Multiple roles for time in short-term memory: evidence from serial recall of order and timing

Three experiments are reported that examine the relationship between short-term memory for time and order information, and the more specific claim that order memory is driven by a timing signal. Participants were presented with digits spaced irregularly in time and postcued (Experiments 1 and 2) or precued (Experiment 3) to recall the order or timing of the digits. The primary results of interest were as follows: (a) Instructing participants to group lists had similar effects on serial and timing recall in inducing a pause in recall between suggested groups; (b) the timing of recall was predicted by the timing of the input lists in both serial recall and timing recall; and (c) when the recall task was precued, there was a tendency for temporally isolated items to be more accurately recalled than temporally crowded items. The results place constraints on models of serial recall that assume a timing signal generates positional representations and suggest an additional role for information about individual durations in short-term memory.     

Timing during interruptions in timing

Duration and location of breaks in time interval production were manipulated in various conditions of stimulus presentation (Experiments 1-4). Produced intervals shortened and then stabilized as break duration lengthened, suggesting that participants used the break as a preparatory period to restart timing as quickly as possible at the end of the break. This interpretation was supported in Experiment 5, in which similar results were obtained with a reaction time response executed at the end of the break. In all experiments, produced intervals lengthened as the break occurred later during the interval. The authors conclude that varying break location and duration reveal, respectively, the influence of attentional time-sharing before the interruption and of preparatory processes taking place during the break.     

Paying Attention to Time as One Gets Older

Age-related changes in attention and interval timing as a function of time of day were examined using a temporal bisection task with single and compound auditory and visual stimuli. Half of the participants in each age group were tested in the morning, and half were tested in the afternoon. Duration judgments were found to be shorter for visual signals than for auditory signals. This discrepancy was greater in the morning than in the afternoon and larger for the older than for the younger adults. Young adults showed equal sensitivity to signal duration for single and compound trials and higher sensitivity in the afternoon than in the morning for both signal modalities. In contrast, older adults showed impaired sensitivity on compound trials and the greatest sensitivity overall to single visual trials in the morning. These results suggest that age-related reductions in attentional resources may cause older adults to focus on signals that require controlled attention during specific phases of the circadian cycle.     

Contrasting effects of interference and of breaks in interval timing

When a break is introduced during an interval to be timed, the interval is perceived shorter as break location is delayed. This is interpreted as a result of attention sharing between timing and monitoring the source of the break signal. Similar effects and interpretations are found in another context involving interfering tasks. Such tasks are assumed to induce transient interruptions in timing, comparable to those obtained with breaks. Break and interference conditions were contrasted in a temporal reproduction procedure with identical stimuli. Both conditions induced temporal underestimation and similar location effects. Similar trends occurred in a control condition where no processing of the interfering signal was required. The data suggest that expectancy, intentional processing, and automatic attraction of attention shorten temporal estimates.     

The effects of aging on time reproduction in delayed free-recall

The experiments presented here demonstrate that normal aging amplifies differences in time production occurring in delayed free-recall testing. Experiment 1 compared the time production ability of two healthy aged groups as well as college-aged participants. During the test session, which followed a 24-h delay and omitted all feedback and examples of the two target intervals, the two groups of aged participants' over-produced a 6s interval. This effect is similar in form to errors shown by young participants, but twice the magnitude. Productions of a 17 s interval were generally accurate overall. However, further analysis indicated that the majority of aged participants over-produced the 17 s interval while a minority greatly under-produced the 17 s interval. Furthermore, aged participants showed violations of the scalar property of timing variability in the training session, while in the test session, only those who under-produced the 17 s interval showed this tendency. In contrast, training session performance was good for all participants. Experiments 2 and 3 investigated the ability of the participants in Experiment 1 to reproduce the length of a line from memory, under conditions analogous to those of the time production experiments. These experiments provided tests of the specificity of the errors observed in Experiment 1. Performance in the older participants was accurate, if more variable, compared to the young participants, in contrast to the time production results, indicating that production inaccuracy in free-recall is specific to interval timing in the current context.     

The effect of Parkinson's disease on time estimation as a function of stimulus duration range and modality

The present research sought to investigate the role of the basal ganglia in timing of sub- and supra-second intervals via an examination of the ability of people with Parkinson's disease (PD) to make temporal judgments in two ranges, 100-500 ms, and 1-5 s. Eighteen non-demented medicated patients with PD were compared with 14 matched controls on a duration-bisection task in which participants were required to discriminate auditory and visual signal durations within each time range. Results showed that patients with PD exhibited more variable duration judgments across both signal modality and duration range than controls, although closer analyses confirmed a timing deficit in the longer duration range only. The findings presented here suggest the bisection procedure may be a useful tool in identifying timing impairments in PD and, more generally, reaffirm the hypothesised role of the basal ganglia in temporal perception at the level of the attentionally mediated internal clock as well as memory retrieval and/or decision-making processes.     

