标量计时模型的影响因素及发展

标量计时模型为人类时间知觉的研究提供了理论框架和研究范式, 它采用信息加工的观点, 包含时钟、记忆和决策三个阶段。时间二分任务是在标量计时模型的框架下研究时间知觉和加工的理想范式。它要求被试对时距进行与标量计时模型相对应的多阶段操作, 包含了时间知觉所涉及的各个过程, 能有效测量主观时距和时间敏感性的变化。通过这个范式, 研究者发现, 除了任务参数, 年龄和疾病都会影响人的主观时距和/或时间敏感性。这些时间二分任务的实验结果促进了标量计时模型的发展, 最近提出的两阶段决策模型和差别模型分别以不同的方式对标量计时模型进行了修正, 并解释了参数设置的影响和计时的个体差异。     

Perceptual complexity,rather than valence or arousal accounts for distracter-induced overproductions of temporal durations

For humans and other species, the ability to estimate the physical passage of time is of fundamental importance for perceptual, cognitive or motor functions. Despite this importance, any subjective estimation of temporal durations not only depends on the temporal dynamics of the to-be-timed stimulus or event, but also can be distorted by non-temporal perceptual, cognitive, and emotional effects. This study aimed to further explore critical stimulus characteristics modulating distracter-induced distortions in human time-reproduction. To this end, we investigated whether subjectively rated distracter dimensions of arousal and valence (related to levels of emotionality), or rather stimulus complexity, as a confounder, produce distortions in participants' reproduction of a previously trained target interval. Accuracy and precision of time-reproduction have been measured in distracter-trials, and compared to timing performance in baseline-trials without any distraction. Results showed temporal overproductions in a magnitude of less than distracter duration only for complex distracters. Most importantly, arousal level and valence of distracters were not accountable for temporal distortions. Within an internal clock framework, our pattern of results can best be interpreted in the context of attention-, rather than arousal-based mechanisms of timing.     

Temporal order in memory and interval timing: an interference analysis

The effect of varying load in memory tasks performed during a time interval production was examined. In a first experiment, increasing load in memory search for temporal order affected concurrent time production more strongly than varying load in a spatial memory task of equivalent difficulty. This result suggests that timing uses some specific resources also required in processing temporal order in memory, resources that would not be used in the spatial memory task. A second experiment showed that the interference between time production and memory search involving temporal order was stronger when, during the timing task, a decision was made on the temporal position of a memory item, than when information on temporal order was retained throughout the interval to be produced. These results underscore the importance of considering the specific resources and processes involved when the interference between timing and concurrent non-temporal tasks is analyzed.     

Timing in a dual-task in children and adults: when the interference effect is higher with concurrent non-temporal than temporal information

This study used a dual task with participants of different levels of cognitive capacities, assessed with neuropsychological tests, to examine the attentional cost on time judgment of processing concurrent temporal and non-temporal information. Children and adults performed a temporal reproduction task with either an interfering temporal or non-temporal discrimination task. The results showed an underestimation of time in the dual task compared to the single task, the extent of which was directly linked to individual attentional capacities. However, the non-temporal task interfered more than the temporal task on the reproduced durations. Nonetheless, the temporal reproduction task equally affected performance in the non-temporal and the temporal discrimination task. These results reveal the predominant role of the cost of dual-tasking in interference effects on time judgment, and the lesser role of concurrent information, especially of temporal information. This suggests a lack of competition for attentional resources in the processing of multiple durations.     

Changing Sensitivity to Duration in Human Scalar Timing: An Experiment, a Review, and Some Possible Explanations

Evidence from a number of studies of human timing, using temporal generalization and bisection tasks, suggests more sensitive behavioural adjustment to presented durations under conditions in which the timing task demands discriminations between more closely spaced stimuli. An experiment using temporal generalization demonstrated this effect, as discrimination between a 600-msec standard duration and non-standard stimuli both shorter and longer than 600 msec was better when non-standard stimuli were more closely spaced around 600 msec. A review showed similar effects in other temporal generalization tasks and in a number of bisection studies, where time discrimination improved as the ratio of the long and short standards on the bisection task decreased. A standard model of human temporal generalization explained the experimental data in terms of a decrease in the response threshold under more difficult conditions, rather than changes in the representation of the standard duration. On the other hand, data from bisection could be modelled by assuming the contrary; that representations of the short and long standards of the task were more precise under the more difficult conditions. Explanations of some of these effects in terms of attention to duration and/or arousal-induced changes in the speed of an internal clock were discussed.     

