Time, trace, memory

Objections to a trace hypothesis for interval timing do not apply to the multiple-time-scale (MTS) theory, which incorporates a dynamic trace tuned by the system history and can easily accommodate interval timing over a 1,000:1 range. The MTS model can also account for Weber's law as well as systematic deviations from it. Contrary to our critics, we contend that patterns of variance in interval timing experiments are not fully described by scalar expectancy theory, and that attempting to understand timing by assigning variance to different elements of a flexible model that lacks inductive support is a flawed strategy, because the attempt may be successful even if the model is wrong. We further argue that biological plausibility is an unreliable guide to the development of behavioral theory, that prediction is not the same as test, that induction should precede deduction, and that a rat is not a clock.     

Timing the second response in two-response avoidance.

Rats were trained on a free-operant avoidance task requiring two lever presses within R seconds, with the opportunity for each response distinguished by differing stimuli. Response latencies at a variety of response-shock intervals were found to be proportional to the time available for the response. These results are shown to be consonant with a scalar expectancy model of timing behavior.     

Evaluation of quantitative theories of timing

Scalar timing theory is a clear, complete, modular, and precise theory of timing that explains much of the data from many timing procedures, but not all of the data from all of the procedures. The multiple-time-scale theory of timing provides an alternative representation of time that has not yet been tested with respect to its fit to timing data.     

Concurrent schedules: a quantitative relation between changeover behavior and its consequences

Data from several published experiments on concurrent variable-interval schedules were analyzed with respect to the effects of changeover delay on the time spent responding on a schedule before changing to an alternate schedule: i.e., the interchangeover time. Interchangeover time increases as the duration of the changeover delay increases, and the present analysis shows that a power function describes the relation. The power relation applied in spite of numerous differences in the experiments: different variable-interval schedules for the concurrent pairs; equal or unequal reinforcement rates for the schedules of the concurrent pairs; different durations of the changeover delay; response-dependent or response-independent reinforcers; pigeons or rats as subjects; different reinforcers. A power function also described the data in experiments where the changeover incurred a timeout, where a fixed ratio was required to changeover, and also when asymmetrical changeover delays were used.     

Effects of signaling on temporal control of behavior in response‐initiated fixed intervals

Behavior and events distributed in time can serve as markers that signal delays to future events. The majority of timing research has focused on how behavior changes as the time to some event, usually food availability, decreases. The primary objective of the two experiments presented here was to assess how behavior changes as time passes between two time markers when the first time marker was manipulated but the second, food delivery, was held constant. Pigeons were exposed to fixed‐interval, response‐initiated fixed‐interval, and signaled response‐initiated fixed‐interval 15‐ and 30‐s schedules of reinforcement. In Experiment 1, first‐response latencies were systematically shorter in the signaled response‐initiated schedules than response‐initiated schedules, suggesting that the first response was a more effective time marker when it was signaled. In Experiment 2, responding in no‐food (i.e. “peak”) trials indicated that timing accuracy was equivalent in the three schedule types. Compared to fixed interval schedules, timing precision was reduced in the signaled response‐initiated schedules and was lowest in response‐initiated schedules. Results from Experiments 1 and 2 coupled with previous research suggest that the overall “informativeness” of a time marker relative to other events and behaviors in the environment may determine its efficacy.     

Step changes in the intertrial interval in the midsession reversal task: Predicting pigeons' performance with the learning-to-time model

Our goal was to assess the role of timing in pigeons' performance in the midsession reversal task. In discrete-trial sessions, pigeons learned to discriminate between 2 stimuli, S1 and S2. Choices of S1 were reinforced only in the first half of the session and choices of S2 were reinforced only in the second half. Typically, pigeons choose S2 before the contingency reverses (anticipatory errors) and S1 after (perseverative errors), suggesting that they time the interval from the beginning of the session to the contingency reversal. To test this hypothesis, we exposed pigeons to a midsession reversal task and, depending on the group, either increased or decreased the ITI duration. We then contrasted the pigeons' performance with the predictions of the Learning-to-Time (LeT) model: In both conditions, preference was expected to reverse at the same time as in the previous sessions. When the ITI was doubled, pigeons' preference reversal occurred at half the trial number but at the same time as in the previous sessions. When the ITI was halved, pigeons' preference reversal occurred at a later trial but at an earlier time than in the previous sessions. Hence, pigeons' performance was only partially consistent with the predictions of LeT, suggesting that besides timing, other sources of control, such as the outcome of previous trials, seem to influence choice.     

短时距标量计时模型的建构研究

采用预期式研究范式,创造性地使用单任务研究程序,从心理物理学的视角,通过六个实验系统地考查了影响被试短时距(6s至24s)估计的标量特性和物理、心理和生理的信息源因素.深入探讨了注意、激活、间断和间断期望效应因素对时间估计行为的影响及时序信息的动态加工过程.在此基础上,包含时钟、累加、记忆和比较四个动态加工过程的短时距标量计时模型得以建构.     