Adult Age Differences in Memory for Verbs and Nouns

Younger and older adults were asked to remember noun pairs (e.g., head – cap), verb pairs (e.g., bounce – throw), and verb-noun pairs (e.g., break – stick). For half of the pairs, participants used imagined objects and performed an action or series of related actions for each pair. For the other half of the pairs, participants read but did not perform the pairs. Free recall and cued recall tests revealed that age differences in memory for both performed and nonperformed items were larger for verbs than for nouns. The recall advantage of nouns over verbs was larger for older than for younger adults. Verbs are hypothesized to be more difficult for older adults to remember because they are more and less specific than nouns and because it is more difficult to integrate verbs with other words than to integrate nouns with other words.     

Chronic treatment with haloperidol induces deficits in working memory and feedback effects of interval timing

Normal participants (n=5) having no experience with antipsychotic drugs and medicated participants (n=5) with clinical experience with chronic low doses of haloperidol (3-10 mg/day for 2-4 months) in the treatment of neuroses were evaluated for the effects of inter-trial interval (ITI) feedback on a discrete-trials peak-interval timing procedure. Feedback was presented during the ITI in the form of a histogram showing the distribution of the responses participants made on the previous trial plotted on a relative time scale. As feedback concerning the accuracy and precision of a reproduced duration (e.g., 7- and 14-s visual signals) became more remote in time, reproduced intervals gradually lengthened in duration. This rightward horizontal shift in peak time increased as a function of the probability of feedback and was enhanced by chronic treatment with haloperidol in a manner that was proportional to the duration of the signal. Our data suggest a gradual change in the underlying representation of the signal duration as a function of the remoteness of ITI feedback that is dependent upon both changes in working memory and the speed of the internal clock used to time durations in the seconds-to-minutes range.     

Acquisition of decision making criteria: reward rate ultimately beats accuracy

Speed-accuracy trade-offs strongly influence the rate of reward that can be earned in many decision-making tasks. Previous reports suggest that human participants often adopt suboptimal speed-accuracy trade-offs in single session, two-alternative forced-choice tasks. We investigated whether humans acquired optimal speed-accuracy trade-offs when extensively trained with multiple signal qualities. When performance was characterized in terms of decision time and accuracy, our participants eventually performed nearly optimally in the case of higher signal qualities. Rather than adopting decision criteria that were individually optimal for each signal quality, participants adopted a single threshold that was nearly optimal for most signal qualities. However, setting a single threshold for different coherence conditions resulted in only negligible decrements in the maximum possible reward rate. Finally, we tested two hypotheses regarding the possible sources of suboptimal performance: (1) favoring accuracy over reward rate and (2) misestimating the reward rate due to timing uncertainty. Our findings provide support for both hypotheses, but also for the hypothesis that participants can learn to approach optimality. We find specifically that an accuracy bias dominates early performance, but diminishes greatly with practice. The residual discrepancy between optimal and observed performance can be explained by an adaptive response to uncertainty in time estimation.     

To count or not to count: the effect of instructions on expecting a break in timing

When a break is expected during a time interval production, longer intervals are produced as the break occurs later during the interval. This effect of break location was interpreted as a result of distraction related to break expectancy in previous studies. In the present study, the influence of target duration and of instructions about chronometric counting strategies on the break location effect was examined. Using a strategy such as chronometric counting enhances the reliability of temporal processing, typically in terms of reduced variability, and could influence how timing is affected by break expectancy, especially when relatively long target durations are used. In two experiments, results show that time productions lengthened with increasing value of break location at various target durations and that variability was greater in the no-counting than in the counting instruction condition. More important, the break location effect was stronger in the no-counting than in the counting instruction condition. We conclude that chronometric counting orients attention toward timing processes, making them less likely to be disrupted by concurrent nontemporal processes.     

