Parallel processing of the attributes of single stimuli

Three experiments are described, in which Ss had to decide whether or not single stimuli, varying along the dimensions of shape and color, satisfied a given criterion. In different conditions, the number of dimensions relevant to the criterion was varied. The first experiment indicates that simple interpretations of a standard Nickerson procedure are potentially artifactual. In the last two experiments, a design involving different difficulties of discrimination was used so that a serial interpretation of the results could be convincingly rejected, even for unpracticed Ss. These results strongly support the view that perceptually parallel processing normally occurs in the identification of single multidimensional stimuli. By this interpretation, apparently similar tasks may produce different patterns of results because of the use of different decision processes by the Ss.     

A comparison of auditory monitoring performance in blind subjects with that of sighted subjects in light and dark

Two experiments were performed in which blind Ss, sighted Ss working in the dark, and sighted Ss working in the light were compared as to their efficiency on an auditory watchkeeping task. Absolute and differential auditory thresholds were measured in both experiments, and in the second experiment the groups also underwent a signal detection session under alerted conditions. There was some inconsistency as to relative performance of the sighted groups, but in both experiments the blind Ss were superior on the auditory watchkeeping task as to signals detected and effective sensitivity (d’). 1 This difference was not attributable to a difference in auditory sensitivity or to a criterion adopted for     

Dissociation between Categorical and Coordinate Spatial Computations: Modulation by Cerebral Hemispheres, Task Properties, Mode of Response, and Age

Kosslyn suggested a dissociation of two kinds of spatial representations: categorical and coordinate, the former computed by the left hemisphere and the latter by the right hemisphere. In addition, with practice, a “categorization” of the coordinate computation would appear. These suggestions resulted largely from an experiment, replicated by others, in which the subjects had to estimate the relative position of a dot and a line by giving an oral response, and feedback was provided. The present series of five experiments was an attempt to test whether this finding could be generalized, under several methodological manipulations, some of which have already been used by researchers in separate studies. In the five experiments, accuracy was a more contributive dependent variable than correct latencies, and practice effects on the task × field interaction were not verified. Experiments 1–3 concerned the kind of response. When a manual instead of an oral response was required (Experiment 1;n= 32 Ss), the expected dissociation was observed (as well as when the latency of responses made by the right hand were studied). When the number of oral responses was increased from two (a binary choice) to eight, the dissociation was still observed for accuracy but disappeared when a more liberal criterion of accuracy was used to reduce the considerable task effect (Experiment 2;n= 32 Ss), or when response requirements were equated for both tasks (Experiment 3;n= 32 Ss). In Experiment 4 (n= 32 Ss), a manual response was called but the feedback was removed and the task dissociation disappeared. Finally, the task dissociation observed in Experiment 1 was not verified when a sample of elderly subjects was enrolled (Experiment 5;n= 32 Ss). However, age per se was the source of an interesting additional dissociation since only the coordinate computation was age sensitive. Our results suggest that the dissociation proposed by Kosslyn between the computation of categorical vs coordinate spatial relationships is highly unstable and sensitive to subtle methodological factors (vocal vs manual response, presence vs absence of feedback, binary vs “continous” response, age) which could preclude its general application.     

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).     

Response latency,confidence, and ROCs in auditory signal detection

Response latencies were obtained from 10 Ss in auditory signal-detection experiments. The response latencies were inversely related to certainty that a signal was (or was not) presented. The S’s decision criterion was found to have an influence on response latency, which was consistent with the hypothesis that stimuli close to the current criterion elicit longer response latencies than stimuli more distant from the criterion. Comparisons among receiver operating characteristics derived from binary decisions, from the latencies of binary decisions, and from confidence ratings show that response latencies and binary decisions together yield more information about the stimulus than does the binary decision alone. However, the increment in information gained from the measurement of response latencies is in general (though not for every S) smaller than that gained by shifting from yes-no responses to a confidence-rating procedure.     

