Habitual Task Research Articles

Naturalistic prospective memory in older adults: Predictors of performance on a habitual task

Age-related difficulties in episodic prospective memory (PM) are common. However, little is known about habitual PM, which involves remembering to carry out intended actions that are regular and repeated. This is important for many health-related tasks and for maintaining independence in daily living activities. This study investigates, in older people, the predictors of habitual PM performance in a naturalistic setting. A group of 191 community-based, older adults (aged 65–89 years) wore an actigraph over two weeks. The habitual PM task involved pressing a button twice daily (Bed-time, Rise-time) on the actigraph. Accuracy of response was calculated for Bed-time and Rise-time, determined by light, movement, and diary data. The contribution of retrospective memory and executive function to PM performance was assessed. PM was more accurate at Bed-time compared to Rise-time (p < .01), and better in the first compared to the second week (p < .01). Retrospective memory contributed small but significant unique variance (β = .24) to PM accuracy. For older adults living in the community, both contextual factors (e.g., time of day) and retrospective memory are important for individuals’ ability to remember to perform daily tasks. This is relevant when planning interventions for maintaining independent living in ageing.

Allowing brief delays in responding improves event-based prospective memory for young adults living with HIV disease

Event-based prospective memory (PM) tasks require individuals to remember to perform an action when they encounter a specific cue in the environment, and they have clear relevance for daily functioning for individuals with HIV. In many everyday tasks, not only must the individual maintain the intent to perform the PM task, but the PM task response also competes with the alternative and more habitual task response. The current study examined whether event-based PM can be improved by slowing down the pace of the task environment. Fifty-seven young adults living with HIV performed an ongoing lexical decision task while simultaneously performing a PM task of monitoring for a specific word (which was focal to the ongoing task of making lexical decisions) or syllable contained in a word (which was nonfocal). Participants were instructed to refrain from making task responses until after a tone was presented, which occurred at varying onsets (0–1600 ms) after each stimulus appeared. Improvements in focal and nonfocal PM accuracy were observed with response delays of 600 ms. Furthermore, the difference in PM accuracy between the low-demand focal PM task and the resource-demanding nonfocal PM task was reduced by half across increasingly longer delays, falling from 31% at 0-ms delay to only 14% at 1600-ms delay. The degree of ongoing task response slowing for the PM conditions, relative to a control condition that did not have a PM task and made lexical decisions only, also decreased with increased delay. Overall, the evidence indicates that delaying the task responses of younger HIV-infected adults increased the probability that the PM relevant features of task stimuli were adequately assessed prior to the ongoing task response, and by implication that younger HIV infected adults can more adequately achieve PM goals when the pace of the task environment is slowed down.

Influence of errors in coordinate transformation due to uncertainties of the design matrix

Coordinate transformation between reference systems is a habitual task in geodetic sciences. Several transformation models and adjustment of observations algorithms have been explored. The most popular approach uses the well-known Ordinary Least Squares method (OLS) which seeks to estimate unknown parameters in a linear regression model by minimizing the sum of squared residuals while assuming that the observations are subject to normally distributed random noise. Although this approach has been widely used on many applications, its assumption regarding the distribution of errors is unrealistic. An alternative model created to deal with non normal–random distributions of errors is the Total Least Square model (TLS). Although several approaches have been suggested for representing the errors in the design matrix, most of them fail in including errors with different stochastic characteristics truthfully. This paper presents an assessment of the quality of a Helmert transformation of 2D coordinates when different precisions in both the observation vector and the design matrix exist. Two algorithms were analyzed: the OLS, and the Improved Weighted Total Least Squares (IWTLS). The transformation parameters obtained through IWTLS and OLS show significant differences among them when the variances in the coordinate systems are different. When assessing the transformation of coordinates using control points, it becomes clear that both algorithms perform the same in terms of the quality of the transformation. Furthermore, it is shown that an analysis based on the residuals obtained in the least squares adjustment is not a reliable tool to assess the overall quality of the transformation.