I can time with a little help from my friends: effect of social enrichment on timing processes in Pigeons (<Emphasis Type="Italic">Columba livia</Emphasis>)

There is evidence that impulsive decision-making is associated with errors in timing. However, there has been little attempt to identify the putative mechanism responsible for impulsive animals’ timing errors. One means of manipulating impulsivity in non-human animals is providing different levels of access to conspecifics. These preclinical models have revealed that social isolation increases impulsive responding across a wide range of tasks. The goal of the present study was to determine whether social isolation modulates time perception in pigeons by inducing more variability or a bias to underestimate the passage of time in temporal judgments. A temporal bisection task was used to characterize time perception. One group of pigeons performed the bisection following social enrichment, and the remaining half of the pigeons were tested following social isolation. Results revealed pigeons in the social isolation condition categorized a temporal stimulus sample as “long” at shorter durations than pigeons in the social enrichment condition. These data highlight the mechanism(s) thought to underlie timing-based interventions aimed at reducing impulsivity in humans. Future work should consider whether impulsivity is produced by misperceptions of time or a reduced threshold for a response.     

Temporal Bisection in Humans with Longer Stimulus Durations

Normal adults were tested in eight temporal bisection conditions, using 500-Hz tones as stimuli. Stimulus lengths matched, or overlapped with, durations normally used in bisection experiments with animals, and chronometric counting was prevented by using a concurrent digit-shadowing task. Four experimental groups were used to investigate any effects of stimulus spacing, and stimuli were logarithmically or linearly spaced between standard 'short' and 'long' durations of 1 and 4, or 2 and 8 sec. A slight leftward shift of the psychophysical function was found in the logarithmic spacing condition, relative to linear spacing. Four other groups tested the conjecture that the ratio of the short and long standards might play some role in determining the location of the bisection point, and conditions with long/short ratios of 2: 1 and 5: 1 were used. In all cases the bisection point was close to the arithmetic mean of the short and long standards, rather than the geometric mean, as in animal studies. Overall, however, smaller long/short ratios (which may indicate more difficult temporal discriminations) produced more sensitive timing. When the long/short ratio was held constant, however, data showed nearly perfect superimposition, indicating conformity to scalar timing. In general, results were similar to those from experiments with humans that used much shorter durations, indicating the animal/human differences in bisection do not depend on the absolute lengths of the stimuli used.     

Females in the forefront: time-based intervention effects on impulsive choice and interval timing in female rats

Impulsive choice has been implicated in substance abuse, gambling, obesity, and other maladaptive behaviors. Deficits in interval timing may increase impulsive choices, and therefore, could serve as an avenue through which suboptimal impulsive choices can be moderated. Temporal interventions have successfully attenuated impulsive choices in male rats, but the efficacy of a temporal intervention has yet to be assessed in female rats. As such, this experiment examined timing and choice behavior in female rats, and evaluated the ability of a temporal intervention to mitigate impulsive choice behavior. The temporal intervention administered in this study was successful in reducing impulsive choices compared to a control group. Results of a temporal bisection task indicated that the temporal intervention increased long responses at the shorter durations. Further, results from the peak trials within the choice task combined with the progressive interval task suggest that the intervention increased sensitivity to delay and enhanced timing confidence. Overall, these results indicate that a temporal intervention can be a successful avenue for reducing impulsive choice behavior in female rats, and could contribute to the development of behavioral interventions to prevent impulsive choice and maladaptive behaviors that can be applied to both sexes.     

Comparing perceptual and preferential decision making

Perceptual and preferential decision making have been studied largely in isolation. Perceptual decisions are considered to be at a non–deliberative cognitive level and have an outside criterion that defines the quality of decisions. Preferential decisions are considered to be at a higher cognitive level and the quality of decisions depend on the decision maker’s subjective goals. Besides these crucial differences, both types of decisions also have in common that uncertain information about the choice situation has to be processed before a decision can be made. The present work aims to acknowledge the commonalities of both types of decision making to lay bare the crucial differences. For this aim we examine perceptual and preferential decisions with a novel choice paradigm that uses the identical stimulus material for both types of decisions. This paradigm allows us to model the decisions and response times of both types of decisions with the same sequential sampling model, the drift diffusion model. The results illustrate that the different incentive structure in both types of tasks changes people’s behavior so that they process information more efficiently and respond more cautiously in the perceptual as compared to the preferential task. These findings set out a perspective for further integration of perceptual and preferential decision making in a single ramework.     