The effects of anchoring and practice n the learning of bidimensional vibrotactile signals

Two groups of Ss were required to make judgments of bidimensional vibrotactile signals over a period of five weeks (one session per week). Group A Ss were given 54 signals in four matrices (2 by 2, 3 by 3,4 by 4, and 5 by 5). Four anchors within the range were also given and were additionally judged among the 54 signals. The size of the A group decreased weekly from 30 to 6 Ss. Delayed knowledge of results (KOR) was given at the end of each session and the same random order of transmitting signals was used in each session. Group B Ss completed an extra (6 by 6) matrix and had one additional anchor, but they received no KOR and the random order of signal transmission was always varied. There was no significant difference between subgroups. Channel capacity was not obtained but the maximum information transmission was 3.08 bits. Practice generally increased T_(X;y) at each session.     

Use of markov-encoded sequential information in numerical signal detection

Twelve Ss made binary decisions with feedback on numbers from one of two normal distributions with equal variances and unequal means. Sequences of distribution choices corresponded to first-order two-state Markov processes with probabilities of change of state of p₁ = p₂ = .50, p₁ = p₂ = .75, and p₁ = p₂ = .25. Performance was best (in d’ terms) when p₁ = p₂ ≠ .50. First-order sequential response dependencies tended to mirror the first-order stimulus dependencies. Violations of a fixed cutoff point decision rule were concentrated in the region of the average critical point, with a bandwidth of about 1/2σ, in which violations were strikingly more frequent than would be expected if they had occurred randomly. These results imply that in this task Ss are using a criterion-band decision rule instead of a fixed cutoff point rule, and that they are basing decisions in the region of the criterion band on information extracted from the sequence of decisions presented to them. The average bandwidth is generally different from the optimum bandwidth used by an ideal O in combining the two sources of information.     

CRT信号显示的刺激率和信号率对警觉作业的影响

本实验系统地考察了在不同刺激率、信号率条件下警觉水平的变化 ,并分析了以往警觉理论的适应条件。实验一采用 5次 /分、1 5次 /分和 30次 /分的刺激率条件 ,发现检测正确率在各条件下随时间的变化是由于 d′下降所致 ,而β值基本不变 ,可以认为警觉随时间下降是由于疲劳所致 ;中等刺激率条件下的 d′最高 ,低刺激率次之 ,高刺激率最差并且高刺激率导致被试唤醒水平降低。实验二在 30次 /分的高刺激率条件下变化信号率 (分别为 3次 /分、6次 /分和 1 2次 /分 ) ,发现信号率变化不会改变 d′,但导致β值的变化 ,可以认为高信噪比导致被试的唤醒水平升高     

Processing of tachistoscopic displays with controlled order of characters and spaces

The task used was designed to force Ss consistently to process the letters of a tachistoscopic display in the same spatial order, if Ss are able to process the letters in a brief display serially and if Ss have enough voluntary control over the selection of a processing order to use the order chosen by the E. In the main series of experiments the set of slides shown in each session included slides having a blank space in some position in the linear array of letters. For control, no-blank slides, a sharp, monotonic decrease in the percentage of correct detections of a signal letter with distance of the signal letter from the focusing dot was obtained. An unexpected result from the slides having a blank space was that detection of the signal letter was considerably more accurate on the slides having a blank space immediately following the signal letter than on the control slides having no blank space or the slides having a blank space immediately before the signal letter in the processing order. In one experiment blank spaces were replaced by black rectangles with no substantial change in the pattern of results. The results from the slides having a blank space or a black rectangle were interpreted as indicating that the onset of processing the image of a letter was determined by the distance in the display from the focusing dot to the letter and that the duration of processing an image of a letter was determined by the distance in the display from the letter to the next letter in the processing order.     

