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.     

Duration discrimination of empty time intervals marked by intermodal pulses

In 1973, Rousseau and Kristofferson reported that short empty intermodal time intervals marked by a light flash and a brief tone were poorly discriminated by subjects, and that AT,5 was constant over a large range of durations. It led them to suggest that short intramodal empty intervals, marked by stimuli from the same sensory modality, might be handled by a “more efficient mechanism” to which intermodal intervals would not have access. Unfortunately, their study lacked the basic evidence needed to make a strong statement: no direct comparison between inter- and intramodal duration discrimination and no within-subject discrimination function were available. To clarify these two issues, three experiments were performed. The data indicate that intermodal time intervals are discriminated more poorly than intramodal ones, and that intermodal duration discrimination functions follow Weber’s law. Analysis of data from different experiments lead to the conclusion that inter- and intramodal intervals are timed by a common timekeeper and that intermodal intervals induce a large noise component in the timekeeping operation.

     

Attention sharing during timing: modulation by processing demands of an expected stimulus

Varying the location of a nontemporal task during a time estimation task affects temporal estimates. Previous studies have also shown that manipulating the location of a stimulus to ignore may disturb timing similarly, suggesting that the effect might be independent of the processing requirements in the nontemporal task. In Experiment 1, the location of a tone varied during a 2-sec interval production; participants were asked either to ignore the tone or to discriminate its frequency. Productions were longer when the tone was presented later, but only when it was processed. In Experiment 2, short and long tones corresponding to more or less difficult discrimination tasks were used. The location effect was stronger and remained stronger throughout the experiment when participants were tested with the short tone in the first experimental session than when they were tested with the long tone first. These results suggest that timing is influenced by relatively stable attention-sharing strategies.     

A real-time criterion theory of duration discrimination

The common idea that a measure is taken of a duration stimulus over its temporal extent, and that the decision as to whether the stimulus is relatively long or short is based upon such a measure, is shown to be incorrect. Two experiments, which require speeded responding in duration discrimination and consider response latencies as well as response probabilities, demonstrate that the response that is made is determined by the outcome of a race between an internally timed interval, the criterion, and the presented stimulus. The onset of the stimulus triggers the criterion; if the criterion ends first, the response “long” is elicited. Duration discrimination is a matter of temporal order discrimination, and in the limit, “short” responses are simple reactions while “long” responses are time estimation responses. A specific model of the real-time criterion hypothesis is tested, and these initial tests generally confirm it. From this, it is concluded that errors in duration discrimination are due entirely to variability of the criterion and that afferent latencies are not necessarily variable. This adds additional evidence for the existence of deterministic afferent latencies.     

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.     

Generalization and response latency

The present experiments investigated generalization in a reaction time situation where the generalization stimulus, a tone, preceded the reaction time signal, a light. The hypotheses under investigation were that the duration of the cue stimulus would determine the degree of generalization (Experiment I) and that the response latency independent of the stimulus duration would be related to the amount of generalization (Experiment II). A particular generalization test stimulus (a tone of 40, 45, 50, 60, 65, or 70 dB) was presented only once always following two bar-pressing responses to training stimulus (tone of 55 dB) under each of two conditions of stimulus duration in Experiment I and under each of two conditions of response latency in Experiment II. It was found that under the condition of short response latency generalization was broader.     

Temporal course of perceived auditory duration

A series of experiments explored the temporal course of the perceived duration of an auditory stimulus. A backward recognition masking paradigm was utilized, in which the subject was to determine which of two target durations was presented on a given trial. The target tone was followed, after a variable silent intertone interval, by a masking tone which could assume one of three possible durations. Identification of the long target was found to improve consistently with increases in the intertone interval. In contrast, identification of the short target was as accurate at the short as at the long intertone intervals. Blocking the intertone interval across experimental sessions eliminated these differences between the two target tones. Performance on both the long and the short target tones improved monotonically with increases in the intertone interval. When masking tone duration was randomized within an experimental session, identification of the long (short) target was most accurate with the longer (shorter) masking tone. Blocking the duration of the masking tone across experimental sessions eliminated the effect of the duration of the mask, but did not alter any of the other results. A model, proposed to account for the results, assumes that the percept of target duration grows over time, and can be terminated by the onset of the masking tone. The masking tone also acts to lengthen the perceived duration of the target tone, and this lengthening is a direct function of the duration of the masking tone.     