Self control of when and how much to test face-name pairs in a novel spaced retrieval paradigm: An examination of age-related differences

ABSTRACT Although the mnemonic benefit of spaced retrieval is well established, the way in which participants naturally space their own retrieval is relatively unexplored. To examine this question, a novel experimental paradigm was developed in which young and healthy older adults were given control over the frequency and timing of retrieval practice in the context of an ongoing reading task. Results showed that both age groups naturally expanded the intervals of their retrieval practice. When instructed, younger adults but not older adults were better able to employ equal spaced retrieval during retrieval practice. However, even under equal spaced retrieval instructions, young adults included an early retrieval attempt prior to equally spacing their retrieval. Although memory performance was equivalent, secondary task performance was reduced in the experimenter-instructed condition compared with the participant-selected condition. The results overall indicate that both younger and older participants naturally monitor their memory and efficiently use testing to titrate the number and timing of retrieval attempts used during the acquisition phase.     

Age slowing down in detection and visual discrimination under varying presentation times

The reaction time has been described as a measure of perception, decision making, and other cognitive processes. The aim of this work is to examine age‐related changes in executive functions in terms of demand load under varying presentation times. Two tasks were employed where a signal detection and a discrimination task were performed by young and older university students. Furthermore, a characterization of the response time distribution by an ex‐Gaussian fit was carried out. The results indicated that the older participants were slower than the younger ones in signal detection and discrimination. Moreover, the differences between both processes for the older participants were higher, and they also showed a higher distribution average except for the lower and higher presentation time. The results suggest a general slowdown in both tasks for age under different presentation times, except for the cases where presentation times were lower and higher. Moreover, if these parameters are understood to be a reflection of executive functions, these findings are consistent with the common view that age‐related cognitive deficits show a decline in this function.     

Age and emotion affect how we look at a face: visual scan patterns differ for own-age versus other-age emotional faces

We investigated how age of faces and emotion expressed in faces affect young (n=30) and older (n=20) adults' visual inspection while viewing faces and judging their expressions. Overall, expression identification was better for young than older faces, suggesting that interpreting expressions in young faces is easier than in older faces, even for older participants. Moreover, there were age-group differences in misattributions of expressions, in that young participants were more likely to label disgusted faces as angry, whereas older adults were more likely to label angry faces as disgusted. In addition to effects of emotion expressed in faces, age of faces affected visual inspection of faces: Both young and older participants spent more time looking at own-age than other-age faces, with longer looking at own-age faces predicting better own-age expression identification. Thus, cues used in expression identification may shift as a function of emotion and age of faces, in interaction with age of participants.     

The Importance of On-going Concurrent Activities as a Function of Age in Time- and Event-based Prospective Memory

Time-based prospective memory is assumed to involve more self-initiated activities than event-based prospective memory. As age negatively affects self-initiated activities, older participants will show more prospectivememory deterioration than younger participants in time-based tasks. Einstein, McDaniel, Richardson, Guynn, and Cunfer (1995) indeed observed such a decrement in time-based prospective memory while d'Ydewalle, Utsi, and Brunfaut (1996) obtained a better time-based than event-based prospective memory among elderly. The on-going concurrent activity in Einstein et al. (1995) involved answering general questions, whereas d'Ydewalle et al. (1996) used a face-identification task. In an attempt to explain the discrepant results, the present experiment compares time- and event-based memory with young and older participants using the two types of on-going task. However, the better performance of the older participants in the timebased prospective memory task is obtained in the two on-going tasks. A difference in timing constraints in the procedure may explain why the older participants in Einstein et al. (1995) did perform more poorly in the timebased task, whereas our ageing participants did not show such a deterioration, suggesting that the slowing down of mental activities may provide a better explanation than the increasing lack of self-initiated activities by the elderly. All age effects in prospective-memory performance disappear when performance on the target items (i.e. items where a prospective-memory response is required) in the on-going task is taken into account. We emphasise the need to study trade-offs in prospective-memory research as a prospective-memory task is always embedded in another (on-going) activity.     

Evidence for Age-related Changes to Temporal Attention and Memory from the Choice Time Production Task

ABSTRACT

The effect of aging on interval timing was examined using a choice time production task, which required participants to choose a key response based on the location of the stimulus, but to delay responding until after a learned time interval. Experiment 1 varied attentional demands of the response choice portion of the task by varying difficulty of stimulus–response mapping. Choice difficulty affected temporal accuracy equally in both age groups, but older participants' response latencies were more variable under more difficult response choice conditions. Experiment 2 tested the contribution of long-term memory to differences in choice time production between age groups over 3 days of testing. Direction of errors in time production between the two age groups diverged over the 3 sessions, but variability did not differ. Results from each experiment separately show age-related changes to attention and memory in temporal processing using different measures and manipulations in the same task.     