Ready-signal effects as a function of experimental design in simple reaction time

In the between-S design, 20 Ss had a visual ready signal presented on each trial; for another 20 Ss, the ready signal was always absent. The within-S design consisted of 40 Ss that experienced both ready-signal conditions in semirandom order. Two intensities of a 1,000-Hz tone were used as the response signals Ready-signal manipulation had pronounced effects under the within-S but not the between-S design irrespective of response-signal intensity     

Successive vs simultaneous processing of superimposed visual stimuli

A visual analogue of Savin’s (1967) auditory task was used to examine preferred order of recall and order of recall accuracy for two pairs of visually superimposed digits. Savin (1967) and Rollins, Everson, and Schurman (1972) found that Ss preferred to recall simultaneous auditory information in successive order, even though the information was presented over a single channel. In the present experiments, Ss were found to prefer strongly to recall visual information in simultaneous order. On the other hand, the results of Rollins et al (1972), that Ss are equally accurate when forced to recall simultaneous auditory information in either the preferred or nonpreferred mode, were replicated for this visual task. The results of these experiments, together with the experiment reported by Rollins et al (1972), indicate that verbal information is processed differently by these two sensory systems.     

Serial learning of nonsense shapes as a function of instructions controlling labeling

In the literature on visual contrast thresholds for sine wave gratings, little attention has been paid to the psychophysical methods used to obtain these spatial-frequency response curves. Here we report a comparison of such data obtained by two quite different psychophysical methods, but otherwise under identical conditions, using five Ss. Both experiments were run by computer: (1) In the method of adjustments, the computer program merely controls the order of the stimuli and records S’s contrast settings. (2) In the forced-choice staircase (FCS) technique, the program determines how often S can discriminate the sinusoidal grating from a uniform field, informs S of his accuracy, controls the stimulus contrast on the basis of S’s preceding responses, and brackets his threshold by a series of successive approximations. Method 2 eliminates criterion effects that occur in Method 1, and hence tends to minimize individual differences. However, the FCS technique requires an order of magnitude more observing time to obtain equally smooth contrast sensitivity curves. FCS also increases the/overall sensitivity of some Ss by as much as five times, but it does not significantly change theshape of the contrast sensitivity curve; both methods show strong effects of lateral inhibition at low spatial frequencies.     

The initial effect of noise on a simple vibrotactile learning task

In two experiments the effect of loud noise on a simple vibrotactile learning task was studied. After learning the task to criterion, 10 male and 10 female Ss received two pairs of test trials, one without noise, and one in continuous noise (a 1,000 cps pure tone at 90 dB SPL). An additional 10 male and 10 female Ss learned the same task and also received the same two pairs of test trials, but instead of receiving continuous noise for the second condition, they received an intermittent noise (random numbers presented at 2 sec intervals at 95 dB SPL). In the first experiment noise had a significant effect on the performance of the 20-subject group and also on the females in the group. Noise did not significantly affect the performance of males. In the second experiment noise had no significant effect on either males or females.     

Odor intensity and pleasantness for a diverse set of odorants

Data Analysis Office, U.S. Army Natick Laboratories, Natick, Massachusetts 01760 Observers compared the odor of butanol to the odors of various concentrations of 32 chemicals, and also rated the odor pleasantness and unpleasantness of these 32 odorants by a line matching procedure. All stimuli were presented to the observers by air dilution olfactometers. Odor intensity matches between each odorant and butanol were often describable by power functions. A derived magnitude estimate of odor intensity was obtained through a calibration of the butanol concentration scale. Most odorants grew less rapidly in intensity than butanol, and all odorants grew in intensity as decelerating functions of concentration. A more general function of the form P =: k₁ + k₂C^k3 was needed to account for the pleasantness-unpleasantness judgments. In this study, most odorants were rated either neutral or unpleasant. Observers showed far more variability in hedonic judgments than in intensity judgments.     

On the perception of a class of bilaterally symmetric forms

Two experiments were performed to determine the manner in which people perceive a class of bilaterally symmetric forms. In the first experiment, paired, comparison dissimilarity judgments and unidimensional single stimulus ratings were collected from the Ss. The second experiment involved the collecting of semantic differential and paired comparison dissimilarity judgments from two groups of Ss. The judgments and ratings from both experiments were compared to each other and to a set of objective measures of the forms by a series of multivariate statistical techniques. It was found that three primary attributes, orientation, convexity-concavity, and curvature, accounted for the perceptual reports, but the manner in which the attributes were used differed for different response procedures and for the same response on different occasions.     

