Refractoriness of on Extended Movement to Directional Change

An extended movement was used to compare the memory-drum and single-channel definitions of psychological refractoriness. The basic movement In response to the first signal (S₁) was a forward lunge and a concurrent arm swing through a target string. The response to the second signal (S₂) was a reversal of the original movement The interstimulus Interval (ISI) ranged from .10 – .70 sec. in .10-sec. steps. The hypothesis that refractoriness of the reversal movement would decrease as ISI shortened was confirmed by the fact that error frequencies decreased significantly and substantially with decreasing IS I. The availability of some residual capacity to deal with S₂ during the refractory period was also indicated by an examination of the relationship between RT₂ and the interval between S₂ and RT₁. This departure from the classical single-channel model shows some agreement with the neuromotor-programming theory.     

Intersensory effects in the psychological refractory period

Two experiments examined reaction time (RT) to each of two stimulus events separated by short interstimulus intervals (1SI). The essential contrast was RT to the second visual signal, RT₂, in auditory-visual (A-V) vs visual-visual (V-V) sequences. With response, certain pairings in Experiment 1, an effect apparently demonstrating a single-channel process (Welford, 1952), was noted. RT₂ was generally faster for A-V as opposed to V-V sequences especially when Ss were uncertain as to the sequence that would occur. At 0-msec ISI, the RT₂ difference between sequences approached the RT! difference. More rapid RT₂ to A-V sequences was also observed with go vs no-go pairings in Experiment 2 when the initial event was a go signal. However, the RT difference disappeared upon error correction, making the RT₂ sequence difference of questionable relevance to the hypothetical single-channel process. RT₂ was more rapid following a null no-go signal when the no-go signal was contrasted with a visual as opposed to auditory go signal. The latter effect was independent of error and is consistent with channel-switching theory (Kristofferson, 1967).     

Effects of time and event uncertainty upon sequential information processing

Two experiments were conducted to investigate the psychological refractory period (PRP), a delay induced into the second of two reaction times (RT) when the interstimulus interval (ISI) is short. In Experiment1, time and event uncertainty were factorially varied by providing or not providing S with foreknowledge of the ISI and the order in which the two events would occur, respectively. ISIs of0, 50, 100, 200, and400 msec were used. Time and event uncertainty produced independent degradation of both RTs. Also, the second RT (RT ₂ ) was delayed at50 msec ISI when both time and event certainty were present. Experiment 2 attempted to replicate this latter finding using ISIs of0, 25, 50, 75, and100 msec. Delays in RT ₂ were found for the middle three values of ISI. These results were interpreted as supporting a modified single channel theory of the PRP.     

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.     

Concomitant short-term changes in the auditory evoked response, the EEG, and reaction-time performance in relation to the temporal parameters of stimulation

Abstract.— Two experiments are described in which short-term "habituation" of the auditory evoked response (AER) was examined using discrete trains of click stimuli and averaging across trains. In the first study, the stimuli consisted of randomly interspersed trains of regular clicks, at 3 or 10 sec interstimulus interval (ISI). In the second study, the ISIs were also short or long but were irregular varying between 2.4 and 3.6 sec in the former case and 6 to 12 sec in the latter. The N₁-P₂ component of the AER diminished within the 3 sec trains especially for the regular stimulation; no such development occurred with the longer ISI. The total voltage in the background EEG and the reaction-times to the stimuli showed essentially similar changes. The possible mechanisms governing the response decrement are discussed and it is concluded that the data may be interpreted in terms of the Groves and Thompson dual-process theory of habituation.     

Hick’s law equivalent for reaction time to individual stimuli

Hick’s law, one of the few law-like relationships involving human performance, expresses choice reaction time as a linear function of the mutual information between the stimulus and response events. However, since this law was first proposed in 1952, its validity has been challenged by the fact that it only holds for the overall reaction time (RT) across all the stimuli, and does not hold for the reaction time (RT_i) for each individual stimulus. This paper introduces a new formulation in which RT_i is a linear function of (1) the mutual information between the event that stimulus i occurs and the set of all potential response events and (2) the overall mutual information for all stimuli and responses. Then Hick’s law for RT follows as the weighted mean of each side of the RT_i equation using the stimulus probabilities as the weights. The new RT_i equation incorporates the important speed–accuracy trade-off characteristic. When the performance is error-free, RT_i becomes a linear function of two entropies as measures of stimulus uncertainty or unexpectancy. Reanalysis of empirical data from a variety of sources provide support for the new law-like relationship.     

