Duration estimates of two information processing components

Adult humans attempted to make quick responses to the first of two sequentially presented visual stimuli. At short interstimulus intervals (less than about 100 msec) accuracy was impaired by a different second stimulus and this was hypothesized to reflect the activity of an information processing component concerned with stimulus registration. At longer interstimulus intervals (up to approximately 350 msec) reaction time was inhibited by a different second stimulus and this was assumed to reflect the activity of a second component concerned with decision. The stimulus registration component was insensitive to variations in the complexity of the task, while the decision component was found to be greater for a task requiring recognition (is the current stimulus the same as an earlier one?) than for one merely requiring choice (what is the current stimulus?). This functional independence and the sizeable difference in the temporal range of susceptibility led to the conclusion that two distinct information processing components were involved.     

The effect of first response complexity on the psychological refractory period: A reanalysis

The effect of first signal complexity on the delay of the second response within the paradigm of PRP has been the subject of several recent papers. The results show that, for the same interstimulus interval, the more complex the first reaction, the more the second response is delayed. This paper reports a reanalysis of the data presented by these investigators in terms of comparable response-stimulus intervals. The implications for theories of limited attention are discussed.     

Inhibitory effect of a second stimulus on reaction time to a primary stimulus: a partial successful replication.

A second visual stimulus, to which no response was required, following a primary one lengthened the reaction time to the first stimulus for 25 college students. Reaction time rose as a function of the increase in the interstimulus interval. Duration time of the second stimulus did not affect this response. These results were found under a condition of stimulus-response certainty.     

The stroop effect: Failure to focus attention or failure to maintain focusing?

Subjects matched the position (high or low) of a first stimulus with either the position or the meaning of a word (HI or LO) presented after an interstimulus interval (ISI). The form of the first stimulus (X or O) varied randomly within trial blocks and specified the relevant feature (meaning or position) of the second stimulus to the subject. When the relevant feature was meaning, Stroop interference from the second stimulus position was observed. This interference decreased as ISI increased. At the longest ISI, it was eliminated completely. A number of explanations for these effects are discussed and then tested in two further matching experiments. In a fourth experiment a similar decrease in interference was observed. These reductions in interference with increase in ISI appear to represent the development of attentional focusing on the relevant feature of the second stimulus. Stroop interference may occur in experiments where the relevant attribute is constant because of a difficulty associated with repeated focusing on the same attribute.     

Accuracy of temporal coding: Auditory-visual comparisons

Three experiments were designed to decide whether temporal information is coded more accurately for intervals defined by auditory events or for those defined by visual events. In the first experiment, the irregular-list technique was used, in which a short list of items was presented, the items all separated by different interstimulus intervals. Following presentation, the subject was given three items from the list, in their correct serial order, and was asked to judge the relative interstimulus intervals. Performance was indistinguishable whether the items were presented auditorily or visually. In the second experiment, two unfilled intervals were defined by three nonverbal signals in either the auditory or the visual modality. After delays of 0, 9, or 18 sec (the latter two filled with distractor activity), the subjects were directed to make a verbal estimate of the length of one of the two intervals, which ranged from 1 to 4 sec and from 10 to 13 sec. Again, performance was not dependent on the modality of the time markers. The results of Experiment 3, which was procedurally similar to Experiment 2 but with filled rather than empty intervals, showed significant modality differences in one measure only. Within the range of intervals employed in the present study, our results provide, at best, only modest support for theories that predict more accurate temporal coding in memory for auditory, rather than visual, stimulus presentation.     

Perceptual Anticipation and Reaction Time

To determine the effect of perceptual anticipation upon reaction time, two different types of experiment were carried out. In the first a skilled response had occasionally to be altered at a given point after a variable warning period. In the second the subject had to react to two auditory signals separated by a short time interval which was systematically varied, the second signal being expected or unexpected.