Animal timing: a synthetic approach

Inspired by Spence’s seminal work on transposition, we propose a synthetic approach to understanding the temporal control of operant behavior. The approach takes as primitives the temporal generalization gradients obtained in prototypical concurrent and retrospective timing tasks and then combines them to synthetize more complex temporal performances. The approach is instantiated by the learning-to-time (LeT) model. The article is divided into three parts. In the first part, we review the basic findings concerning the generalization gradients observed in fixed-interval schedules, the peak procedure, and the temporal generalization procedure and then describe how LeT explains them. In the second part, we use LeT to derive by gradient combination the typical performances observed in mixed fixed-interval schedules, the free-operant psychophysical procedure, the temporal bisection task, and the double temporal bisection task. We also show how the model plays the role of a useful null hypothesis to examine whether temporal control in the bisection task is relative or absolute. In the third part, we identify a set of issues that must be solved to advance our understanding of temporal control, including the shape of the generalization gradients outside the range of trained stimulus durations, the nature of temporal memories, the influence of context on temporal learning, whether temporal control can be inhibitory, and whether temporal control is also relational. These issues attest to the heuristic value of a Spencean approach to temporal control.     

Postreinforcement signal processing

Postreinforcement signal processing by rats was demonstrated in six experiments that used a discrete-trials choice procedure. Experiment 1 assessed the extent to which rats are able to transfer knowledge about associations between postreinforcement signal durations and choice responses to conditions where a particular signal duration preceded the opportunity to make a choice response. In Experiment 2 the generality of the transfer effect was demonstrated by using both signal duration and signal modality as relevant stimulus attributes for the postreinforcement signals. The role of the relative durations of the reinforcement-signal gap and the intertrial interval was investigated in Experiment 3. In order to assess the effects of within-trial and between-trial signal relations on the acquisition of a temporal discrimination, both pre-and postreinforcement signals were presented on each trial in Experiments 4 and 5. The effects of pre- and postreinforcement signal relations on the steady-state performance of a temporal bisection task across three different signal ranges were studied in Experiment 6. The conclusion is that rats readily process various stimulus attributes of postreinforcement signals and that relations between postreinforcement signals, choice responses, and prereinforcement signals are major determinants of choice behavior.     

Comparison of perceptual and motor latencies via anticipatory and reactive response times

To compare the timing of perceptual and motor decisions, distinct tasks have been designed, all of which have yielded systematic differences between these two moments. These observations have been taken as evidence of a sensorimotor dissociation. Inasmuch as the distinction between perceptual and motor decision moments is conceptually warranted, this conclusion remains debatable, since the observed differences may reflect the dissimilarity between the stimulations/tasks used to assess them. Here, we minimize such dissimilarities by comparing response time (RT) and anticipatory RT (ART), an alternative technique with which to infer the relative perceptual decision moments. Observers pressed a key either in synchrony with the third of a sequence of three stimuli appearing at a constant pace (ART) or in response to the onset of this third stimulus presented at a random interval after the second (RT). Hence, the two stimulation sequences were virtually identical. Both the mean and the variance of RT were affected by stimulus intensity about 1.5 times more than were the mean and the variance of ART. Within the framework of two simple integration-to-bound models, these findings are compatible with the hypothesis that perceptual and motor decisions operate on the same internal signal but are based on distinct criteria, with the perceptual criterion lower than the motor one.     

Scalar properties in animal timing: conformity and violations

The article reviews data from animal subjects on a range of timing tasks (including fixed-interval and temporal differentiation schedules, stimulus timing, aversive conditioning, and Pavlovian methods) with respect to conformity to the two scalar properties of timing behaviour: mean accuracy and scalar (Weberian) variance. Systematic deviations were found in data from temporal differentiation schedules, timing of very short (<100 ms) or very long (>100 s) durations, effects of "task difficulty", and some special cases where circadian and interval timing seemed to interact, or where some specific durations seemed to be timed more precisely than others. Theoretical reconciliation of some of these deviations with underlying scalar timing can be achieved, but a number of problematical cases remain unexplained.     

Temporal expectation and information processing: a model-based analysis

People are able to use temporal cues to anticipate the timing of an event, enabling them to process that event more efficiently. We conducted two experiments, using the fixed-foreperiod paradigm (Experiment 1) and the temporal-cueing paradigm (Experiment 2), to assess which components of information processing are speeded when subjects use such temporal cues to predict the onset of a target stimulus. We analyzed the observed temporal expectation effects on task performance using sequential-sampling models of decision making: the Ratcliff diffusion model and the shifted-Wald model. The results from the two experiments were consistent: temporal expectation affected the duration of nondecision processes (target encoding and/or response preparation) but had little effect on the two main components of the decision process: response-threshold setting and the rate of evidence accumulation. Our findings provide novel evidence about the psychological processes underlying temporal-expectation effects on reaction time.     