Signal recognition models compared for random and Markov presentation sequences

Models of two-category signal recognition are compared to data from a variety of experimental conditions. For recognition, one of two signals (S₁, S₂) which vary slightly on some simple physical dimension is presented on each trial, and 0 is to identify (I₁, I₂ ) which signal was presented. In general, Os show a decrease in both Pr(I₁ /S₂) and Pr(I₂/S₁) for either greater Pr(S₂) or, sequentially, for greater S₂ recency. These effects are described as probability and sequential contrast, respectively. The memory state model (MS) describes a three-state threshold process with responses determined by a simple first-order Markov process which depends on the sensory state and response on the immediately preceding trial. The memory trace regression model (MTR) assumes that O compares the observed signal event with the memory trace of the previous signal event. When the difference is large, the sign of the difference determines the response; when it is small, the response depends on the preceding response. The memory trace is assumed to regress toward the mean signal value. Both models accurately predict the observed bias changes as a function of signal probabilities and of the subsequence of events on the previous trial. The response axioms of the MTR model are modified to predict the results for individual Os for Markov chains of signal events. The response axioms of the MS model are modified to predict responding when information is given to O concerning signal probabilities. Although both models do well under all conditions, the MS model uses fewer parameters and correctly predicts the direction of higher order sequential dependencies.     

Delayed alternation in the pigeon

Pigeons were studied in a delayed-response task requiring alternation of key pecks on two response keys. Blackouts of from 1 to 10 sec intervened between successive choices on the two keys.

The following results were obtained: (1) Birds performed at well above chance accuracy on all the delays tested. Accuracy was generally lowest at 1- and 10-sec delays. (2) Overt postural orientations during the delay interval appeared to mediate accurate key-pecking behavior. (3) The shape of the delay vs. accuracy function was discussed in terms of the possibly confounding influences of (a) stimulus “trace” variables, and (b) aversive effects of the time outs produced by incorrect responding.

     

Slow potential changes and choice reaction time as a function of interstimulus interval

Slow potential changes were recorded over the vertex (C_z) during a choice reaction task. The constant interstimulus interval (ISI) between the visual warning (S₁) and the visual imperative signal (S₂) was either 200, 400, 1000 or 2000 msec. The contingent negative variation (CNV) was not only measured between S₁ and S₂ (CNV₂), but also before S₁ (CNV₁).The main results were: (1) The CNV₂ amplitude showed significant variation as a function of ISI. It reached its maximum with an ISI of 1000 msec. (2) CNV₁ developed only before the short ISIs (200 and 400 msec). (3) When CNV₁ and CNV₂ were summed the differences in CNV amplitudes and durations between different ISIs became smaller. (4) The peak-to-peak amplitude P₁-N₁ of the potential evoked by S₁ was enhanced with short ISIs. (5) The correlations between mean CNV and median reaction time (RT) were low but significant for ISIs of 400, 1000 and 2000 msec. When, however, the effect of subjects was partialized out these correlations were drastically reduced, whereas the partialization of session and block effects had no noticeable influence on these correlations. (6) The correlations between single RT and single CNV (measured for the ISI of 1000 msec, individually for two subjects) were weak or even completely lacking.The main conclusion was that CNV coincides with preparedness to react to a stimulus in a choice RT-task, but its amplitude at the moment of onset of the imperative stimulus does not reflect, or reflects weakly, the degree of preparedness (as indicated by RTs) at that moment.     

Delayed escape from light by the albino rat

Two albino rats were trained to terminate an aversive light for 1 min by pressing a bar. After 19 hr of conditioning they were exposed to successive delays of 1, 2, 5, and 10 sec imposed between occurrence of the escape response and light termination. No stimulus change accompanied the delay interval, and any additional responses made at this time reset the delay timer. For both rats the relative frequency of escape responses with very long latencies increased as the delay interval increased. The modal escape latency, however, remained essentially unchanged for all delay values of greater than 1 sec. “Superstitious” responding was observed during the delay interval.     