The effects of expertise and age on rhythm production: adaptations to timing and sequencing constraints.

We investigate age- and expertise-related individual differences in component processes of rhythmic timing. To this end we apply analysis of covariance structure and symbolic dynamics to time series obtained from performances of two bimanual rhythm tasks at different tempos. Results show similar effects for peripheral motor implementation and timekeeper execution in young and older amateur pianists. Older participants show specific problems with temporal sequencing processes (specification of different target intervals). Expert pianists show lower variability in both motor implementation and timekeeper execution and they accommodate to the sequencing demands of different tempos by selectively relying on integrated or parallel timing. We argue that the observed timing control characteristics reflect individuals' adaptations to internal processing limitations and performance constraints.     

Effect of age and gender in the control of elbow flexion movements

In previous studies of rapid elbow movements in young healthy men, characteristic task-dependent changes in the patterns of muscle activation when movement speed or distance was varied have been reported. In the present study, the authors investigated whether age or gender is associated with changes in the patterns of muscle activity previously reported in young men. Arm movements of 10 healthy older and 10 healthy younger participants (5 men and 5 women in each group) were studied. Surface electromyograms (EMGs) from agonist (biceps) and antagonist (triceps) muscles, kinematic and kinetic parameters, as well as anthropometric and strength measures were recorded. All 4 groups of participants showed similar task- (distance or speed) dependent changes in biphasic EMG activity. Similar modulation of the initial rate of rise of the EMG, integrated agonist and antagonist EMG activity, as well as their relative timing were observed in all 4 groups. Those results suggest that older individuals of both genders retain the control strategies for elbow movements used by young individuals. Despite the qualitative similarities in the patterns of muscle activation, the men moved more quickly than the women, and younger participants moved more quickly than older participants. Those performance differences could not be explained in terms of differences in body size and strength alone.     

Effect of Age and Gender in the Control of Elbow Flexion Movements

In previous studies of rapid elbow movements in young healthy men, characteristic task-dependent changes in the patterns of muscle activation when movement speed or distance was varied have been reported. In the present study, the authors investigated whether age or gender is associated with changes in the patterns of muscle activity previously reported in young men. Arm movements of 10 healthy older and 10 healthy younger participants (5 men and 5 women in each group) were studied. Surface electromyograms (EMGs) from agonist (biceps) and antagonist (triceps) muscles, kinematic and kinetic parameters, as well as anthropometric and strength measures were recorded. All 4 groups of participants showed similar task- (distance or speed) dependent changes in biphasic EMG activity. Similar modulation of the initial rate of rise of the EMG, integrated agonist and antagonist EMG activity, as well as their relative timing were observed in all 4 groups. Those results suggest that older individuals of both genders retain the control strategies for elbow movements used by young individuals. Despite the qualitative similarities in the patterns of muscle activation, the men moved more quickly than the women, and younger participants moved more quickly than older participants. Those performance differences could not be explained in terms of differences in body size and strength alone.     

Expecting a break in time estimation: attentional time-sharing without concurrent processing

The interference from nontemporal processing on concurrent time estimation is usually attributed to disruption in timing caused by attentional requirements of nontemporal processing. Here, we examined interruption in timing without concurrent nontemporal processing. Empty breaks of various durations, during time-interval production, lengthened produced intervals. Moreover, an effect of break location was observed: Intervals lengthened proportionally to prebreak duration. When cued and uncued uninterrupted trials were introduced, the lengthening was proportional to the duration for which a break was expected. It was concluded that attentional time-sharing between time estimation and expectation of its interruption contributed to the interference effect in time-estimation research, independently of any concurrent processing requirements during time estimation.     

Age and emotion affect how we look at a face: Visual scan patterns differ for own-age versus other-age emotional faces

We investigated how age of faces and emotion expressed in faces affect young (n=30) and older (n=20) adults’ visual inspection while viewing faces and judging their expressions. Overall, expression identification was better for young than older faces, suggesting that interpreting expressions in young faces is easier than in older faces, even for older participants. Moreover, there were age-group differences in misattributions of expressions, in that young participants were more likely to label disgusted faces as angry, whereas older adults were more likely to label angry faces as disgusted. In addition to effects of emotion expressed in faces, age of faces affected visual inspection of faces: Both young and older participants spent more time looking at own-age than other-age faces, with longer looking at own-age faces predicting better own-age expression identification. Thus, cues used in expression identification may shift as a function of emotion and age of faces, in interaction with age of participants.