Changes in sustained attention, attentional selectivity, and attentional capacity were examined in a sample of 113 participants between the ages of 12 and 75. To measure sustained attention, we employed the sustained-attention-to-response task (Robertson, Manly, Andrade, Baddeley, & Yiend, Neuropsychologia 35:747-58, 1997), a short continuousperformance test designed to capture fluctuations in sustained attention. To measure attentional selectivity and capacity, we employed a paradigm based on the theory of visual attention (Bundesen, Psychological Review 97:523-547, 1990), which enabled the estimation of parameters related to attentional selection, perceptual threshold, visual short-term memory capacity, and processing capacity. We found evidence of agerelated decline in each of the measured variables, but the declines varied markedly in terms of magnitude and lifespan trajectory. Variables relating to attentional capacity showed declines of very large effect sizes, while variables relating to attentional selectivity and sustained attention showed declines of medium to large effect sizes, suggesting that attentional control is relatively preserved in older adults. The variables relating to sustained attention followed a U-shaped, curvilinear trend, and the variables relating to attentional selectivity and capacity showed linear decline from early adulthood, providing further support for the differentiation of attentional functions.

Despite frequent reports of poor concentration following traumatic brain injury, studies have generally failed to find disproportionate time-on-task decrements using vigilance measures in this patient group. Using a rather different definition, neuropsychological and functional imaging research has however linked sustained attention performance to right prefrontal function--a region likely to be compromised by such injuries. These studies have emphasised more transitory lapses of attention during dull and ostensibly unchallenging activities. Here, an existing attention measure was modified to reduce its apparent difficulty or 'challenge'. Compared with the standard task, its capacity to discriminate traumatically head-injured participants from a control group was significantly enhanced. Unlike existing functional imaging studies, that have compared a sustained attention task with a no-task control, in study 2 we used positron emission tomography to contrast the two levels of the same task. Significantly increased blood flow in the dorsolateral region of the right prefrontal cortex was associated with the low challenge condition. While the results are discussed in terms of a frontal system involved in the voluntary maintenance of performance under conditions of low stimulation, alternative accounts in terms of strategy application are considered.

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The processes of error awareness and sustained attention were investigated in 18 traumatic brain injury (TBI) individuals and 16 matched control participants. In Experiment 1, we found that: (1) in comparison to controls, TBI participants displayed reduced sustained attention and awareness of error during the Sustained Attention to Response Task; (2) degree of error awareness was strongly correlated with sustained attention capacity, even with severity of injury partialed out; and (3) that error feedback significantly reduced errors. We replicated the finding of a correlation between error awareness and sustained attention capacity in Experiment 2 with a separate sample of 19 TBI participants and 20 controls. We conclude that TBI leads to impaired sustained attention and error awareness. The finding of a significant relationship between these two deficits in TBI suggests there may be a link between these two processes. Feedback on error improves sustained attention performance of control and TBI participants.

The internal nature of visual imagery makes the measurement of visual imagery ability a difficult task. In this review, we describe and evaluate the available measures of visual imagery ability. Several questionnaires of vividness, control, and preference have received favorable psychometric evaluations but these were not created on the basis of a theoretical analysis of imagery ability. Recent development of questionnaires has taken account of theoretical advances. Future research should continue in this vein. Objective tests of spatial ability may not be as appropriate as theory-driven visual imagery tests, as measures of visual imagery ability. The latter should be standardized. The well-known finding of a lack of relationship between subjective and objective imagery measures has been challenged by recent findings. Before this relationship can be fully examined, current measurement should be improved.