Generalization and response latency

The present experiments investigated generalization in a reactio? time situation where the generalization stimulus, a tone, preceded the reaction time signal, a light. The hypotheses under investigation were that the duration of the cue stimulus would determine the degree of generalization (Experiment I) and that the response latency independent of the stimulus duration would be related to the amount of generalization (Experiment II). A particular generalization test stimulus (a tone of 40, 45, 50, 60, 65, or 70 dB) was presented only once always following two bar-pressing responses to training stimulus (tone of 55 dB) under each of two conditions of stimulus duration in Experiment I and under each of two conditions of response latency in Experiment II. It was found that under the condition of short response latency generalization was broader.     

Temporal discrimination as a function of marker duration

In a series of three experiments, the effect of marker duration on temporal discrimination was evaluated with empty auditory intervals bounded by markers ranging from 3 to 300 msec or presented as a gap within a continuous tone. As a measure of performance, difference thresholds in relation to a base duration of 50 msec were computed. Performance on temporal discrimination was significantly better with markers ranging from 3 to 150 msec than with markers ranging from 225 to 300 msec or under the gap condition. However, within each range of marker duration (3–150 msec; 225–300 msec or gap) performance did not differ significantly. A fourth experiment provided evidence that the effect of marker duration cannot be explained in terms of marker-induced masking. A good approximation of the relationship between marker duration and temporal discrimination performance in the present experiments is a smooth step function, which can account for 99.3% of the variance of mean discrimination performance. Thus, the findings of the present study point to the conclusion that two different mechanisms are used in the processing of temporal information, depending on the duration of the auditory markers. The tradeoff point for the hypothetical shift from one timing mechanism to the other may be found at a marker duration of approximately 200 msec.     

The locus of redundant-targets and nontargets effects: evidence from the psychological refractory period paradigm

In target detection tasks, responses are faster when displays have 2 targets (redundant-targets effect; RTE) and slower when they have no targets (nontargets effect; NTE) relative to displays with a single target. The psychological refractory period paradigm was used to localize these effects. In Experiment 1, participants classified tones as high or low and then classified letters as targets or nontargets after a short or long stimulus onset asynchrony (SOA). The magnitudes of the RTE and NTE did not depend on SOA. In Experiment 2, the order of the tasks was reversed, and at short SOAs the RTE and NTE had similar magnitudes for both tone discrimination and target detection responses. These findings suggest that the RTE and NTE arise during response selection. Interactive effects of tone pitch with the number and type of target features were also observed, and these were tentatively interpreted as synesthetic effects.     

Airflow as a discriminative stimulus

In one experiment, pigeons were taught to discriminate airflow by having availability of reinforcement signalled by its presence and extinction signalled by its absence. After they reached criterion, some were trained on a discrimination reversal. Others were trained on an intradimensional discrimination with a low airflow velocity associated with reinforcement and a higher airflow velocity associated with extinction. All discriminations were learned rapidly, indicating that airflow velocity can function as a discriminative stimulus. In the second and third experiments, naive pigeons were trained to discriminate the presence of a compound stimulus (one of three tonal intensities paired with one of three airflow velocities) from its absence. These pigeons were subsequently given a component stimulus test during extinction on four stimulus values; the two training values, the tone alone, and the airflow alone. High or moderate velocity airflow controlled more responding than any of the three tone intensities. However, low velocity airflow controlled more responding only when a low intensity tone was employed.     

Switching or sharing in dual-task line-length discrimination?

In two experiments, we tested whether subjects switched or shared attention between two simultaneously relevant line-length discrimination tasks. Switching models that allowed within- as well as between-trial switching were considered. In the first experiment, stimulus duration was varied randomly from trial to trial. With varied durations, many switching models predict negative contingencies: for a given duration and attentional allocation, accurate responses on one task should be associated with inaccurate responses on the other task. The results, however, showed no negative contingencies, which is consistent with sharing models. In the second experiment, stimulus duration was reduced to 20 msec, yet responses were more than 75% correct overall. This implies that information was obtained about both of the tasks within single trials, contradicting those switching models which predict that information can be obtained from, at most, one task within a period of 20 msec or less. In short, the results of both experiments support sharing models.     

The control of responding by auditory stimuli: interactions between different dimensions of the stimuli.