Effects of a delay-reinforcement procedure on performance under IRT>t schedules

Water-deprived rats were studied under a compound schedule that prescribed that responses terminating interresponse times (IRTs) greater than a fixed value t₁ (IRT > t₁ component schedule) initiated a delay of reinforcement interval t₂, at the end of which water was presented if the subject did not respond ( > t₂ component schedule). If the subject responded before the t₂ interval elapsed, the IRT > t₁ component schedule was re-initiated and water was not presented. The IRT > t₁ and > t₂ component schedules were not differentially correlated with distinctive stimuli. Rate of responding during the IRT > t₁ component decreased as a function of the value of t₂. The magnitude of the decreases in response rate appeared to be proportional to the subject's rate under the IRT > t schedule with no delay of reinforcement (t₂ = 0 sec). The effects were independent of the parameter value of the IRT > t₁ component schedule and of the rate of reinforcement. The results suggested that “efficiency” of performance under IRT > t schedules can be increased by appropriately arranging brief delays of reinforcement.     

Two-phase model analysis of the effects of interstimulus interval and masking task in human aversive classical conditioning

Three levels (.5, 1.0, and 2.0 sec) of interstimulus interval (ISI) and presence vs absence of a masking task were manipulated in a human eyelid reflex conditioning situation. Through the use of a two-phase model of conditioning performance, it was concluded that (1) increasing the ISI and introducing a masking task increased the duration of Phase 1, (2) as ISI increased, the amount of conditioning decreased, (3) the trial-by-trial rate of change in response probability increased as a function of ISI, and (4) the masking task reduced operator limits. It was also noted that the typical ISI function is composed of rate effects at short ISis and conditioning limit effects at long ISIs and that the larger 0 at larger ISis does not follow from a model of the stimulus trace hypothesis.     

Preference for mixed versus constant delay of reinforcement

Preference for constant and mixed delay of reinforcement was studied using concurrent equal variable-interval schedules. For four pigeons, pecking one key was reinforced following constant delays of 8 sec and mixed delays of 6 or 10 and 2 or 14 sec. Pecking a second key was reinforced following constant delays of 0, 8, 16, and 32 sec. For two additional pigeons, pecking one key was reinforced following delays of 30, 15 or 45, 5 or 55, and 0 or 60 sec. Reinforcements on the other key were delayed 30 sec. It was found that (a) pigeons preferred mixed relative to constant delay of reinforcement, and (b) preference for mixed delay of reinforcement increased as the range of delay interval variability increased.     

Long delay learning in the T-maze

Rats were trained to go to one side of a T-maze with delays of reward lasting 1, 20, or 60 min in Expt 1 and 1 or 60 min in Expt 2. Mediation by secondary reward was prevented by administering the same delay treatment regardless of whether the response was correct or incorrect: after a response, the rat was removed from the choice alley and placed in its home cage to spend the delay. Feedback for the response was given in the startbox after the delay interval ended. The rats learned and there were no significant differences in performance among groups trained with different delays. These results had been expected on the basis of Revusky's (1971) hypothesis that removal of the rat from the learning situation to spend the delay elsewhere facilitates long delay learning by reducing associative interference. In Expt 3, this notion was tested explicitly by varying the amount of a 2-min delay to be spent in the experimental situation. Different groups of rats were left in the choice alley after the response for 0, 15, or 60 sec; then the rats were removed to spend the remainder of the 2-min delay in the home cage As predicted, the level of performance decreased as the length of time in the choice alley was increased.     

Concurrent-chain performance in transition: effects of terminal-link duration and individual reinforcers

Pigeons responded on concurrent-chain schedules with variable-interval initial links and equal delays as terminal links. The terminal-link delays were 1 sec in some conditions and 20 sec in other conditions. The percentages of reinforcers delivered for responses on the left key were 10%, 30%, 70%, or 90%, and this percentage was switched every five to nine sessions. The rate of change in the pigeons' response percentages after a switch was the same whether the terminal-link delays were 1 sec or 20 sec. Analysis of the effects of individual reinforcers showed that after a response on one key had been reinforced, response percentages on that key were higher for at least the next 100 responses. Small effects of individual reinforcers were evident after eight or nine additional reinforcers had been delivered. The effects of individual reinforcers were about equally large during times of transition and during periods in which overall response percentages were relatively stable.     

