Confidence ill stimulus predictions and choice reaction time

In two choice reaction time (RT) experiments, a stimulus prediction and a confidence judgment in the prediction preceded each occurrence of one of two stimulus alternatives. Ss identified each stimulus presentation by pressing a left-hand or right-hand telegraph key. In Experiment I the source of the stimulus predictions and confidence estimates was varied between groups of 20 Ss. For each condition, RT to correctly predicted stimuli was an inverse function of prediction confidence. Following incorrectly predicted stimuli, RT was not reliably influenced by confidence when S gave both predictions and confidence judgments; but RT to incorrectly predicted stimuli was an increasing function of confidence when E verbalized the predictions and confidence estimates or when S predicted and E indicated confidence. In Experiment II Ss made predictions and the validity of Es confidence estimate was manipulated between Ss. When Es confidence was perfectly related to the probability of a correct prediction, choice RT to nonpredicted stimuli was inversely related to confidence. However, choice RT to nonpredicted stimuli was not affected by prediction confidence when Es judgments were random.     

Detection of change in nonstationary binary sequences

The present study was designed to investigate the ability of humans to detect changes in the underlying probability structure of binary sequences of events. Four Ss were presented with sequences of 30 events (zeros and ones) which had been generated by two underlying probability values. P₁ was the probability of a one in the first i events, P₂ was the probability of a one in the last 30-i events, and the distribution of i was uniform from 1 to 29. The Ss indicated, without feedback, where the transition point from P₁ to P₂ took place for four sets of problems in which P₁ and P₂ took on the following pairs of values: (.40, .60), (.20, .80), (.05, .60), and (.50, 1.00). Estimates by Ss were compared with true transition points, i, and with maximum likelihood estimates of i. The difference between P₁ and P₂ and the closeness of at least one P value to the boundaries, either zero or unity, interacted in determining the difficulty of the problem for Ss.     

Prediction outcome probabilities as determinants of choice reaction time

In a two-stimulus two-response choice reaction time (RT) task in which Ss made stimulus predictions, the probability of a correct prediction was manipulated between Ss. The magnitude of the difference in RT to correctly and incorrectly predicted stimuli (i.e., the prediction outcome effect) was an increasing function of the probability of a correct prediction This finding was primarily due to a reliable decrease in RT to correctly predicted stimuli as the probability of a correct prediction increased, since RT to incorrectly predicted stimuli was not affected by prediction outcome probability. These results were interpreted as partially supporting a continuous expectancy notion which involves facilitory and inhibitory mechanisms winch are differentially influenced by the probability of a correct prediction.     

Reaction times for a same-different discrimination of vowel-consonant syllables

Reaction times (RTs) were measured for decisions in a same-different discrimination of successive vowel-consonant nonsense syllables. Averaged data showed that “same” RTs were faster than “different” RTs and that the “different” RT decreased as the number of features (Wickelgren, 1966) by which a pair contrasted increased. For individual phonemic comparisons, two of the dependent variables, P(S I d), or probability of responding “same” to a different trial and the mean correct “different” RT, were related in that the RT increased as P(S I d) increased. The size of the difference between “same” and “different” RTs for a given phonemic contrast was directly related to P(S | d). The difficulty of a comparison, as described by P(S I d) and by the difference between correct “same” and “different” RTs, was explained through a markedness classification of phonemes.     

Set and temporal integration

An experiment was conducted to explore the temporal structure of set formation in a complex reaction time (RT) task. On each trial an instruction [I-event] was given telling Ss whether identity of color or form on a separately presented alternative display (A-event) was the dimension relevant on that trial. The A-event consisted of a pattern of four colored forms. The two forms on one side were matched for color and on the other side for form. S’s task was to depress one of two keys. The correct key was homolateral to the matched relevant dimension. The basic independent variable was the time interval separating the I- and A-events (ISI). At short ISIs, RT wasa linear function oflSI with slope equal to -0.5. RT was independent of the order in which the events occurred at short ISIs, although at longer ISIs (3 sec) RT was longer when the A-event followed the I-event. Also, RT was shorter at short ISIs when color was the relevant dimension rather than form. although this difference disappearedat longer ISIs. The results were discussed in relation to information processing models and previous research dealing with partialadvance information.     

Reaction time as a function of the intensity and probability of occurrence of vibrotactile signals

Three Ss made judgments of the presence or absence of a burst of 60-cps vibration onthe index fingertip.The probability of S’s reporting the presence of a signal was found to be influenced by signal probability and signal intensity. Mean reaction time for reporting the presence of a signal decreased as a function of signal intensity and signal probability whereas mean reaction time for reporting the absence of a signal increased as a function of signal intensity and signal probability. On trials where no signal was presented mean R T for reporting a signal decreased with increases in the signal probability whereas mean RT for reporting the absence of a signal increased with increases in signal probability. The results were interpreted as support for the hypothesis that S’s decision time was longer the closer on the sensory continuum a particular observation was to his criterion.     

