Verbal estimation of the magnitude of time, number, and length.

Performance similarities on tasks requiring the processing of different domains of magnitude (e.g. time, numerosity, and length) have led to the suggestion that humans possess a common processing system for all domains of magnitude (Bueti and Walsh in Philos Trans R Soc B 364:1831-1840, 2009). In light of this, the current study examined whether Wearden's (Timing Time Percept 3:223-245, 2015) model of the verbal estimation of duration could be applied to verbal estimates of numerosity and length. Students (n = 23) verbally estimated the duration, number, or physical length of items presented in visual displays. Analysis of the mean verbal estimates indicated the data were typical of that found in other studies. Analysis of the frequency of individual verbal estimates produced suggested that the verbal responses were highly quantized for duration and length: that is, only a small number of estimates were used. Responses were also quantized for number but to a lesser degree. The data were modelled using Wearden's (2015) account of verbal estimation performance, which simulates quantization effects, and good fits could be obtained providing that stimulus durations were scaled as proportions (0.75, 1.06, and 0.92 for duration, number, and length, respectively) of their real magnitudes. The results suggest that despite previous reports of similarities in the processing of magnitude, there appear to be differences in the way in which the underlying representations of the magnitudes are scaled and then transformed into verbal outputs.

Passage of time judgements.

The article discusses passage of time judgements (POTJs), judgements about how fast time seems to pass in some situation or during some event. It is argued that POTJs should be distinguished from duration judgements, and that the relation between the two remains to be identified. The article discusses (a) POTJs in laboratory situations and in the real world, (b) "feel judgements", the statement that a duration "feels longer" than a person knows it to be, (c) distortions of passage of time in emergency situations, (d) passage of time and ageing, and (e) determinants of POTJs, particularly the roles of information-processing/attention and arousal.

The remembrance of times past: interference in temporal reference memory.

Six experiments examined human performance on a modified temporal generalization task when either 1 or 2 standard durations were encoded. In most conditions, participants were presented with a 1st standard duration (A), then judged whether a number of comparison stimuli had the same duration as A. They were then presented with a 2nd standard (B) and again judged whether other comparison stimuli had the same duration as B. Then, after a delay period of 0-45 s, further comparison stimuli were presented, and participants judged whether those stimuli had the same duration as A, without A being represented. A was either the same length as B or shorter or longer than it, so potential retroactive interference effects of B on A could be examined. After a short delay before retesting of A comparisons, the peak of the temporal generalization gradient shifted toward the shortest of the comparisons when A < B and the longest when A > B. The results suggest that certain combinations of delay and interference might render the memory of A unusable, so that a new standard is constructed on the basis of the remembered relationship between A and B, a kind of "false memory" for duration.

Stimulus timing by people with Parkinson's disease.

Previous literature suggests that Parkinson's disease is marked by deficits in timed behaviour. However, the majority of studies of central timing mechanisms in patients with Parkinson's disease have used timing tasks with a motor component. Since the motor abnormalities are a defining feature of the condition, the status of timing in Parkinson's disease remains uncertain. Data are reported from patients with mild to moderate Parkinson's disease (both on and off medication) and age- and IQ-matched controls on a range of stimulus timing tasks without counting. Tasks used were temporal generalization, bisection, threshold determination, verbal estimation, and a memory for duration task. Performance of patients was generally "normal" on all tasks, but significant differences from performance of controls were found on the memory for duration task. Among the "normal" effects noted were arithmetic mean bisection, asymmetric temporal generalization gradients, and subjective shortening on the memory for duration task. The results suggest (a) that some previous reports of timing "deficits" in Parkinson's patients were possibly due to the use of tasks requiring a timed manual response and (b) small differences between patients and controls may be found on tasks where two stimuli are presented on each trial, whether patients are on medication or off it.

Detectability and criterion measures in temporal generalization.

Computer simulation of performance on "normal" and "episodic" temporal generalization tasks was used to examine the relations between the theoretical parameters of models which fit temporal generalization data ("timing sensitivity" and "threshold"), and the d' (detectability) and beta (decision criterion) measures of signal-detection theory. In general, changes in timing sensitivity altered d', whereas threshold changes affected beta, supporting the assertion that the two sorts of variables ("sensitivity/detectability" and "threshold/criterion") were psychologically equivalent. Cases where temporal generalization gradients were apparently contaminated by "random responding" could be treated by changes in beta, but cases in which temporal generalization gradients were not peaked at the standard posed severe problems for a simple signal-detection account, although existing models of temporal generalization performance could deal with them.