Task oriented visual satisfaction and wearing success with two different simultaneous vision multifocal soft contact lenses

Purpose A longitudinal prospective, cross-over, double masked study was designed to evaluate task oriented visual satisfaction and wearing success with two types of simultaneous vision multifocal soft contact lenses. Methods Twenty-two presbyopic subjects followed two 14-day trial periods in which they were alternatively and randomly fitted with two types of multifocal lenses. Habitual tasks were described in terms of observation distance, visual demand level and time allocation. Subjects graded visual satisfaction with each pair of lenses and each habitual task at different times during each trial. Overall satisfaction was evaluated after completion of the two trial periods. Wearing success was determined by the percentage of subjects opting to continue multifocal lens wear and by the number of subjects still wearing their lenses six months later. Results Viewing distance and visual demand level were found to influence visual satisfaction (p < 0.001). Visual satisfaction decreased for tasks involving higher visual demands and for near and far viewing distances, rather than for intermediate vision or a combination of near and far vision. A combined effect of lens type and evaluation time was discovered (p = 0.046). Although 78% of subjects decided to continue lens wear, only one subject was wearing them on a daily basis 6 months after the completion of the study. Insufficient quality of vision was reported as the main reason for multifocal contact lens discontinuation. Conclusions A task oriented visual satisfaction evaluation may prove helpful in lens design selection, as well as in predicting wearing success.

Different approaches of physical training used in the management of type 2 diabetes

Background Type 2 diabetes is now a common and serious global health problem, which, for most countries, has evolved in association with rapid cultural and social changes, ageing populations, increasing urbanisation, dietary changes, reduced physical activity and other unhealthy lifestyle and behavioural patterns. Aims To identify the different approaches to physical training used in the last decade in the management of type 2 diabetes. Methods We searched PubMed and Science Direct for all randomised clinical trials from 1999 to 30 May 2010. Results We selected 17 randomised controlled trials, five studies with aerobic exercise, five with resistance exercise and seven combined exercise studies. Conclusions The use of resistance training for the treatment of type 2 diabetes is becoming more commonly used in the management of type 2 diabetes. The number of studies using resistance exercise has been growing over the last decade, and has actually become as widely used as the popular aerobic exercise. In turn, most of the reviewed studies have used interventions combining resistance and aerobic exercise. An exercise programme for diabetic patients should be seen as a form of treatment. Hence, there were no established guidelines for the duration of the programme, because exercise should become a habitual daily task, and assumed in a new lifestyle for long-term glucose control.

An acoustic study of coarticulation in dysarthric speakers with Parkinson disease.

Anticipatory vowel coarticulation in obstruent + vowel syllables was studied for 9 dysarthric males with mild to moderate idiopathic Parkinson disease (PD) and a group of 10 healthy males. In addition to studying coarticulatory differences for speakers' habitual rate repetitions, a graded speaking rate task was used to investigate the effect of rate variation on coarticulation. The ratio of F2 onset frequency/F2 target frequency was used to infer coarticulation (i.e., ratios of 1.0 indicate complete vowel harmony at vowel onset, and ratios greater than 1.0 indicate relatively less coarticulation). Because F2 onset frequency is a relatively novel measure of coarticulation, a more common measure of anticipatory vowel coarticulation-fricative F2-was obtained for a subset of the speech stimuli and compared to F2 onset measures. Ratios of fricative F2/F2 target frequency also were computed to infer coarticulation and the results were compared to the F2 onset/F2 target ratios. The results indicated a modest relationship between F2 onset frequency and fricative F2 for both speaking tasks and speaker groups, with a stronger relationship for the graded rate task. Regression analyses for the graded rate task further indicated that longer vowel durations were associated with larger ratios for both speaker groups. Thus, coarticulation tended to increase with faster rates and decrease with slower rates, although the relationship was more systematic for control speakers. Ratios for the habitual task tended to be smaller for speakers with PD, suggesting increased coarticulation relative to control speakers. This effect was not entirely attributable to the more rapid speaking rates for speakers with PD. Because habitual rate F2 onset/F2 target ratios tended to underestimate the extent to which coarticulation was increased for speakers with PD-compared to the fricative F2/F2 target ratios-measures other than F2 onset should be used to infer absolute differences in extent of coarticulation for speakers with PD and healthy controls.