It was found that lack of readiness to respond to a signal, as revealed by a lengthened reaction time, may be due either to the subject not having prepared himself, as he was not expecting the signal; or to the subject not being able to prepare himself in time. Preparation for reacting to the second of the two signals, when both are expected and have to be reacted to, never appears to take more than between 0·2 and 0·4 seconds, as judged by reaction time. On the majority of occasions it appears to be complete in 0·2 seconds. These times are shorter than those usually given, because the extra delay due to incorrect anticipation has been excluded. With intervals of 0·1 seconds or less, delay in the second reaction may be due to the mechanical difficulty of responding quickly enough, especially when the two reactions have to be made in opposite directions.

The finding that lack of readiness might be due to the subject not expecting the signal, and the further finding that preparation took longer when a skilled response had to be extended than when it had to be stopped, both suggest that so-called Psychological refractoriness is due to lack of fore period in which to prepare for the response, rather than to a “Psychological refractory phase” comparable to the refractory phase of nerves. If, by dividing his attention, the subject was able to prepare for his next response while making his previous one, so-called Psychological refractoriness could be completely absent.     

Integration of features in comparing multifeature stimuli

For a series of trials, the subject indicated whether or not two face-like stimuli were identical with respect to the features they contained (a positive or negative response, respectively); reaction time (RT) was recorded. The stimuli were separated by .5 or 4.0 sec, and each contained either two or three features. On some trials, the features of the first stimulus were represented within a single head outline; on others, they were distributed over several spatially separated outlines (components). Positive-response RT increased with the number of stimulus features and with the number of first-stimulus components (c); these two factors were additive. Negative-response RT increased with c, decreased with the number of differing features, and these two factors interacted. These effects did not vary with interstimulus interval. The results indicate that the subject did not integrate the first-stimulus components, but instead compared the second stimulus to each component, holistically (for positive responses) or analytically (for negative responses).     

Tactile perception of sequentially presented spatial patterns

Tactile pattern recognition was studied by presenting pairs of alphabetic shapes in rapid succession at the same anatomical location, the subject being required on each trial to identify bath of the patterns. Experimental variables were the duration of each stimulus and the time between stimuli. Three aspects of the observed interaction were (1) an increase in letter reversals for very short interstimulus intervals; (2) a greater percentage of first-response errors for short-stimulus onset intervals and a greater percentage of second-response errors for long-stimulus onset intervals; and (3) a crossover in the first- and second-response error rates in the range of 100 to 200 msec. after the onset of the first stimulus. These results are consistent with some of the temporal properties of models proposed for analogous visual tasks.     

Concurrence costs in double stimulation tasks

Seven experiments are described on reaction time (RT₁) to a first auditory stimulus in a double stimulation paradigm, where the response to a second visual stimulus was explicitly non-speeded. In all studies it was found that, compared to a single stimulus control condition, RT₁ showed a constant delay of about 20–30 msec. The effect occurred irrespective of (a) the viewing conditions of the second stimulus in terms of either duration, processing demands or presence vs absence of a backward masking signal (experiments 1, 4, 5, 6, 7); (b) the duration of the interstimulus interval ranging from -200 msec up to at least a second (experiments 2, 3, 5); and (c) the processing demands of the first task (experiment 7). It is suggested that the delay reflects a basic concurrence cost which remains when two reactions can be time-shared.     

Stimulus compatibility effects of an accessory visual stimulus on auditory sensitivity

Studies have reported that an accessory stimulus in a second modality can have a facilitative effect on sensory detection in a primary modality. However, performance declines when the subject has the additional task of reporting on the accessory stimulus. The facilitative effect has been attributed to an arousal or warning process, while the interference effect has been characterized as a result of limited channel capacity. Auditory sensitivity was assessed under accessory visual stimulation. Visual stimulus intensity (arousal), processing demand, and interstimulus compatibility (same or opposite direction of change of primary and secondary stimuli) were manipulated. The results indicated that interstimulus compatibility, not arousal, accounted for the obtained facilitation effect. Interference due to additional task demands was not observed. It was proposed that the facilitation effect was due to selective sensory encoding.     

Modulations of the processing of line discontinuities under selective attention conditions?