When to respond? And how much? Temporal control and response output on mixed-fixed-interval schedules with unequally probable components.

Rats were trained on mixed-fixed-interval (FI) schedules, with component FIs of 30 and 60s. The probability of reinforcement according to FI 30s varied between conditions, across values of 0.1, 0.3, 0.5, 0.7 and 0.9. When response rate in the 60s intervals was measured, separate response peaks, one close to 30s, the other at 60s, could be identified when the probability of reinforcement at 30s was 0.3 or greater. Nonlinear regression found that the location of the earlier peak was always close to 30s, that the coefficient of variation of the response functions at 30 and 60s were unaffected by reinforcement probability, but that the 30s component appeared to be timed slightly more precisely than the 60s one. Response rate at around 30s increased with increasing probability of reinforcement according to FI 30s, but responding at 60s was unaffected by reinforcement probability. The data are discussed with respect to a number of contemporary models of animal timing (scalar expectancy theory, the Behavioural Theory of Timing and the Learning to Time model), and a recent account of response output on FI-like schedules.

Effects of feedback and calibration on the verbal estimation of the duration of tones.

Two experiments investigated the effects of feedback (Experiment 1) and calibration (Experiment 2) on verbal estimation of the duration of tones ranging from 77 to 1183 ms in length. In Experiment 1, accurate feedback was provided after half the trials in the feedback condition, and this was contrasted with a no-feedback condition in which feedback was absent. In Experiment 2, in the calibration condition, participants estimated the duration of the second of two tones, after a first tone of a known duration (ranging from 50 to 1200 ms) had been presented. In the no calibration condition the value of the first tone was unknown. Compared with conditions without feedback or calibration, the feedback/calibration operation produced no significant change in group mean estimates, nor coefficients of variation of estimates, but the absolute deviation of estimates from the real stimulus duration, and the absolute deviation of individual estimates from the group mean, were both significantly reduced. The feedback/calibration thus made participants' mean estimates thus more accurate and more similar to one another, but the actual mechanism by which this was done was apparently a subtle process of adjustment, rather than a gross change in mean estimate or estimate variability.

What speeds up the internal clock? Effects of clicks and flicker on duration judgements and reaction time.

Four experiments investigated the effect of pre-stimulus events on judgements of the subjective duration of tones that they preceded. Experiments 1 to 4 used click trains, flickering squares, expanding circles, and white noise as pre-stimulus events and showed that (a) periodic clicks appeared to "speed up" the pacemaker of an internal clock but that the effect wore off over a click-free delay, (b) aperiodic click trains, and visual stimuli in the form of flickering squares and expanding circles, also produced similar increases in estimated tone duration, as did white noise, although its effect was weaker. A fifth experiment examined the effects of periodic flicker on reaction time and showed that, as with periodic clicks in a previous experiment, reaction times were shorter when preceded by flicker than without.

"The stone which the builders rejected...": Delay of reinforcement and response rate on fixed-interval and related schedules.

The article deals with response rates (mainly running and peak or terminal rates) on simple and on some mixed-FI schedules and explores the idea that these rates are determined by the average delay of reinforcement for responses occurring during the response periods that the schedules generate. The effects of reinforcement delay are assumed to be mediated by a hyperbolic delay of reinforcement gradient. The account predicts that (a) running rates on simple FI schedules should increase with increasing rate of reinforcement, in a manner close to that required by Herrnstein's equation, (b) improving temporal control during acquisition should be associated with increasing running rates, (c) two-valued mixed-FI schedules with equiprobable components should produce complex results, with peak rates sometimes being higher on the longer component schedule, and (d) that effects of reinforcement probability on mixed-FI should affect the response rate at the time of the shorter component only. All these predictions were confirmed by data, although effects in some experiments remain outside the scope of the model. In general, delay of reinforcement as a determinant of response rate on FI and related schedules (rather than temporal control on such schedules) seems a useful starting point for a more thorough analysis of some neglected questions about performance on FI and related schedules.

About Skinner and time: behavior-analytic contributions to research on animal timing.