Visual stimulus intensity and location probability: Interactive effects on choice reaction time

Three prevalent models predict different stimulus intensity effects on RT. These are: the serial-stage model (additivity), the variable criterion model (larger intensity effects with slower responding), and the temporal overlap model (smaller intensity effects with slower responding). The predictions were tested in a dual-response situation including oculomotor and manual responses (RT). Other variables were stimulus location probability (expectancy), foreperiod (alertness), and stimulus intensity (encoding. In Experiment I, an Intensity x Probability interaction was found such that the intensity-effect was smaller at low stimulus probability. Three further experiments were performed in order to specify some of the conditions relevant for this phenomenon. The results are consistent with the temporal-overlap interpretation. It was suggested that the obtained interaction results from a processing delay due to increased demands for cognitive and response processing (Stanovich & Pachella, 1977), or to the attention switch to an unexpected S-R event.     

Response Speed and Accuracy During Anticipatory Stress

Response speed and accuracy of 48 general aviation pilots were determined under condition of anticipatory physical threat stress (APTS). Variables included unpleasantness of the event (electrical shock), proximity of the event, and relationship of Ss’ performance to the occurrence of the event. The data support inclusion of these variables in Wherry’s model of APTS. Ss who believed they could avoid the shock by an adequate performance were able to maintain or improve that performance while the performance of Ss who perceived the shock as inevitable was deteriorating. Two possible modifications of the APTS model were discussed: (1) weighting APTS determiners according to their effectiveness in generating anticipatory stress, (2) recognizing the interaction of the APTS variables with S’s personality structure.     

Effects of noise letters upon the identification of a target letter in a nonsearch task

During a 1-sec tachistoscopic exposure, Ss responded with a right or left leverpress to a single target letter from the sets H and K or S and C. The target always appeared directly above the fixation cross. Experimentally varied were the types of noise letters (response compatible or incompatible) flanking the target and the spacing between the letters in the display. In all noise conditions, reaction time (RT) decreased as between-letter spacing increased. However, noise letters of the opposite response set were found to impair RT significantly more than same response set noise, while mixed noise letters belonging to neither set but having set-related features produced intermediate impairment. Differences between two target-alone control conditions, one presented intermixed with noise-condition trials and one presented separately in blocks, gave evidence of a preparatory set on the part of Ss to inhibit responses to the noise letters. It was concluded that S cannot prevent processing of noise letters occurring within about 1 deg of the target due to the nature of processing channel capacity and must inhibit his response until he is able to discriminate exactly which letter is in the target position. This discrimination is more difficult and time consuming at closer spacings, and inhibition is more difficult when noise letters indicate the opposite response from the targe     

High order sequential effects and the negative gradient of the relationship between simple reaction-time and foreperiod duration.

In a simple RT task with variable interstimuli intervals (ISI), the negative slope of the RT-ISI duration relationship is generally interpreted as an effect of the increasing conditional probability of the response signal (RS). A previous study using 6 different ISIs has shown that the first order sequential effects (SE) contribute, for a part, to this slope. The aim of the present experiment was to investigate, up to the fifth order, the SEs observed when two different ISIs (1.5 and 3.0 sec) are used. The results show that SEs also intervene in the tendency for the Ss to be preferentially prepared when the RS occurs at the end of the long ISIs. They are discussed according to the hypothesis that the role played by these SEs in the negative slope of the RT-ISI relationship is primarily due to the opportunity given the Ss in such an experiment to make two successive preparations.     

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).     

The effect of memory load on reaction time in character classification

In order to investigate the effect of memory load on reaction time (RT), choice RT trials were embedded in a binary character classification task using the varied set procedure. Twelve Ss performed in experimental blocks, as well as in control blocks consisting of character classification trials only. In experimental blocks, every trial began as a classification trial with the presentation of a new positive set. On a random half of these trials, however, a choice RT stimulus was presented instead of a probe letter and S simply made the indicated response. Results indicated that memory load had no effect on the choice RT trials. Embedding choice RT trials in the classification task affected the intercept (but not the slope) of the function relating classification RT to memory load. This result implies that the increase in latency usually obtained in classification experiments is entirely due to an increase in the duration of the memory searching stage of processing.     

Transformations on sets in short-term memory: Temporal and spatial factors influencing deletion

An individual’s ability to perform a deletion operation on sets in short-term memory was explored in a reaction time (RT) experiment. Special attention was given to the importance, for deletion, of temporal and spatial variables. Ss did perform a deletion operation. The speed of correct recognition was influenced by both the delay between the deletion (D) set and a test item and the serial order correspondence between identical items in the to-be-remembered or positive (P) set and the D set.     