Sounds have position in addition to other dimensions, such as intensity and frequency. Position rapidly gains control of spatially contiguous responses and this may interfere with control of responding by other acoustic dimensions. These experiments investigated interference of a tone-noise discrimination by the discrimination of acoustic position. Squirrel monkeys were studied when responding was differentially reinforced in the presence of both spectral content (tone-noise) and positional differences between the stimuli, and when responding was differentially reinforced only in the presence of spectral differences. Under the first condition, responding rapidly came under the control of the position of the noise in the two monkeys tested. The position of the tone controlled responding in one monkey; in the second monkey, responding came under the control of the spectral content of the tone. Under the second condition, responding was initially under the control of the noise in all three monkeys tested. This persisted for the duration of the condition for two of the monkeys; in one monkey, responding came under the control of the spectral content of the noise. Under the second condition, responding was also initially under the control of the position of the tone for all monkeys, but control by spectral content of the tone relatively rapidly developed in two of three monkeys.     

The role of R-S1 expectancy in discrimination and discrimination reversal learning

Four experiments assessed the role of response-reinforcement (R-S¹) expectancy as rats either learned a discrimination or a discrimination reversal. Experiment 1 showed that the higher the percentage of reinforcement during nondiscriminative pretraining the more quickly a subsequent discrimination is learned. Experiment 2 demonstrated that the overlearning reversal effect (ORE) can be obtained even though the overtraining phase consists of responses to a single neutral card. In Experiment 3 subjects were again overtrained on a single neutral stimulus under conditions of varying reinforcement. ORE was apparent under reinforcement of a high percentage of responses but was not apparent under reinforcement of a low percentage. Experiment 4 revealed that the fewer errors a subject makes prior to reversal the better its reversal performance is. Results of these studies were discussed in terms of generalized attention theories and the expectancy notions of Bolles (Psychological Review, 1972, 79(5), 394–409.     

Large and rapid improvement in form discrimination accuracy following a location precue

Processing of a visual stimulus can be improved by precuing its location. Most previous precue studies have used reaction time as the dependent measure and have found large effects; but when form discrimination accuracy has been used, precue effects have been relatively small. The present experiments yielded large, short-latency precue effects on form discrimination accuracy. A small square precue was briefly presented near one of four possible target locations. Then one of four possible targets (T-like figures) was presented in each location, followed by a mask. Observers attempted to identify the target that had been presented in the cued location. In experiment 1, target duration, cue-to-target distance, and cue-target onset asynchrony (SOA) were varied. Target discriminability (d') increased markedly with increasing precue-target SOA, even at very short SOAs. Thus, there was no evidence for a delay in the onset of precue effects (caused, for example, by the need to shift attention across the visual field). Performance was best for precues that were closest to the target, thus ruling out a forward masking explanation of the effect. Finally SOA and target duration interacted strongly - longer precue SOAs resulted in larger effects of target duration. In experiment 2, this interaction was replicated using an additional target duration and longer SOAs. One interpretation of this result is that focal attention increases the rate at which information can be extracted from a visual location.     

Signal detection and matching: analyzing choice on concurrent variable-interval schedules.

Pigeons' pecks on a red key and a green key were followed by access to grain according to pairs of concurrent independent variable-interval schedules in a combined signal detection/matching law paradigm. Pecks on the red key were reinforced by the richer variable-interval schedule if a short-duration tone had been presented; pecks on the green key were reinforced by the richer variable-interval schedule if a long-duration tone had been presented. Pecks on the green key given a short-duration tone, or on the red key given a long-duration tone, were reinforced by the leaner variable-interval schedule. The data were analyzed according to both signal detection's and the matching law's separate measures of, first, the discrimination of the choices and, second, the bias to make one response or another. Increasing the difficulty of the tone-duration discrimination decreased both methods' measures of the discrimination of the choices and did not change both methods' measures of the bias to make one response or another. Changing the leaner variable-interval schedule so that it approached the richer variable-interval schedule decreased signal detection's measure of discrimination but left its measure of response bias and the matching law measures unchanged. Data collected only until a subject's first changeover response following presentation of a long or a short tone showed higher values for both methods' measures of discrimination, no change in signal detection's measure of response bias, and lower values for the matching law's measure of response bias. Relationships between the matching law's and signal detection's methods of analyzing choice are discussed. It is concluded that a signal detection analysis is more efficient for examining changes in the difficulty of a discrimination, whereas a matching law analysis is more effective for examining the effects of changes in relative reinforcer frequency.     