The article discusses two important influences of B. F. Skinner, and later workers in the behavior-analytic tradition, on the study of animal timing. The first influence is methodological, and is traced from the invention of schedules imposing temporal constraints or periodicities on animals in The Behavior of Organisms, through the rate differentiation procedures of Schedules of Reinforcement, to modern temporal psychophysics in animals. The second influence has been the development of accounts of animal timing that have tried to avoid reference to internal processes of a cognitive sort, in particular internal clock mechanisms. Skinner's early discussion of temporal control is first reviewed, and then three recent theories-Killeen & Fetterman's (1988) Behavioral Theory of Timing; Machado's (1997) Learning to Time; and Dragoi, Staddon, Palmer, & Buhusi's (2003) Adaptive Timer Model-are discussed and evaluated.

Cognitive abilities required in time judgment depending on the temporal tasks used: A comparison of children and adults.

The aim of this study was to examine age-related differences in time judgments during childhood as a function of the temporal task used. Children aged 5 and 8 years, as well as adults, were submitted to 3 temporal tasks (bisection, generalization and reproduction) with short (0.4/0.8 s) and long durations (8/16 s). Furthermore, their cognitive capacities in terms of working memory, attentional control, and processing speed were assessed by a wide battery of neuropsychological tests. The results showed that the age-related differences in time judgment were greater in the reproduction task than in the temporal discrimination tasks. This task was indeed more demanding in terms of working memory and information processing speed. In addition, the bisection task appeared to be easier for children than the generalization task, whereas these 2 tasks were similar for the adults, although the generalization task required more attention to be paid to the processing of durations. Our study thus demonstrates that it is important to understand the different cognitive processes involved in time judgment as a function of the temporal tasks used before venturing to draw conclusions about the development of time perception capabilities.

Undernutrition of weanling and adult rats: effects on operant responding.

In the rat, brain growth is most vulnerable to undernutrition during the suckling period. Undernutrition at that stage also produces lasting effects on behaviour and it is often assumed that these are due to disturbances of brain growth. The proposal that this may not necessarily be so was explored by testing the behaviour of rats which had been undernourished at later stages of life and which, therefore, would be expected to show little or no deficit in brain growth. Rats were undernourished either immediately after weaning (25-67 days) or in adulthood (80-134 days) and were tested 3-4 months later on variable interval and variable ratio schedules of reinforcement with food as the reward. Their behaviour on these schedules was similar to that of rats undernourished during the suckling period: both groups responded or tended to respond at a higher rate than controls. Hence, it is possible that undernutrition at any stage in life may make animals more responsive to food when deprived subsequently. A cognitive mechanism for this change in behaviour is suggested.

Temporally spaced responding for food in adult rats after undernutrition early in life.

Rats were undernourished during the suckling and early post-weaning periods and were then fed a good quality diet ad libitum from 43 to 300 days when behavioural testing was begun. Male previously undernourished and control rats were tested on three operant conditioning schedules in which low rates of bar-pressing were rewarded with food (differential reinforcement of low rate or DRL schedules). These were DRL 5 sec, DRL 10 sec and DRL 30 sec. On each schedule the response rates of both groups of animals declined over several sessions and their efficiency at obtaining the food rewards increased. However, there were no significant differences between the two groups on either of these measures. This finding indicates that, despite being hyper-responsive in many situations, including some operant conditioning schedules, previously undernourished rats are as capable as controls of withholding responding when necessary.

Traveling in time: a time-left analogue for humans.

Two experiments studied normal humans in an analogue of the time-left procedure of J. Gibbon and R. M. Church (1981). In Experiment 1 the "standard" alternative (S) was always half the length of the "comparison" time-left link (C), and S ranged from 4 to 8 s. Humans showed an increasing preference for the time-left alternative with increasing elapsed time in the interval, and indifference points strongly supported the idea of a linear, rather than a logarithmic, time scale. Experiment 2 used some conditions in which S was greater or less than C/2, and preference for the time-left alternative varied systematically with the S/C ratio. Data from both experiments showed reasonable superposition, suggesting underlying scalar timing processes in time left in humans.

Categorical scaling of stimulus duration by humans.