We examined whether the processing of discontinuities involved in figure-ground segmentation, like line ends, can be modulated under selective attention conditions. Subjects decided whether a gap in collinear or parallel lines was located to the right or left. Two stimuli were displayed in immediate succession. When the gaps were on the same side, reaction times (RTs) for the second stimulus increased when collinear lines followed parallel lines, or the reverse, but only when the two stimuli shared the same orientation and location. The effect did not depend on the global form of the stimuli or on the relative orientation of the gaps. A frame drawn around collinear elements affected the results, suggesting a crucial role of the "amodal" orthogonal lines produced when line ends are aligned. Including several gaps in the first stimulus also eliminated RT variations. By contrast, RT variations remained stable across several experimental blocks and were significant for interstimulus intervals from 50 to 600 msec between the two stimuli. These results are interpreted in terms of a modulation of the processing of line ends or the production of amodal lines, arising when attention is selectively drawn to a gap.     

Age related changes in the effectiveness of name and visual codes in recognition memory

In the first of three studies college, third grade, and kindergarten Ss were able to determine that two stimuli presented 700 msec apart were the same more quickly if they were visually identical than if they shared the same name. If 3000 msec elapsed between stimulus presentations third grade and college Ss responded at the same rate in making both types of matches, whereas kindergarten Ss appeared to continue to respond more quickly in making visual matches. Study II was an unsuccessful attempt to replicate the kindergarten finding. A warning signal, presented 500 msec prior to the second stimulus, reduced RTs at both interstimulus intervals, but no significant differences in making visual and name matches occurred. In Study III first-graders, responding either with or without a warning signal, were found to respond like the older Ss in Study I. The warning signal again reduced RT at both intervals. The results suggest that Ss across a wide age range are able to use the visual properties of a stimulus for only a very brief period as the basis for making matching judgments.     

Action planning during the presentation of stimulus sequences: Effects of compatible and incompatible stimuli

Experimental designs that require the simultaneous perception and reproduction of a stimulus sequence could help to clarify the relationship between perception and action. This contribution examines a specific stimulus-response compatibility with the reproduction of simple stimulus sequences. In the procedure a response just prepared or one to be prepared is confronted with a new incoming stimulus that is compatible or incompatible with the response. Interference is predicted from a framework in which stimulus perception and action control are assumed to share common codes.Five arrows were successively presented at 1-s intervals. The arrows pointed either to the left or to the right with equal probability. One of the five arrows was accompanied by a randomly presented go signal. Subjects then had to reproduce the sequence by pressing corresponding left or right keys while the stimulus presentation continued. Reaction-time latencies and reaction intervals within a sequence were analyzed in six experiments. Results showed increasing reaction-time latencies the later the go signal was presented — that is, the longer the sequence to be reproduced was. In contrast to previous findings, this effect interacted with the compatibility between the arrow displayed together with the go signal and the first reaction. It is argued that the go signal initiates a transfer of a cognitive action plan to a peripheral motor program and that this process is subject to interference the more the current stimulus is at odds with one of the first parameter specification.     

Rate changes after unscheduled omission and presentation of reinforcement

Changes in response rate similar to frustration effects were studied in a two-lever situation. Responding on one lever on a fixed-interval schedule produced access to water for 5 sec and an exteroceptive stimulus. In the presence of this stimulus, responding on another lever on a fixed-interval schedule produced access to water for 5 sec and terminated the stimulus. Occasional omission of a previously scheduled reinforcer after responding on the first lever resulted consistently in increases in rate on the second lever during the immediately succeeding interval. In another procedure, occasional presentation of a previously unscheduled reinforcer after responding on the first lever resulted consistently in decreases in rate on the second lever during the immediately succeeding interval. Changes occurred after the first omissions or presentations and were about the same in magnitude as the procedure continued over several sessions. Typically, an increase or decrease in rate was maintained throughout an entire 100-sec interval. Changes in rate on the second lever of approximately the same magnitude also occurred when rate on the first lever was near-zero under a schedule that differentially reinforced behavior other than lever pressing.     

