Observer Judgments Research Articles

Brain activities immediately after finding rare targets

It is generally assumed that the prior knowledge about the frequency of the target occurrence would influence the identification of a stimulus. Nevertheless, whether this influence occurs immediately after finding a rare target is unknown as yet. To clarify this issue, Event-related brain potentials were recorded in the present study while subjects were presented with thousands of pictures and were required to indicate whether a categorical target such as a tool was in the display. The results showed that participants responded more quickly to the posttarget nontargets (PNTs, i.e. the nontargets that immediately followed the rare targets) than to the common nontargets (CNTs, i.e. the nontargets that did not immediately follow the rare targets). Compared with CNTs, PNTs elicited enhanced amplitudes at N1, N2, and parietal P2 components. Moreover, the N2 latency was longer overall for PNTs than for CNTs. These results suggested that the prior knowledge did not affect observer's judgment immediately; instead, the event of finding a rare target strengthened the processing of PNTs.

Fragments of the Roelofs effect: A bottom-up effect equal to the sum of its parts

The Roelofs effect is a distortion of perceived space that occurs when a large frame whose center is offset left or right from the objective midline is presented visually to an observer and causes a bias in the observer's subjective judgment of midline. Experiments were designed to test whether an isolated fragment (left or right end) of a Roelofs-inducing frame was capable of generating the Roelofs effect and to determine whether prior experience with intact frames would provide a top-down influence that would bias the Roelofs effect resulting from fragment presentation. Although the fragments did induce an effect, top-down information did not play a significant role even after a 5-day training paradigm. Instead, we found that the effect generated by an intact frame was equal in magnitude to the sum of the effects generated by the individual fragments. In addition, perception was found to be differentially affected by the two ends of the frame, with fragments falling in the right visual field causing a larger effect than those falling in the left.

The flash-lag effect as a spatiotemporal correlation structure.

The flash-lag effect refers to the phenomenon in which a flash adjacent to a continuously moving object is perceived to lag behind it. Phenomenally, the flash appears to be spatially shifted relative to the moving stimulus, and the amount of lag has often been quantified as the flash's nulling position, which is the physical spatial offset needed to establish perceptual alignment. The present study offers a better way to summarize flash-lag data. Instead of plotting data in terms of space, the psychometric function of the observer's relative-position judgment is drawn on spatiotemporal plot. The psychological process underlying illusory lag is formulated as spatiotemporal bias and uncertainty and their estimate as a spatiotemporal convolution kernel that best explains the spatiotemporal psychometric function. Two empirical procedures of kernel estimation are described. One procedure is to fit the free parameters of the kernel to experimental data for continuous motion trajectory. The second is to give an analytical solution to the kernel using experimental data for random motion trajectory. The two procedures yield similar kernels, with negligible spatial bias and uncertainty and substantial temporal bias and uncertainty. In addition, it is demonstrated that an experimental manipulation of temporal predictability of the flash can change the temporal bias in the estimated kernel. The results of this novel analysis reveal that the flash-lag effect is viewed as a spatiotemporal correlation structure, which is largely characterized by the tendency to compare the position of the flash in the past with the position of the moving item in the present.

Neurogenic stuttering versus developmental stuttering: An observer's judgement study

Neurogenic stuttering versus developmental stuttering: An observer's judgement study