A Turing Test for Computational and Associative Theories of Learning

A Turing test is proposed to evaluate current computational and associative models of learning, and to guide theoretical developments. This test requires a specification of the procedures to which the model applies, a sampling of procedures and response measures, and an objective way to determine the difficulty of discriminating the responses of the model from the responses of the animal. Scalar timing theory is used as an example of a well-developed computational theory of timing that involves addition, multiplication, division, and sampling. The behavioral theory of timing is used as an example of a well-developed associative theory of timing that involves state transitions and strengthening of connections. A Turing test provides a way to evaluate such theories.     

Performances on ratio and interval schedules of reinforcement: Data and theory

Two differences between ratio and interval performance are well known: (a) Higher rates occur on ratio schedules, and (b) ratio schedules are unable to maintain responding at low rates of reinforcement (ratio “strain”). A third phenomenon, a downturn in response rate at the highest rates of reinforcement, is well documented for ratio schedules and is predicted for interval schedules. Pigeons were exposed to multiple variable-ratio variable-interval schedules in which the intervals generated in the variable-ratio component were programmed in the variable-interval component, thereby “yoking” or approximately matching reinforcement in the two components. The full range of ratio performances was studied, from strained to continuous reinforcement. In addition to the expected phenomena, a new phenomenon was observed: an upturn in variable-interval response rate in the midrange of rates of reinforcement that brought response rates on the two schedules to equality before the downturn at the highest rates of reinforcement. When the average response rate was corrected by eliminating pausing after reinforcement, the downturn in response rate vanished, leaving a strictly monotonic performance curve. This apparent functional independence of the postreinforcement pause and the qualitative shift in response implied by the upturn in variable-interval response rate suggest that theoretical accounts will require thinking of behavior as partitioned among at least three categories, and probably four: postreinforcement activity, other unprogrammed activity, ratio-typical operant behavior, and interval-typical operant behavior.     

Time and memory: towards a pacemaker-free theory of interval timing

A popular view of interval timing in animals is that it is driven by a discrete pacemaker-accumulator mechanism that yields a linear scale for encoded time. But these mechanisms are fundamentally at odds with the Weber law property of interval timing, and experiments that support linear encoded time can be interpreted in other ways. We argue that the dominant pacemaker-accumulator theory, scalar expectancy theory (SET), fails to explain some basic properties of operant behavior on interval-timing procedures and can only accommodate a number of discrepancies by modifications and elaborations that raise questions about the entire theory. We propose an alternative that is based on principles of memory dynamics derived from the multiple-time-scale (MTS) model of habituation. The MTS timing model can account for data from a wide variety of time-related experiments: proportional and Weber law temporal discrimination, transient as well as persistent effects of reinforcement omission and reinforcement magnitude, bisection, the discrimination of relative as well as absolute duration, and the choose-short effect and its analogue in number-discrimination experiments. Resemblances between timing and counting are an automatic consequence of the model. We also argue that the transient and persistent effects of drugs on time estimates can be interpreted as well within MTS theory as in SET. Recent real-time physiological data conform in surprising detail to the assumptions of the MTS habituation model. Comparisons between the two views suggest a number of novel experiments.     

Duration comparison: relative stimulus differences stimulus age, and stimulus predictiveness.

Under a psychophysical trials procedure, pigeons were presented with a red light of one duration followed by a green light of a second duration. Eight geometrically spaced base durations were paired with one of four shorter and four longer durations as the alternate member of a duration pair, with different pairs randomly intermixed. One choice was reinforced if red had lasted longer than green, and a second choice was reinforced if green had lasted longer. Performance was compared when all the base durations and their pair members were included (entire-range condition) or when only the four longest base durations and their comparison durations (restricted-range condition) were used. Discrimination sensitivity decreased for longer duration pairs under both conditions, supporting a memory-based account. Sensitivity was lower under the restricted-range condition. Under both conditions, a bias to report "green as longer" increased as the second green duration increased. Bias changed as a matching function of the green-duration predictiveness of the correct choice. The results are related to a quantitative model of timing and remembering proposed by Staddon.     

The effects of morphine on the production and discrimination of interresponse times

Recent experiments suggest that the effects of drugs of abuse on the discrimination of the passage of time may differ for experimenter-imposed and subject-produced events. The current experiment examined this suggestion by determining the effects of morphine on the discrimination of interresponse times (IRTs). Pigeons pecked a center key on a random-interval 20-s schedule of matching-to-sample trials. Once the interval had timed out, a choice trial randomly followed either a short (2- to 3-s) or long (6- to 9-s) IRT on the center key. Pecking the side key lit one color produced food after a short IRT, and pecking the side key lit the other color produced food after a long IRT. Two experimental phases differed in the functional role of the different key colors. Under control conditions, the IRT distributions had two modes, one at the lower bound of the short category and a smaller one at the lower bound of the long category. Pigeons accurately categorized the duration of the IRTs: One key color was pecked following short IRTs and the other key color was pecked following long IRTs. Morphine flattened the IRT distribution and reduced the accuracy of categorizing IRTs. Categorization of long IRTs was particularly disrupted. Morphine did not produce overestimation of time as assessed by the production or categorization of IRTs. These results are similar to those obtained previously for the effects of morphine on the discrimination of the duration of experimenter-imposed events.     