Expected endings and judged duration

In four experiments, the predictions of an expectancy/contrast model (Jones & Boltz, 1989) for judged duration were evaluated. In Experiments 1 and 2, listeners estimated the relative durations of auditory pattern pairs that varied in contextual phrasing and temporal contrast. The results showed that when the second pattern of a pair either seems to (Experiments 1 and 2) or actually does (Experiment 2) end earlier (later)than the first, subjects judge it as being relatively shorter (longer). In Experiment 3, listeners heard single patterns in which notes immediately preceding the final one were omitted. Timing of the final (target) tone was varied such that it was one beat early, on time, or one beat late. Listeners’ ratings of target tones revealed systematic effects of phrasing and target timing. In Experiment 4, listeners temporally completed (extrapolated) sequences of Experiment 3 that were modified to exclude the target tone. The results again showed that phrase context systematically influenced expectancies about “when” sequences should end. As a set, these studies demonstrate the effects of event structure and anticipatory attending upon experienced duration and are discussed in terms of the expectancy/contrast model.     

Memory for sequences of tone bursts in the rat: Reliance on temporal cues and evidence for an instructional ambiguity explanation of the choose-few effect

Two groups of rats were trained in a symbolic delayed matching-to-sample task with a 0-s delay to discriminate sample stimuli that consisted of sequences of tone bursts. For one group, sequences varied in number with total sequence duration controlled. For the other group, total sequence duration, sum of the tone durations, and sum of the gap durations were all controlled. The former group of rats acquired the discrimination, but the latter group of rats were not able to learn the discrimination with the additional temporal cues controlled. Retention functions for the group that acquired the discrimination exhibited a choose-many bias at the 1-s delay and a choose-few bias at the 8-s delay regardless of the similarity in the intertrial interval and delay interval illumination condition. The asymmetrical retention functions appeared to be due to instructional ambiguity which resulted from the similarity of the delay interval to temporal features of the tone burst sequence, such as the gap between tone bursts and the total duration of tone. In Experiment 2, diagnostic tests provided evidence that rats discriminated the sequences of tone bursts by timing and summing the duration of individual tone bursts rather than using an event switch to count tones. Like pigeons, rats use multiple temporal features rather than number to discriminate sequences of successive events.     

Directing spatial attention towards the illusory location of a ventriloquized sound

In this study, we examined whether ventriloquism can rearrange external space on which spatial reflexive attention operates. The task was to judge the elevation (up vs down) of auditory targets delivered in the left or the right periphery, taking no account of side of presentation. Targets were preceded by either auditory, visual, or audiovisual cues to that side. Auditory, but not visual cues had an effect on the speed of auditory target discrimination. On the other hand, a ventriloquized cue, consisting of a tone in central location synchronized with a light flash in the periphery, facilitated responses to targets appearing on the same side as the flash. That effect presumably resulted from the attraction of the apparent location of the tone towards the flash, a well-known manifestation of ventriloquism. Ventriloquism thus can reorganize space in which reflexive attention operates.     

Effects of awareness and motor involvement on autonomic conditioning in chronic schizophrenics

Chronic schizophrenics under neuroleptic medication were compared with normals, matched for age and education, in two conditioning experiments. Both experiments employed a differential paradigm with long conditional stimulus-unconditional stimulus (CS-UCS) intervals. Skin resistance (SR) and finger pulse or heart rate (HR) were recorded. In Experiment 1, half of the subjects were trained in categorizing the to-be conditional stimuli. In a further step, half of the subjects were informed about the CS-UCS contingency. The UCS was an electric shock. Information improved discrimination of SR responses only of normals, and discrimination training had no effect at all on autonomic responses. In Experiment 2, only electrodermal responders were included. Each subject was tested in two sessions, using a loud tone as UCS in one, and a reaction time signal in the other. Again, half of the subjects were informed about the contingency. Information improved discrimination of SR responses of both diagnostic groups. Decelerations of HR following CS onset showed informed schizophrenics to discriminate better with the loud tone UCS than with the reaction time signal. General autonomic responsivity seems to determine not only discriminative conditioning of schizophrenic patients but also the reports of awareness and the effects of manipulations of awareness. However, when subjects are matched for electrodermal responsivity and are equivalent in terms of SR response conditioning, patients react to information about the contingency with enhanced HR deceleration to the CSs, possibly reflecting a heightened sensitivity of the cardiovascular system.