INTER- AND INTRAOBSERVER RELIABILITY OF VENTILATORY THRESHOLD DETERMINATION IN CHILDREN

866 Ventilatory threshold (VT) is often used to assess aerobic fitness in children. However, the method has been questioned since the determination relies somewhat on the observer's judgement. The objective of this study was, therefore, to determine the inter- and intraobserver reliability of VT determination in children. Data were taken from a study on exercise capacity of children born prematurely (n=33) and controls born at term (n=21) tested at the age of 6-12 years for peak oxygen uptake (˙VO2peak). Subjects performed a cycling task starting at 0 Watt·kg-1 for 2 min. Workrate was then increased by 1 Watt·kg-1 every 2 min until volitional fatigue. Respiratory parameters were averaged every 15 s.˙VE/˙VO2, ˙VE/˙VCO2, and RER were plotted (1) over time (X-Time) and (2) over ˙VO2 (X-˙VO2).˙VCO2 was plotted over X-˙VO2 only. For each subject, the plots were copied 4 times and number-coded. Two experienced observers evaluated them independently for VT at 2 occasions, 4 weeks apart. Reliability was assessed by calculating the error E=√Σd2/2n expressed as percent of the measurements' mean (d-difference between related measurements). VT expressed as ˙VO2 in ml·min-1 could be determined in 40/54 children from X-Time and in 46/54 children from X-˙VO2. E between observers was 15.4% using X-Time and 7.2% using X-˙VO2. Intraobserver E employing X-Time was 12.5% (observer I) and 6.4% (observer II). The respective values for X-˙VO2 were 8.5% and 7.5%. In conclusion, inter- and intraobserver reliability of VT was high when X-˙VO2 was used but lower when time was plotted on the X-axis. This study does not support the notion that VT can not be determined reliably in a given data set.

Measuring performance efficiency and consistency in visual discriminations with noisy images.

These experiments measured the efficiency of disk discrimination performance, relative to an "ideal" observer, and compared 2 visually dissimilar tasks in which noisy image stimuli were identical for a physical calculation yielding optimum decisions. Performance consistency was measured by estimating the assumed underlying correlation in an observer's judgments about the same individual "frozen noise" images across independent replications of each condition. Larger disk sizes on the stimulus images considerably reduced observer performance efficiency (by a factor of 10) in both discrimination tasks, regardless of the image viewing distance. But even when efficiency was very low (5% or less), performance consistency still remained quite high (about 50%). About half of each observer's inefficiency appeared to reflect consistent (but suboptimal) perceptual "miscalculations" of the noisy stimulus information.

自動車用ヘッドアップディスプレイの明るさ感評価結果

Indoor evaluation experiments have been carried out on the perception of the brightness of car speed indications projected by an automobile head-up display (HUD).We did two types of experiment. One was to examine the influence of the observer's age on the evaluation data. The observers were to determine the appropriate brightness of the HUD as it changed from dark to bright (ascending order) and from bright to dark (descending order). The observers were categorized by age levels (in their 20s, 40s, or 60s).The other experiment had observers evaluate the brightness while we interfered with their observational concentration by having them do subsidiary tasks during the evaluation. As well as the subjective evaluation results, we also examined electrocardiograms from the subjects to calculate the RRV (R-R Variance), which expresses the extent of a mental load.The main results are:(1) The range of HUD brightness judged as appropriate is narrower for older people than for younger people.(2) Subjective judgments of HUD brightness perception changed when the observers also had to do a subsidiary task. In other words, evaluations range from too bright or too dark to neither too bright or too dark.(3) The RRV values revealed that the extent of the mental load differs according to the nature of the subsidiary task. When there was a heavy mental load, an observer's subjective judgments changed considerably.

2つの照明認識視空間の相互作用

One can immediately judge the state of illumination of a room by observing various objects in the room such as furniture and wall paper. The appearance of the objects, e.g., their color and brightness, constitutes the initial visual information about the room, and the recognized visual space of illumination, RVSI, of the room that the observer gains is based on that information. The observer's later judgment about the appearance of objects in the room is based on the RVSI. Here, we consider the interaction between RVSIs for two rooms connected by a window of variable size: one for an observer's room with Dlight type illumination and the other for a test room with Alight type illumination. The RVSI of the test room was evaluated by measuring the appearance of colors of nine test color charts placed in the test room as a function of the illuminance of the observer's room, which was varied between 0lx and 270lx, with the illuminance of the test room constant at 270lx; it was also measured as a function of the window size. The RVSI of the test room was not affected by the RVSI of the observer's room for the illuminance of 0lx through 1lx, but it was affected for illuminance above 1lx, and the effect increased for higher illuminance values. A greater effect was also found for smaller windows. The direction of color change of the color charts varied along the hue circle, depending on the hues. That phenomenon was explained using a chromaticity diagram.

