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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual influences on crossover in the reaction time performance of schizophrenics.

Conducted 3 investigations with a total of 55 female process schizophrenics and 54 normal controls to test the resilience of the crossover phenomenon observed in schizophrenic reaction time performance. The crossover effect portrays an interaction of the predictability (regularity) and the duration of the delay (preparatory interval) factors in the simple reaction time procedure. The effect, believed pathognomonic of schizophrenic reaction time performance, shows performance on regular trials to be faster than irregularly presented trials at short duration, but the regular presentation of trials is slower at longer duration preparatory intervals. The present studies tested an interpretation that the difference between the regular and irregular trials with long preparatory intervals might be dependent on the influence of certain contextual influences operating within the arrangement of trials. Findings show that the contextual factors studied did not account for this difference. Neither eliminating the presence of shorter trials preceding the irregular test trials nor loading the series with short duration trials substantially influenced the extent to which the long regular trials were slower than the long irregular trials. As observed before, the crossover characterized the process schizophrenic group and was not characteristic of the reactive schizophrenic or normal control groups. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Internal clock and memory processes in animal timing.

Two experiments, involving a total of 6 male pigeons, investigated temporal control of behavior within the framework of an internal clock model. Ss were exposed to signaled fixed interval (FI) 30-sec trials mixed with extended unreinforced (baseline) trials. On unreinforced break trials, the signal was interrupted for a period of time after trial onset. In Exp 1, comparisons between the peak time obtained on baseline and on break trials produced peak time shifts that were longer than those expected if the clock had stopped during the break but shorter than if the clock had reset. In Exp 2, systematic manipulations of duration and location of breaks produced peak time shifts that were nonlinear functions of break duration and that varied linearly with break location. The obtained peak times were more consistent with a continuous memory decay model than with the stop-retain or the reset hypotheses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Break Expectancy in Duration Discrimination.

Effects of break expectancy, observed previously in time production, were examined in 3 experiments using a discrimination paradigm. Participants classified a tone as being short or long. Location and duration of breaks in tone presentation were varied. Proportion of short responses increased as the break occurred later in the duration to be estimated in all experiments. With a higher number of break locations covering a wider range of location values, functions relating proportion of short responses to location were sigmoid and tended to flatten at extreme values of location. The authors conclude that attentional time-sharing elicited by break expectancy induces loss in accumulation of temporal information, but its effect on discrimination depends on the accumulation outcome relative to a decisional criterion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention deficits in childhood-onset schizophrenia: Reaction time studies.

The hypothesis of continuity between childhood-onset and adult schizophrenia was tested by comparing the performance of 15 patients with childhood-onset schizophrenia and 52 age-matched controls on 2 reaction time paradigms that have been used to study adult schizophrenia. On simple reaction time to tones with regular and irregular preparatory intervals of 2, 4, and 8 s, patients showed greater effects of the length of the preparatory interval in the regular condition and greater effects of the preparatory interval (girls only) and the preceding preparatory interval in the irregular series. On simple reaction time to random lights and tones, patients were faster on sequences than cross-modal sequences compared with controls. Overall, patients were much slower than controls in both paradigms. The results suggest similar attention dysfunction as is found in adult schizophrenia and thus are consistent with the continuity hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related differences in timing with breaks.

Two groups of participants differing in age were compared on a time production task during which timing was temporarily interrupted. Produced intervals lengthened with increasing delay before the break occurrence, and the effect was more pronounced in older than in younger adults. A reaction time response to the signal beginning the break period was required also. Older participants responded more slowly to this signal, but they benefited to a greater extent from a lengthening of the time preceding its presentation. These results suggest that performance of older participants is affected by attention sharing and preparation involved in timing with breaks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relation entre le niveau d'excitabilite medullaire et la probabilite conditionnelle d'apparition du signal d'execution pendant la periode preparatoire a une reponse motrice.

Many experimental facts confirm the hypothesis that the relation between the duration of the preparatory period, and the performance level obtained in an RT situation, partly depends on the conditional probability of the response signal. This study shows that the effects of such a variable appear in physiological changes accompanying the preparatory sets, especially the excitability of the spinal motor structures. The level of spinal excitability has been tested by the monosynaptic reflexes method, with Ss placed in a simple RT situation, during the period separating the preparatory from the response signal, or the preparatory signal from the preceding response. In both procedures the interval explored was systematically varied and the time uncertainty concerning the moment of occurrence of the awaited signal was rendered independent of the duration of the interval by the use of a periodic stimulus acting as a time mark. A positive relation was observed between the duration of the variable interval and the amplitude of the spinal reflexes. It was indentical in the 2 procedures when exploration concerned a muscle which was not involved in carrying out the response. The development of the spinal excitability level for the muscle involved in carrying out the response differs according to the meaning of the awaited signal: it grows during the interval between the trials. Results show the double aspect of the preparatory phenomena, of activating and generalized nature and, of lowering and focused nature. The hypothesis is confirmed in both cases. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Manual and saccadic reaction time with constant and variable preparatory intervals in schizophrenia.