Sensory superstition on multiple interval schedules.

Pigeons were exposed to multiple schedules in which an irregular repeating sequence of five stimulus components was correlated with the same reinforcement schedule throughout. Stable, idiosyncratic, response-rate differences developed across components. Components were rank-ordered by response rate; an approximately linear relation was found between rank order and the deviation of mean response rate from the overall mean rate. Nonzero slopes of this line were found for multiple fixed-interval and variable-time schedules and for multiple variable-interval schedules both when number of reinforcements was the same in all components and when it varied. The steepest function slopes were found in the variable schedules with relatively long interfood intervals and relatively short component durations. When just one stimulus was correlated with all components of a multiple variable-interval schedule, the slope of the line was close to zero. The results suggest that food-rate differences may be induced initially by different reactions to the stimuli and subsequently maintained by food.     

Species differences in temporal control of behavior

Temporal control of rats' and pigeons' responding was analyzed and compared in detail on fixed-interval and fixed-time schedules with parameters of 30, 60, and 120 seconds. On fixed-time schedules, rats' responding decreased greatly or ceased, whereas pigeons continued to respond, especially on low schedule values. The running rate of responses (calculated by excluding the postreinforcement pause) was related to the duration of the preceding postreinforcement pause for rats but not for pigeons. Changes in response rate in successive segments of the interval were best described by normal curves. The relationship between midpoints of the normal curves and schedule value was a power function, with an exponent of less than one for pigeons but greater than one for rats. These differences could be explained in terms of a basic difference between the key-peck and lever-press responses, the two being differently affected by the response-eliciting properties of food.     

Residence time in concurrent foraging with fixed times to prey arrival

Five pigeons were trained in a concurrent foraging procedure in which reinforcers were occasionally available after fixed times in two discriminated patches. In Part 1 of the experiment, the fixed times summed to 10 s, and were individually varied between 1 and 9 s over five conditions, with the probability of a reinforcer being delivered at the fixed times always .5. In Part 2, both fixed times were 5 s, and the probabilities of food delivery were varied over conditions, always summing to 1.0. In Parts 3 and 4, one fixed time was kept constant (Part 3, 3 s; Part 4, 7 s) while the other fixed time was varied from 1 s to 15 s. Median residence times in both patches increased with increases in the food-arrival times in either patch, but increased considerably more strongly in the patch in which the arrival time was increased. However, when arrival times were very different in the two patches, residence time in the longer arrival-time patch often decreased. Patch residence also increased with increasing probability of reinforcement, but again tended to fall when one probability was much larger than the other. A detailed analysis of residence times showed that these comprised two distributions, one around a shorter mode that remained constant with changes in arrival times, and one around a longer mode that monotonically increased with increasing arrival time. The frequency of shorter residence times appeared to be controlled by the probability of, and arrival time of, reinforcers in the alternative patch. The frequency of longer residence times was controlled directly by the arrival time of reinforcers in a patch, but not by the probability of reinforcers in a patch. The environmental variables that control both staying in a patch and exiting from a patch need to be understood in the study both of timing processes and of foraging.     

Interresponse-time sensitivity during discrete-trial and free-operant concurrent variable-interval schedules

Two experiments investigated the sensitivity of pigeons' choice to elapsed time since the last response (i.e., to inter-response time [IRT]) during concurrent variable-interval variable-interval schedules. Experiment 1 used a two-key discrete-trial procedure with variable intertrial intervals. Experiment 2 employed a three-key free-operant procedure. In both experiments choice was found to be a function of the active-schedule IRT, defined as the time since the most recent response. Monte Carlo simulations show how this finding permits the joining of several seemingly incompatible data sets held to both support and contradict a kind of choice strategy, termed momentary maximizing, which attempts to maximize momentary reinforcement probabilities. The studies suggest that only two variables are needed to describe the static molecular structure of concurrent variable-interval choice: active-schedule IRTs and "response states" consisting of the last one or two schedule choices.     

时间复制任务中的计时中断效应

以计时中断范式和时间复制任务相结合,考察了时间复制任务中是否存在计时中断效应。结果表明：（1）计时中断范式中1700ms和2300ms时距复制均出现高估现象,说明两种时距均低于相邻的高低估现象的转换点;（2）计时中断范式中1700ms和2300ms的时距复制任务没有支持计时标量特性;（3）计时中断范式中1700ms和2300ms的时间复制任务出现了计时中断效应。     

时距估计中的重复刺激效应

Treisman及其同事最早发现人类对时距的判断很容易受到重复刺激的影响而发生扭曲或偏离,并认为时距估计中的重复刺激具有两种效应。着重介绍了时距估计中重复刺激效应产生的机制及其理论模型、重复刺激效应的影响因素。提出了时距估计中重复刺激效应未来研究中值得关注的几个主要问题。