Perceptional inequality and preferential judgements: An empirical examination of distributional axioms

There are two categories of income distribution evaluations: first, the more-or-less “value-free” perception of income inequality as a statistical dispersion; and second, the valuation of income distributions according to an explicit social welfare function which is meant to capture all of society's value judgements. These societal value judgements can be expressed in the form of preferences. Whereas the inequality perception of income distributions appeals to an observer's sober judgement, the revelation of preferences with respect to specific income distributions appeals to his or her sentiments. This paper is an empirical analysis which investigates the juxtaposition of preferences with respect to income distributions and corresponding perceptions of distributional inequality. We do this through a questionnaire in which attitudes towards various distributional axioms are tested. The source of our data is 1773 completed questionnaires collected from five German universities. Based on our data, we observe that individuals' preference orderings over the set of income distributionssubstantially deviate from their perceptions of distributional inequality. In fact, our test responses showed that even when some income distribution is judged to be more unequal than another, that distribution might be preferred, as it accords higher incomes to each individual. We hold that the preference for these greater incomes expresses a compensation for the increased degree of inequality. This explanation applies both to equiproportional and to equal fixed-sum increases in incomes, which implies a support of Paretian ethics.

Multiple classification and receiver operating characteristic (ROC) analysis.

The receiver operating characteristic (ROC) curve was applied to observer performances in a multiple-alternative decision task. It was shown that the probability of correct classification, a performance criterion often maximized in multiple-classification procedures, corresponds to the area under an appropriately constructed ROC curve. Degrees of confidence in the observer's judgment of 0, 1, ..., 10 were used for both classification and ROC rating. To demonstrate the validity of the method, 1,190 photofluorograms were examined by experienced staff radiologists to identify four cardiovascular conditions distinguishable on the basis of images of structural elements of the contours of the heart and great vessels. The classification matrices for three radiologists who achieved high, medium, and low performance ratings in this experiment are reported. The ROC curves are symmetric, with their points located around the off-diagonal. Differences between the overall probability of correct classification and the ROC curve index calculated from the same evaluator's data were very small, 0.004 to 0.011.

Participant and observer attribution of affect in interpersonal conflict: An examination of noncontent verbal behavior

This investigation explored the relationship between observer and participant attribution of affect intensity in interpersonal conflict interaction and the occurrance of verbal behavior. It was predicted that observer's judgments of affect intensity would account for more variation in verbal behavior that represents conflict than would participant's judgments of affect intensity. Videotapes of 37 dyadic conflict interactions were examined. The results indicate that one observer's judgment of affect intensity was a much better predictor of verbal behavior than were the other observer's judgment of affect intensity or either of the two participant's judgments of affect intensity. While some evidence was yielded to suggest that observers are more likely to be sensitive to behavior in their attribution of affect intensity than are participants, these results imply significant differences in the attribution of affect between some observers.

Visual Acuity of Infants and Young Children: Forced-Choice Preferential Looking Procedures

Traditional forced-choice preferential looking (FPL) procedures have been useful laboratory tools in the documentation of normal acuity development in infants and young children. FPL procedures have also been used in several clinical settings to assess acuity in infants and young children with a variety of visual disorders. Nevertheless, FPL procedures have limitations that may hinder clinical utility. The most serious problem is a statistical limitation that requires a large number of trials to produce a reasonably accurate estimate of acuity. Because of this limitation we developed the acuity card technique, a procedure that relies on an observer's subjective judgment of the highest spatial frequency grating an infant can detect during presentation of FPL-type stimuli. Results of initial studies indicate that the procedure is faster than and as accurate as FPL procedures in the laboratory setting. Tests of the clinical usefulness of the acuity card procedure are in progress.