Identification and bisection of temporal durations and tone frequencies: common models for temporal and nontemporal stimuli

Two experiments examined identification and bisection of tones varying in temporal duration (Experiment 1) or frequency (Experiment 2). Absolute identification of both durations and frequencies was influenced by prior stimuli and by stimulus distribution. Stimulus distribution influenced bisection for both stimulus types consistently, with more positively skewed distributions producing lower bisection points. The effect of distribution was greater when the ratio of the largest to smallest stimulus magnitude was greater. A simple mathematical model, temporal range frequency theory, was applied. It is concluded that (a) similar principles describe identification of temporal durations and other stimulus dimensions and (b) temporal bisection point shifts can be understood in terms of psychophysical principles independently developed in nontemporal domains, such as A. Parducci's (1965) range frequency theory.     

Human performance on the temporal bisection task

The perception and processing of temporal information are tasks the brain must continuously perform. These include measuring the duration of stimuli, storing duration information in memory, recalling such memories, and comparing two durations. How the brain accomplishes these tasks, however, is still open for debate. The temporal bisection task, which requires subjects to compare temporal stimuli to durations held in memory, is perfectly suited to address these questions. Here we perform a meta-analysis of human performance on the temporal bisection task collected from 148 experiments spread across 18 independent studies. With this expanded data set we are able to show that human performance on this task contains a number of significant peculiarities, which in total no single model yet proposed has been able to explain. Here we present a simple 2-step decision model that is capable of explaining all the idiosyncrasies seen in the data.     

Alerting attention and time perception in children

This experiment investigated the effect of a signal (i.e., a click) warning of the arrival of a stimulus to be timed on temporal discrimination in children aged 3, 5, and 8 years (N=86), using a bisection task with visual stimuli ranging from 0.5 to 2s or 1 to 4s. In all groups, the psychophysical functions were orderly with the proportion of long responses increasing with the stimulus duration, although the steepness of functions increased with age. Stimulus durations were judged to be longer with than without the click in all age groups. With the click, time sensitivity also improved and more particularly in the younger children. The statistical results suggest, within the framework of the scalar timing theory, that the click reduces the closing latency of the switch that connects the pacemaker to the accumulator in the internal clock and also reduces its trial-by-trial variability.     

Scalar properties in animal timing: Conformity and violations

The article reviews data from animal subjects on a range of timing tasks (including fixed-interval and temporal differentiation schedules, stimulus timing, aversive conditioning, and Pavlovian methods) with respect to conformity to the two scalar properties of timing behaviour: mean accuracy and scalar (Weberian) variance. Systematic deviations were found in data from temporal differentiation schedules, timing of very short (<100 ms) or very long (>100 s) durations, effects of “task difficulty”, and some special cases where circadian and interval timing seemed to interact, or where some specific durations seemed to be timed more precisely than others. Theoretical reconciliation of some of these deviations with underlying scalar timing can be achieved, but a number of problematical cases remain unexplained.     

Ageing and temporal processing of durations within the psychological present

The predominant use of temporal information in everyday life concerns behaviour within the psychological present, which is said to have an upper limit of approximately 3–5 s. The present study was designed to investigate age differences in processing of temporal information within the psychological present by applying three distinct psychophysical tasks with base durations of 1 s. Forty young (mean age: 21.6 years) and forty older adults (mean age: 70.4 years) were presented with a temporal discrimination task, a temporal reproduction task, and a repeated production task. Pronounced impairment in older adults, as compared to young adults, was found for temporal discriminations. When asked to reproduce a 1-s target interval, young adults under-reproduced and older adults over-reproduced the target duration, but did not differ in overall accuracy and intra-individual variability. Repeated productions of a 1-s interval were unaffected by age. These findings are consistent with the notion that older adults show impaired performance when stimulus timing is required, whereas response timing is unaffected by ageing.     

The speed and accuracy of perceptual decisions in a random-tone pitch task

Research in perceptual decision making is dominated by paradigms that tap the visual system, such as the random-dot motion (RDM) paradigm. In this study, we investigated whether the behavioral signature of perceptual decisions in the auditory domain is similar to those observed in the visual domain. We developed an auditory version of the RDM task, in which tones correspond to dots and pitch corresponds to motion (the random-tone pitch task, RTP). In this task, participants have to decide quickly whether the pitch of a “sound cloud” of tones is moving up or down. Stimulus strength and speed–accuracy trade-off were manipulated. To describe the relationship between stimulus strength and performance, we fitted the proportional-rate diffusion model to the data. The results showed a close coupling between stimulus strength and the speed and accuracy of perceptual decisions in both tasks. Additionally, we fitted the full drift diffusion model (DDM) to the data and showed that three of the four participants had similar speed–accuracy trade-offs in both tasks. However, for the RTP task, drift rates were larger and nondecision times slower, suggesting that some DDM parameters might be dependent on stimulus modality (drift rate and nondecision time), whereas others might not be (decision bound). The results illustrate that the RTP task is suitable for investigating the dynamics of auditory perceptual choices. Future studies using the task might help to investigate modality-specific effects on decision making at both the behavioral and neuronal levels.