Normal human adults performed on an analogue of the categorical timing procedure, used by J.G. Fetterman and P.P. Killeen (1995) with pigeons, by classifying a set of 18 or 24 tone durations in 3 or 4 categories. Use of the different categories was an orderly function of stimulus duration in all cases, and data showed a close approximation to superposition, indicating conformity to scalar timing. Both these results were similar to data from pigeons. A model using memory representations of the category-range geometric means with scalar variance fitted data well in nearly all respects. The results emphasize human and animal similarities in categorical timing and conformity of human behavior to scalar timing principles.

Multiple-interval timing in rats: Performance on two-valued mixed fixed-interval schedules.

Three experiments studied timing in rats on 2-valued mixed-fixed-interval schedules, with equally probable components, Fixed-Interval S and Fixed-Interval L (FI S and FI L, respectively). When the L:S ratio was greater than 4, 2 distinct response peaks appeared close to FI S and FI L, and data could be well fitted by the sum of 2 Gaussian curves. When the L:S ratio was less than 4, only 1 response peak was usually visible, but nonlinear regression often identified separate sources of behavioral control, by FI S and FI L, although control by FI L dominated. Data were used to test ideas derived from scalar expectancy theory, the behavioral theory of timing, and learning to time.

Scalar timing in temporal generalization in humans with longer stimulus durations.

Three experiments investigated temporal generalization performance in humans by using stimulus durations similar to those previously used with rats. In most conditions, chronometric counting was prevented by concurrent shadowing of temporally irregular numbers. Experiment 1 examined performance with visual stimuli, when the standard was 4.0 s long and nonstandard stimuli were spaced either linearly or logarithmically around the standard. Generalization gradients were asymmetrical with linear spacing but symmetrical with logarithmic spacing, a result obtained previously with humans. Experiment 2 used auditory stimuli and varied the standard across values of 2.0, 4.0, 6.0, and 8.0 s. All gradients were asymmetrical, and good superposition was obtained, indicating conformity to scalar timing. Experiment 3 prevented or encouraged chronometric counting by changing instructions, and temporal generalization gradients differed when counting was and was not used.

Speeding up an internal clock in humans? Effects of click trains on subjective duration.

Four experiments investigated the effect of trains of clicks (usually 5 s long and at 5 or 25 Hz) on subjective duration in humans, as previous research had suggested that such a manipulation would speed up the pacemaker of an internal clock by increasing participants' arousal. The four experiments used temporal generalization, pair comparison of duration, verbal estimation, and production of short durations. In all cases, preceding the durations to be judged by clicks changed their subjective length in a manner broadly consistent with the idea that pacemaker speed was increased, by an average of about 10%.

Adjusting to changes in the time of reinforcement: peak-interval transitions in rats.

Thirty rats received training on a peak-interval procedure, where a baseline with a 20-s time of reinforcement was interspersed among cyclic transitions to other reinforcement time values (10, 20, 30, or 40 s), each of which was either in force for only a single session or for 3 sessions. Peak times were close to the time of reinforcement on the 20-s baseline and tracked the new reinforcement times both closely (but not exactly) and very rapidly. Peak time during transitions was affected by the criterion value in force on the previous session, exhibiting a proactive interference effect. Analysis of individual peak times during a session showed that transitions from lower to higher reinforcement time values were usually characterized by abrupt jumps in peak time, whereas descending transitions were mostly smooth but rapid.

Differences between rats and undernourished preweaning, and controls in learning about a redundant stimulus during acquisition of a conditioned emotional response.

Male rats were undernourished during the first three weeks of life by restricting maternal food consumption. Following nutritional rehabilitation, previously undernourished (PU) and control (C) rats were trained to operate a lever to obtain food reward on a variable interval schedule. When rates of responding had stabilised, the rats were tested for suppression of lever-pressing during the illumination of a light which preceded footshock. There were not differences between PU and C groups in the acquisition of this conditioned emotional response, nor were there differences in suppression when a redundant, tone stimulus was presented contemporaneously with the light to predict shock. When the tone was subsequently tested alone for its ability to suppress lever-pressing it was found to have acquired this property in C, but not in PU animals. In a second experiment, PU and C rats were found not to differ in their response to the tone when it was presented as a novel stimulus, nor in suppression to the tone when it was made the sole predictor of footshock. It was concluded that PU and C rats differed in learning about a stimulus predicting footshock, only when that stimulus was redundant. Among the possible explanations for this behavioural difference between PU and control rats are differences in motivation, curiosity, or strength of conditioning. These possibilities are evaluated within the context of current formal theories of conditioning.