Saccadic reaction time (RT) has been shown to be unimpaired in schizophrenia. Could this be due to its not requiring controlled information processing? The authors gave 49 schizophrenia patients and 34 controls manual and saccadic RT tasks with preparatory intervals of 1, 3, and 5 s given in regular and irregular sequences. If saccades require mainly automatic processes, they should not be affected by variations in the preparatory interval that are mediated by controlled processing. The manual task showed typical slower RT and larger preparatory interval effects in patients than in controls. Although the saccadic task showed significant effects of both the preparatory interval and the preparatory interval on the preceding trial similar in kind to those in manual RT, there were no group differences in these or in RT. The results are attributed to greater stimulus-response compatibility in the saccadic task, which puts fewer demands on working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory for Timing Visual and Auditory Signals in Albino and Pigmented Rats.

The authors hypothesized that during a gap in a timed signal, the time accumulated during the pregap interval decays at a rate proportional to the perceived salience of the gap, influenced by sensory acuity and signal intensity. When timing visual signals, albino (Sprague-Dawley) rats, which have poor visual acuity, stopped timing irrespective of gap duration, whereas pigmented (Long-Evans) rats, which have good visual acuity, stopped timing for short gaps but reset timing for long gaps. Pigmented rats stopped timing during a gap in a low-intensity visual signal and reset after a gap in a high-intensity visual signal, suggesting that memory for time in the gap procedure varies with the perceived salience of the gap, possibly through an attentional mechanism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Systematic nonlinearities in the memory representation of time.

The representation of time was investigated by testing rats with intervals that changed by 2 s across trials. In Experiment 1, 2 ranges (20–150 s, 30–160 s; n?=?10 rats per group) were examined. The times at which response bursts occurred (start time) were approximately proportional to interval durations. However, systematic departures from linearity were observed. Nonlinearities were related to the absolute duration of intervals, rather than to durations relative to the range. In Experiment 2, 660-s trials were inserted into the sequence of intervals (10–140 s, n?=?20). Start and end times of response bursts were approximately proportional to intervals, but nonlinearities in start and end times were correlated, indicating that the source of nonlinearity was in the memory representation of time rather than in a decision process. These results indicate that the representation of time is nonlinearly related to physical time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of licking responses in rats: Effects of cholecystokinin and bombesin.

Compared the effects of cholecystokinin (CCK) and bombesin (BBS) on the consummatory response in male albino rats in 3 experiments. The normal licking response pattern did not change as the meal progressed; no predictor was found to indicate when the meal would terminate. Licks normally occurred at about 6/sec, but there were a few licks that occurred at about 3/sec with no licking occurring in the intermediate range; thus, a distinctive bimodal frequency distribution of the interlick interval was formed. CCK reduced the intake of milk and the related licking indices as expected, but it also induced an unusual licking pattern: The contact duration was shortened, the interlick interval was lengthened, and there was an increase in the proportion of licks with long interlick intervals, the effects that accentuated the bimodality of the distribution of interlick intervals. BBS reduced the intake and the related licking indices. The CCK effect may be mediated partially by a change in the motor aspect of the consummatory response; however, BBS reduced intake by simply decreasing the number of licks and shortening the intake duration. BBS may be a candidate for a natural satiety hormone. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How do changes in speed affect the perception of duration?

Six experiments investigated how changes in stimulus speed influence subjective duration. Participants saw rotating or translating shapes in three conditions: constant speed, accelerating motion, and decelerating motion. The distance moved and average speed were the same in all three conditions. In temporal judgment tasks, the constant-speed objects seemed to last longer than the decelerating objects, which in turn seemed to last longer than the accelerating stimuli. In temporal reproduction tasks, the difference between accelerating and decelerating stimuli disappeared; furthermore, watching an accelerating shape lengthened the apparent duration of the subsequent (static) display. These results (a) suggest that temporal judgment and reproduction can dissociate for moving stimuli because the stimulus influences the apparent duration of the subsequent interval, and (b) constrain theories of time perception, including those which emphasize memory storage, those which emphasize the existence of a pacemaker-accumulator timing system, and those which emphasize the division of attention between temporal and non-temporal information processing. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Preceding His-atrial interval as a determinant of atrioventricular nodal conduction time in the human and rabbit heart

This investigation shows that atrioventricular (A-V) nodal conduction time (A-H interval), both in the human and in the isolated rabbit heart, is determined mainly by the length of the preceding His-atrial (H-A) interval. The A-H intervals obtained during atrial extrasystolic stimulation at different basic rates, during Wenckebach cycles and during both transient and steady state responses to stepwise increases in stimulation frequency were plotted against the corresponding H-A intervals. The A-H intervals were found to have nearly the same duration provided they were preceded by the same H-A interval. The only important difference appeared in the short H-A interval range as a shortening of the A-H interval at faster basic rates. This facilitating effect of frequency, which was found in the majority of cases, is compatible with the similarly frequency-dependent shortening of the functional refractory period of the A-V node.     