Recovery cycle of the evoked heart rate response in sleeping humans

Paired auditory stimuli, presented during sleep, evoked biphasic heart rate responses of greater than 10-second duration. The magnitude of the response to a second stimulus varies with the time between stimuli. The recovery cycle for human subjects exhibits a subnormal period for both HR peak and trough components at 5-or 6-second interstimulus intervals, and a supernormal period for the HR peak at 9-or 10-second interstimulus intervals. Thus, subnormal and supernormal periods coincide with the peak and trough, respectively, of the biphasic evoked heart rate response.     

Successive matching-to-sample in the pigeon: Variations on a theme by Konorski

In 1959, Konorski proposed a successive matching-to-sample paradigm with which to study short-term memory in animals. Although the technique has been little used, it affords several distinct advantages over more commonly employed matching-to-sample procedures. Konorski’s paradigm involves the successive presentation of a pair of discriminative stimuli with a brief interstimulus interval between them. Reinforcement is scheduled to occur only when the second stimulus of a pair matches the first; otherwise, nonreinforcement follows. An investigation of the pigeon’s food-reinforced keypecking behavior is reported using a variant of Konorski’s technique. Pigeons rapidly learned to differentiate matching and nonmatching stimulus pairs when brief (5-sec) color stimuli were separated by a 1-sec interstimulus interval. No such differentiation arose when control subjects were trained with reinforcement equiprobable on matching and nonmatching trials. No support was found for the notion that correct performance under this successive-matching procedure was due to overt mediating behaviors.     

Parallel processing and the psychological refractory period

The serial processor theory proposed by Welford is the traditional explanation of the delay in responding to the second stimulus presented in psychological refractory period paradigm experiments. This paper reviews results which do not accord either with that theory or with later modifications of it by Smith and Tolkmitt. To explain these results a model is proposed which contains three propositions: (a) parallel processing of concurrent stimuli, (b) fixed total processing capacity, (c) capacity allocation either dependent on the relative difficulty of the stimuli or set by the subject according to experimental instructions. The predictions of this model for the effects of stimulus difficulty and interstimulus interval on reaction time and interresponse interval are computed. These predictions are compared with those of other parallel processing models of the psychological refractory period which have been proposed by Herman and Kantowitz, by Kahneman and by Keele.     

The effect of temporal distribution in relation to constant frequency of stimuli on habituation of the orienting reaction

The lack of empirical evidence for faster habituation with the regular presentation of stimuli suggests that it is not the constancy of presentation of stimuli, but rather the rate of stimulation--defined as the reciprocal of the harmonic mean of the interstimulus intervals--that determines the speed of habituation. Using alternation of 10-70 and 30-50 sec and a constant sequence of 40 sec, three different rates of stimulation were realized. The hypothesis of faster habituation of skin conductance reactions with higher rates of stimulation was not confirmed. However, a consistent pattern of skin conductance reactions, with an increase in reaction after long intervals and a decrease after short intervals, was found, especially in the group with alternating intervals of 10 and 70 sec. The analysis of an additional group with a random sequence of intervals showed that the response pattern did not result simply from the expired time since last stimulus, i.e., a simple mechanical effect. The possibility of anticipating the stimuli and differing information content of the stimuli are discussed as possible determining factors.     

Non-aging fore-periods and simple reaction time

This study deals with the relationship between the momentary objective probability of the delivery of a stimulus and the reaction time in a simple reaction-time task. The hypothesis was that the reaction time is closely related to the objective probability via expectancy i.e., the momentary probability of the delivery of the stimulus as experienced by the subject. This problem was experimentally approached from two directions: (1) by varying the objective probability, in which case the reaction times should change inversely with the objective probability, and (2) by keeping the objective probability constant (by using the Bernoulli process), in which case the reaction times should not change. Eight male subjects were used. The first assumption proved to be correct, whereas the second held only when certain mean inter-stimulus intervals were used.     

Reduction of the “psychological refractory period”

The usual increase in reaction time which occurs when a reaction stimulus is preceded by one irrelevant stimulus was-reduced 30% by preceding the latter with a second irrelevant stimulus at certain critical intervals between stimuli. The interaction between the irrelevant stimuli, as measured by reaction time, has a different time course than the interaction implicit in tlte “psychological refractory period”.