Some Comments on the Methodological Significance of the Definition of a Response

Evidence in the present study, in conjunction with evidence in previous studies, indicates that sensory or perceptual factors do not account for the slowing that occurs in later life. Elderly Ss are slower than young adult Ss, but, up to the point of fairly weak stimulation (55 db), they are as slow in relation to auditory stimuli that are loud and easy to perceive as they are to stimuli more difficult to perceive. An unanticipated interaction involving stimulus intensity was observed which warrants further attention. When, in the course of the study, the intensity of stimulation was systematically decreased, reaction times (RTs) of older Ss with a .5 second preparatory interval (PI) were much slower than when the intensity of stimulation was systematically increased.

An exploratory study was also carried out. In this study, the pacing of stimulus events was predictable, and Ss were instructed to take advantage of this. RTs were quicker with this procedure than with traditional RT procedures, but not significantly more for old adult Ss than for younger ones. However, the level of significance was such as to suggest that timing may be an important clue to the slowing in later life.     

Probability effects in choice reaction time tasks

This paper contains a short review of the main results that were obtained by the author in a series of experiments that constituted a study of the effects of signal probability on choice reaction time. The effects of stimulus probability are shown to be influenced by the following variables: (1) differences in the method of varying stimulus probability, (2) differences in task complexity, (3) differences in S-R code, and (4) differences in Ss’ motivation. The data that are considered here are the overall mean RT for particular signals and the mean RT for sequential repetitions. Two questions, related to the psychological “nature” of the probability effects in choice RT are discussed: (1) The question of the relationship between the relative frequency and the number of alternatives as two different ways of determining the probability effect in choice RT; and (2) the question of identifying the main determinants of the trial-to-trial variability of RT in such experiments.

     

Differential effects of voluntary expectancies on reaction times and event-related potentials: evidence for automatic and controlled expectancies.

Expectancy has been used to explain the effects of stimulus sequences both on reaction times (RTs) and on the P300 component of the human event-related potential. However, there are conflicting views about the control obtainable over these underlying expectancies. We compared the effects of voluntary expectancies for stimulus changes or repetitions in random tone series on RTs and the P300. Ss responded according to either stimulus identity (Experiment 1) or stimulus sequence (Experiment 2). In both experiments RTs were strongly affected by event expectedness. P300 amplitude, on the other hand, was affected (as a trend) only in Experiment 2. The results suggest that there are at least 2 types of "expectancy", one that is largely automatic and inflexible, reflected in P300 amplitude, and a second, controlled process that is reflected mainly in RT. The latter type of expectancy appears to affect processing stages beyond stimulus evaluation and classification.     

The remembering of auditory event durations.

Three experiments examined the incidental remembering of event durations. In each study, Ss engaged in an initial learning phase in which they performed a set of perceptual ratings on events for a varying number of trials. These events consisted of tonal sequences or ecological sounds that varied in their internal structure and ending. Ss were then given a surprise memory task in which they were asked to recognize the duration of each event (Experiments 1 and 3) or extrapolate its completion (Experiment 2). Results showed that in contrast to irregularly timed events, those filled with regularly timed or continuous pitch information yielded high levels of accuracy that increased with greater learning experience. In addition, durations marked by a nonarbitrary ending were more accurately remembered than those marked by an arbitrary ending which, in fact, were misremembered as shorter than their actual duration. These findings are discussed in terms of an approach that emphasizes the role of event structure on perceiving and remembering activities.     

主体关联性对贝叶斯推理概率估计的影响

用贝叶斯推理问题为实验材料,探讨了主体关联性对贝叶斯推理概率估计的影响。结果表明,当估计的事件与主体有关时,被试对消极事件概率估计较低,对积极事件概率估计值;当估计的事件与主体无关时,被试对消极事件和积极事件的概率估计无显著差异。反应时分析表明,被试对消极事件的概率估计比对积极事件的概率估计时间显著地长,当消极事件与主体有关时概率估计时间就更长;而对积极事件的概率估计,与主体有关和与主体无关时反应时差异不显著。这表明,被试对消极事件的概率估计(特别是消极事件与己有关时)更为慎重。     

High-speed memory retrieval with auditorily presented stimuli

Two groups of 8 Ss memorized three lists of consonental phonemes. The length of the memorized lists (M) was one, two, and four phonemes. Test words were presented, and reaction time (RT) for S to say whether or not the word started with a member of the memorized list was measured. RT increased with M. In one group, the phonemes comprising the memorized sets were dissimilar. RT increased linearly with M for that group. In the other group, the phonemes comprising the sets were similar. The function relating RT to M appeared to deviate from linearity. Even after extended practice, all the evidence was consistent with a somewhat modified serial model of memory retrieval.