A simple device for obtaining certain verbal activity measures during interviews.

This paper describes a new instrument devised by G. F. Mahl to determine the duration of time spent talking by the participants in psychotherapy, and the amount of time the patient is silent during successive 2-minute intervals of individual interviews as well as during larger and variable time intervals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Timing in pigeons: Effects of the similarity between intertrial interval and gap in a timing signal.

Previous research suggests that when a fixed interval is interrupted (known as the gap procedure), pigeons tend to reset memory and start timing from 0 after the gap. However, because the ambient conditions of the gap typically have been the same as during the intertrial interval (ITI), ambiguity may have resulted. In the present experiment, the authors found that when ambient conditions during the gap were similar to the ITI, pigeons tended to reset memory, but when ambient conditions during the gap were different from the ITL pigeons tended to stop timing, retain the duration of the stimulus in memory, and add to that time when the stimulus reappeared. Thus, when the gap was unambiguous, pigeons timed accurately. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sources of Variability and Systematic Error in Mouse Timing Behavior.

In the peak procedure, starts and stops in responding bracket the target time at which food is expected. The variability in start and stop times is proportional to the target time (scalar variability), as is the systematic error in the mean center (scalar error). The authors investigated the source of the error and the variability, using head poking in the mouse, with target intervals of 5 s, 15 s, and 45 s, in the standard procedure, and in a variant with 3 different target intervals at 3 different locations in a single trial. The authors conclude that the systematic error is due to the asymmetric location of start and stop decision criteria, and the scalar variability derives primarily from sources other than memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short-term memory and time estimation: Beyond the 2-second "critical" value.

The authors showed previously that when time intervals around two sec are reproduced concurrently with a memory task, intervals are positively related to duration of memory processing. However, some data in research on timing as well as in memory research suggest that 2 sec might be a critical duration beyond which different mechanisms or structures would support performance. This implies that the interference observed between memory processing and 2-sec productions could be specific to these durations, and would not be obtained with longer durations. In this experiment, intervals ranging from 1.85 to 6.45 sec were reproduced by participants (16 females and 12 males, aged 18-33 yrs), who were searching simultaneously for a memory probe. At all durations, reproductions were positively related to memory set size. These findings have implications with regards to previous research indicating a discontinuity around 2-3 sec in time perception. They suggest in particular that the role of memory is similar in reproduction of durations around 2 sec and of longer durations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bisection of temporal intervals by pigeons.

Two experiments investigated temporal bisection in 7 male White King pigeons using a procedure similar to that of D. A. Stubbs (see record 1976-27339-001), which measures the point in time at which the S switches from the shorter to the longer valued of 2 FI reinforcement schedules with a common starting point. Exp I substantiated Stubbs's findings of switching at the geometric mean of the 2 interval values and eliminated the possibility that Ss simply switched to the longer interval when the shorter one was perceived to have expired. The experiment also extended the range of values for which temporal intervals have been found to be bisected at their geometric mean. Exp II demonstrated that the usefulness of the present procedure for determining temporal bisection points is limited to cases in which the longer interval is no more than 4 times the duration of the shorter. Greater separation of the 2 durations produced a period of nonresponding during which the location of the switching or bisection point was totally ambiguous. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal Learning in Random Control Procedures.

Experiments 1 and 2 delivered conditioned stimuli (CSs) at random times and unconditioned stimuli (USs) at either fixed (Experiment 1) or random (Experiment 2) intervals. In Experiment 3, CS duration was manipulated, and US deliveries occurred at random during the background. In all 3 experiments, the mean rate of responding (head entries into the food cup) in the background was determined by the mean US-US interval, and the mean rate during the CS was a linear combination of responding controlled by the mean US-US and mean CS onset-US intervals; the pattern of responding in time was determined by the interval distribution form (fixed or random). An event-based timing account, Packet theory, provided an explanation of the results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal ventriloquism in a purely temporal context.

This study examines how audiovisual signals are combined in time for a temporal analogue of the ventriloquist effect in a purely temporal context, that is, no spatial grounding of signals or other spatial facilitation. Observers were presented with two successive intervals, each defined by a 1250-ms tone, and indicated in which interval a brief audiovisual stimulus (visual flash + noise burst) occurred later. In “test“ intervals, the audiovisual stimulus was presented with a small asynchrony, while in “probe” intervals it was synchronous and presented at various times guided by an adaptive staircase to find the perceived temporal location of the asynchronous stimulus. As in spatial ventriloquism, and consistent with maximum likelihood estimation (MLE), the asynchronous audiovisual signal was shifted toward the more reliably localized component (audition, for all observers). Moreover, these temporal shifts could be forward or backward in time, depending on the asynchrony order, suggesting perceived timing is not entirely determined by physical timing. However, the critical signature of MLE combination—better bimodal than unimodal precision—was not found. Regardless of the underlying model, these results demonstrate temporal ventriloquism in a paradigm that is defined in a purely temporal context. (PsycINFO Database Record (c) 2011 APA, all rights reserved)