Processing of geometrical dimensions in a binary classification task: Evidence for a dual process model

Confirming the findings in search tasks with letters and digits, the typical RT_same < RT_diff result was obtained in a matching paradigm requiring the classification of geometrical stimuli that were given in pairs. The study supports a dual process model that is based on an identity reporter for the faster “same” response and a difference detector for the slower “different” responses, both operating with equal accuracy. Subjects appeared to perceive outline aspects of figures, formed by size and form, holistically. An internal characteristic, such as an interior line, was apparently processed as a separate attribute. However, the outlines of the stimulus configurations appeared to be much more salient and interfered with the judgment of the orientation of the interior line. Moreover, the latter stimulus aspect could be easily ignored as the task required.     

The basic parameters of human information processing: Their role in the determination of intelligence

Information psychology deals with information processing in humans which is measured in terms of time units (sec) and information units (bits) and is described by relatively simple models. The model of psychostructure is crucial. It adequately refers to information processing which runs as sequential dichotomous decisions on a ‘yes-no’ or an ‘on-off’ basis. The information unit 1 bit is allocated to each decision.Three basic parameters are important in central information processing: (1) The information flow to the short term storage C_K (15.0 ± 3.1 bit/sec in adults). (2) The duration of presence (retention in primary memory) = T_R (5.4 ± 0.8 sec in adults). (3) The basic speed of learning C_V (depending on the time to retrieval: 0.01 to 1.00 bit/sec in adults). These capacities increase continuously from childhood to adulthood. Within each age group there are remarkable individual differences which exceed variations of biological variables such as body length or brain weight by far.The prerequisite of information psychological measurement is to determine the information content of the stimuli and the reactions and to measure the time between the stimulus and the response. Based on this it is shown that the basic parameters are unspecific, because the type of information, the sensory modalities and the repertory of signs do not alter the results. Besides, the parameters are independent of each other and reach the level of a ratio scale. According to other concepts and other empirical findings, C_K and T_R determine the intelligence quotient including the vocabulary while C_V corresponds to mechanical learning. Tests for these parameters are given.     

Memory for sequences of stimuli and responses

Two experiments sought to determine if pigeons could discriminate and remember recent sequences of stimuli and responses. A variant of Konorski's short-term memory procedure involving successive presentation of sample and test stimuli was used. The samples were stimulus-response pairs of the form, (S-R)₁–(S-R)₂. Differential test responding disclosed memory of the two-item samples, with birds showing earlier and greater control by the second item than the first (Experiment 1). When the retention interval separating the second item of the sample sequence from the test stimulus was lenghtened from .5 to 2.0 or 4.0 sec, a systematic loss of stimulus control resulted; however, when varied over the same temporal range, the interval between the two items of the sample sequence had a much smaller effect, or none at all (Experiment 2). These results support an account of response-sequence differentiation that stresses short-term memory of organized behavior patterns.     

EFFECTS OF INTERSTIMULUS INTERVAL AND PREDICTABILITY OF EVENT STRUCTURE ON SERIAL REACTION TIME

A mean interstimulus interval (ISI) of 10 sec. resulted in significantly-shorter RTs to a single light stimulus than a 30 sec. average ISI. During a second workperiod the groups performing under each of the two ISI conditions were divided into four subgroups given 0, 25, 50 or 75% interspersion of an additional stimulus (sound). With short ISIs the condition of maximum predictability of event structure (light stimulus only) gave the shortest average RTs. With lessened predictability (increased proportion of the sound stimulus) there was a slight monotonous increase in RT. With long ISIs the same relationship was curvilinear, i.e. 25% interspersion of sound stimulus was most effective in preserving vigilance.     

A discrete time model for detection of randomly presented stimuli

Considered in this paper is a discrete-time Markov decision process with unobservable states, which occurs in equipment checking, medical diagnosis, signal detection, and reaction time studies. The process is characterized by (i) a state S₀ that at some unknown time t, which is determined probabilistically, turns into an absorbing state S₁; (ii) observations that provide fallible information about the true state and which are taken sequentially to determine whether or not the change from S₀ to S₁ has occurred; and (iii) losses for a false alarm and for delays in detecting the change. A response model is proposed, prescribing a terminal decision as soon as the posterior probability that S₁ obtains reaches or exceeds a fixed probability boundary. Predictions are derived concerning the probability of false alarm and several conditional distributions of the number of observations taken.