The effects of sex and sex-role identity on the attribution of maladjustment

This study examined the effects of a stimulus person's gender and sex-role identity and an observer's gender and sex-role identity on the observer's judgments of the stimulus person's personality and level of adjustment. After having been classified as androgynous or nonandrogynous, 141 males and females viewed videotapes of a case conference on a bogus client. In the videotapes the client's gender and sex-role identity were factorially manipulated. As predicted, male clients and clients with a masculine sex-role identity were seen as possessing less favorable personality characteristics and as being less mentally healthy than were female clients and clients with a feminine history. Sex-role incongruence (e.g., a masculine female) influenced the subjects' judgments only of a female client. A sex-role congruent female was seen as more attractive and better adjusted than a sex-role incongruent female. The subjects' gender and sex-role identity did not influence their judgments of the clients in any consistent or interpretable fashion. Finally, it was found that the subjects were most influenced by sex-role congruence/incongruence of opposite sex stimulus persons. The discussion of these results centered on: (a) the relative influence of gender and sex-role identity on people's perceptions of a stimulus person and (b) the need for further exploration of how subject characteristics might influence these perceptions.

Human perception of visual air quality (uniform haze)

The National Park Service and the U.S. Environmental Protection Agency are cooperatively conducting ongoing studies of human perception of visual air quality. Major objectives of this program include: (1) determination of the relationship between judgments of visual air quality of actual three dimensional scenes and a surrogate slide representation of that scene, (2) examination of the effect of sun angle and meteorological conditions on perceived visual air quality, (3) examination of the effect of demographic background on observer's judgments of visual air quality, (4) establishment of a functional relationship between human perception of visual air quality and various electro-optical parameters for several different scenic vistas and (5) development of a model capable of predicting the sensitivity of a park to visual air pollution impact. Preliminary results of a previous study involving one vista revealed a linear relationship between human perception and apparent vista contrast for constant vista illumination and ground cover. A more general formalism for averaging vista color contrast appeared to account for effects that snow cover and varying illumination have on the sensitivity of perceived visual air quality to air pollution. These functional relationships are re-examined using a number of southwestern vistas. A first order model capable of predicting perceived visual air quality as a function of change in air pollution is developed. In addition, the relationship between perceived visual air quality of actual three dimensional scenes and pictoral surrogates is examined.

COMPARISON OF YES‐NO AND LATENCY MEASURES OF AUDITORY INTENSITY DISCRIMINATION

Rats discriminated auditory intensity differences of sinusoids at 3.0 kilohertz in a go/no-go signal detection procedure. Responses to the signal (hits) were reinforced with electrical brain stimulation, and misses produced a brief timeout. On intermixed noise trials, withholding of responses (correct rejections) was reinforced, and false alarms produced the time-out. In two test conditions, the signal was either the louder (100 decibels) or softer (90, 93, 96, or 99 decibels) of the pair of intensities presented within a set of trials. Each animal was first trained with signal value louder or softer, and reversed for the second condition so that the former noise value served as signal. Hits showed shorter latencies than false alarms, regardless of the relative intensity of signal and noise, and the magnitude of differentiation was proportional to signal-noise separation. Both hits and false alarms showed longer latencies as the discrimination became more difficult. Isosensitivity contours derived from the latencies showed close similarity across conditions; in comparison, the yes-no measure of detectability, d', showed greater variability. The similarity of latency differentiation across louder and softer signal conditions supports a detection model in which the observer's judgment is controlled by the distance of sensory effect from criterion on each trial, as opposed to the loudness of the tones per se.

The determination of optimal exposure to phobic stimuli in flooding therapy

The present study compared the value of various criteria for determining exposure duration to phobic stimuli in flooding therapy. Results indicated that basing exposure termination on a return to resting ranges of HR was not effective in increasing approach behavior, whereas basing termination on observer's judgements was quite effective. Employing self-reported anxiety reduction as the termination criterion was no more effective than using either the HR criterion or a procedure that combined all three criteria (HR, self-report, and observer's judgements). Self-reported fear data showed similar trends with the HR criterion again failing to produce any greater benefits than control procedures. Nine-weeks follow-up indicated a persistence of the behavioral changes with some loss of the gains in subjective anxiety, and a reduction in the differences between groups.