Free sorting with stimuli clustered in a multidlmensional attribute space

An experiment was conducted to determine whether Ss leam, without knowledge of results or prior familiarization with the prototypes, to sort histoform stimuli generated by three probablistic rules into categories consistent with these mies. Seven Ss were asked to sort 30 stimuli (10 from each schema population) on each trial. No constraints were placed on the number of categories to be used. A statistic was developed to measure consistency between schema-defined categories and subjeet-defined categories. Four of the seven Ss met the leaming criterion, and demonstrated increasing consistency with the schema-defined categories across trials. In general, more categories than necessary were used to classify the stimuli correctly. The results raise several questions about classification strategies used by Ss in perceptual learning tasks with stimuli generated by probabilistic rules, and indicate the need for further research conceming the variables that influence perceptual category formation.     

Effects of temporal uncertainty on watchkeeping performance

Two experiments were conducted to assess the relative effects of signal density and regularity on watchkeeping performance. In Experiment I, three levels of density (6, 24, and 96 signals/hr.) were combined factorially with three levels of variability (coefficients of variation of 0.01, 0.10, and 1.00), and 10 Ss were assigned at random to each of the nine conditions. In Experiment II, five levels of density (6, 12, 24, 48, and 96 signals/hr.) were combined with the same three levels of variability, and 13 Ss were assigned to each condition. Each 5 monitored a visual “blinking-lights” display for an hour under instructions to detect and report the occurrence of certain “critical signals,” i.e., arrests of alternation of the lights. Response times (RT’s) to correctly detected signals in both experiments decreased as a linear function of logarithmic increases in signal density. An uncertainty metric, the signal surprisal due to density, was derived, and the watchkeeper’sRT was expressed as an increasing linear function of this measure of temporal uncertainty. Interpretation of these and other data support a functional, psychophysical approach to the study of watchkeeping behavior.     

Effects of eye movements on the rate of discovery and the vividness of visual images

Two studies investigated the effects of eye movements on the rate of discovery and the vividness of visual images. Eye movements were manipulated by having three conditions: (1) The Ss were instructed to make eye movements while generating images to noun pairs; (2) the Ss were instructed not to make eye movements, but to think about making eye movements while generating images to noun pairs; (3) the Ss were instructed not to make eye movements and not to think about making eye movements while generating images to noun pairs. In addition, the ease of generating images was manipulated by using noun pairs that differed in their image-evoking capacity; five of the noun pairs consisted of high imagery-evoking nouns and five consisted of low imagery-evoking nouns. The two experiments were similar, with the exception that a between-groups design was used in Experiment 1, whereas Experiment 2 employed a within-Ss design. The results of both experiments showed highly significant effects of noun-pair type on both the rate of discovery and the vividness of images, with the fastest and most vivid images occuring to the high-imagery noun pairs. The effects of the eye-movement conditions on the rate of discovery and the vividness of the images were not significant in either experiment, and these findings are discussed in terms of the relationship of ocular activity to imagery.     

The perception of clicks in linguistic and nonlinguistic messages

Three experiments were run analyzing Ss’ abilities to locate clicks in auditory messages. In Expenment 1 it was found that the intonation pattern of the linguistic message largely determined the types of errors Ss made in click placement; syntactic factors were only marginally effective and semantic factors were effectively irrelevant. In addition to these linguistic factors, there was evidence that such nonlinguistic factors as attention, memory, and response biases were contributing to the data. Experiment 2 supplied additional evidence favoring these nonlinguistic factors. Experiment 3 was a mock-up of Experiment 2 except that broad-band white noise was used as the primary message instead of English sentences. The patterns of placement errors Ss made in these several experiments (especially Experiments 2 and 3) were sufficiently similar to one another to force the conclusion that nonlinguistic factors are primarily responsible for the errors Ss make in trying to locate clicks in messages. A neo-Titchenerian attention hypothesis based upon the law of prior entry was proposed to account for the data.     

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.