Concentric circular illusion and the "object" character

Two ways of theorizing may be distinguished in the explanation of the concentric circular illusion. The first tries to explain the illusion in terms of spatial interaction of the two contours forming the pattern, while the second in terms of the “figure-ground” relationship. The purpose of this article is to point out some faults of the first and to present some experimental evidence supporting the second point of view.In Experiment Ia, the distances from the observer of the three stimulus fields, i.e., the field outside the outer circle, that between the inner and the outer circles, and that inside the inner circle, were systematically varied, while the two circular contours were always presented on a plane at fixed distances from the observer (see Figs. 1 and 2). Thus, with the “figure-ground” or the “object” character of the whole pattern was modified, with the spatial relationship of the two contours being kept constant. The results showed that the amount of the illusion, measured with the usual method of limits, is not solely a function of the distance between the two contours (or the size ratio of the two circles) but depends on the so-called “object” character of the pattern. It was also shown that this was not due to the effect of accommodation or textural differences (Experiment Ib, c, d).In Experiment IIa, a modified method of magnitude estimation was introduced, and the “largeness” of the control circle was, estimated. The results suggested that the observer's judgement of “largeness” in many of the experiment of the concentric circular illusion must have been made in terms of “area” bounded by the contours, not in terms of the “distance between the two contours” or of “displacement of a contour”. The results of Experiment IIb, using the square comparison stimuli and the method of limits, supported this “area” concept again.

The effect of object familiarity on the perception of size and distance.

The perceived sizes and perceived distances of familiar objects were investigated in two experiments in which images of familiar objects were presented monocularly, one at a time, in an otherwise dark field of view. It was found that the angular size of the objects as well as their familiar size determined reported size. Reported distances were increasingly underestimated as a function of increasing simulated distances of the objects. The results are consistent with the conclusion that, as a function of the retinal size of the objects, the observer perceives the familiar objects as off-sized, and, that as a consequence of these off-sized perceptions, the observer's judgements of the object distances reflect inferential rather than perceptual processes.

Study of Per- and Poststimulatory Fatigue in Pitch Perception

While changes and recovery in loudness sensitivity have been studied over time by many investigators, changes in the perception of pitch have been observed only at discrete time intervals and changes during these intervals can only be attributed to normal variation or error. No graphic display of an observer's pitch judgments over time has been available for inspection under the usual psychophysical procedures. The method used in this study permitted the continuous recording of the subjects' perception of pitch over time under perstimulatory and poststimulatory conditions. In Expt. 1, pitch perception was studied under per- and poststimulatory fatigue with 60 and 90 dB sensation-level signals at 250, 500, 1500, 2500, and 4500 Hz. In Expt. 2, pitch perception was examined after stimulation of 100 dB SL for 10 min at the above frequencies. In Expt. 3, a fatiguing stimulus at 750 Hz was presented for two minutes at 120 dB SPL. Pitch perception was then studied at adjacent frequencies: 550, 650, 850, 950 Hz. No systematic change in pitch perception was observed under any of the experimental conditions. Since these findings conflict with similar studies, special attention was given to procedural and theoretical reasons for the discrepancies.

Study of per- and poststimulatory fatigue in pitch perception.

While changes and recovery in loudness sensitivity have been studied over time by many investigators, changes in the perception of pitch have been observed only at discrete time intervals; and changes during these measurement intervals can only be attributed to normal variation or error. No graphic display of an observer's pitch judgments over time has been available for inspection under the usual psychophysical procedures. The method used in this study permitted the continuous recording of the subject's perception of pitch over time under perstimulatory and poststimulatory conditions. In Expt. 1, pitch perception was studied under per and poststimulatory fatigue with 60- and 90-dB sensation-level signals at 250, 500, 1500, 2500, and 4500 Hz. In Expt. 2, pitch perception was examined after stimulation of 100 dB SL for 10 min at the above frequencies. In Expt. 3, a fatiguing stimulus at 750 Hz was presented for 2 min at 120 dB SPL. Pitch perception was then studied at adjacent frequencies: 550, 650, 850, 950 Hz. No systematic change in pitch perception was observed under any of the experimental conditions. Since these findings conflict with similar studies, special attention was given to procedural and theoretical reasons for the discrepancies.