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Using 40 Ss, an attempt was made to precondition a secondary reinforcer by pairing two lights during preconditioning, making the paired presentation of one of the lights and reinforcement contingent upon a button-pressing response during conditioning, and measuring the number of responses for presentation of the other light during extinction. Relative to controls, there was a preconditioning effect (p

Children, ranging in age from 31/2-41/2 years and 41/2-51/2 years were provided with successive discrimination training in which S+ was a white square on a black background and S- was a black background. Bidirectional size generalization testing with either a “booster” or “instructional” method indicated that (l)test method did not differentially affect generalization patterns; (2) younger children responded maximally to all test stimuli while spontaneously labeling the size stimuli “big” and “little”; (3) older children generated a group gradient composed of one subgroup who responded to all test stimuli and a second subgroup who responded to S+ only; (4) posttest verbal behavior suggested that the size cue controlled S+-only responding while controlling stimuli associated with flat patterns were color (“white”) and form (“window”). The results drew attention to stimulus selection processes in the stimulus generalization experiment.

To determine if S’s ability to perceive and to recognize a letter would increase with well spaced repetitions, even if the position and I or the typeface changed from flash to flash, four Ss were shown six flashes of single letters and were asked to guess the letter and to indicate whether or not they saw it clearly. Recognition (measured by both forced-choice guesses and by perceptual reports) increased at a constant rate whether an identical test letter was flashed on each trial or the form and/or position of the letter was varied (over four levels each) between flashes. The mean level of recognition was also unimpaired by variations in typeface and I or position, when measured by forced-choice guesses. With a perceptual report, recognition was lowered by variation of the test stimulus, apparently through a change in report criterion. These data suggest that the perceptual repetition effect must operate through arousal of the letter name or some other representation of the stimulus rather than by a simple sensory facilitation.

Visual generalization gradients to wavelength in the pigeon have been measured with stimuli differing in both wavelength and intensity. The gradient attributed to changes in wavelength may be due to differences in intensity. The original Guttman-Kalish experiment was duplicated essentially, but using test stimuli at two intensities at each wavelength. The gradients for the two intensities are nearly identical. Visual generalization gradients may be attributed safely to wavelength.

Evidence indicated that dilation can be produced, even in the presence of increased luminance, provided the stimulus is sufficiently arousing or novel. The results from a second study failed to support the hypothesis that pupil size is systematically related to rated affect of visually presented words. Possible artifacts of measurement are discussed.

Fourth-, fifth-, and sixth-grade children were trained and tested in a multiple-choice learning situation under both performance (guessing with knowledge of results) and observation (watching the performer) conditions. Although the observer superiority previously found for college students and grade-school children did not occur, there was a reliable trend in that direction from the fourth to the sixth grade.

Chromatic aftereffects to test gratings are affected significantly by differences in adaptation and test stimulus densities, i.e., number of edges per unit area. The strength of the aftereffect, as measured by the degree of angular disparity between adaptation and test grating orientation at which the aftereffect is lost, is a systematic function of adaptation and test density similarity.

The galvanic skin response (GSR) component of the orienting reflex was recorded for four groups of 12 Ss each. They were given 10 habituation trials to black on white numeric stimuli presented in seriatum. On Trial 11 an out-of-sequence test stimulus (TS) was delivered and was followed by one additional in-sequence number. The TS was either ±1 or ±11 places out of sequence. It was found that GSR magnitude to the TS was primarily a function of the amount of disparity provided by the TS, irrespective of the direction of that disparity. Dishabituation to the subsequent in-sequence stimulus was not, however, clearly present. The results were related to Sokolov’s neuronal model of habituation and to previous research.

Following 80 eyelid conditioning trials with a 400-, 600-, or 800-msec. ISI, Ss were given 20 extinction trials to a test stimulus, then shifted to the acquisition CS for 10 extinction trials. Generalized extinction was found negatively related to ISI with no systematic ISI trends observed for generalization of positive response tendencies.

An attribution-ofresponsibility (AR) questionnaire was administered to matched samples of Negro and white children representing four age levels. Ethnic differences were observed in the two youngest groups, whereas there were no ethnic differences among the older children. In the younger age groups, Negroes showed a generally less differentiated pattern of AR than the whites. The results were interpreted as supporting the hypothesis that a deprived cultural background retards the rate of learning norms concerning responsibility attribution.

As predicted, human Ss trained with three sizes of squares, intermediate size being “correct,” responded relationally to transposition tests regardless of similarity between training and test stimuli, providing sets (indexed by a task during training) were “relational”; but if sets were “absolute,” absolute responding was shown on similar tests, relational on dissimilar. Thus, had data from Ss with different sets been grouped, the resultant similarity function would represent no actual S. This new analysis appears fruitful in understanding findings not consistent with previous theoretical formulations.

The perimeter is designed for presenting test stimuli in any part of the field of view by remote control. It permits the examination of the potentials of the visual cortical area and their relation to the position of the stimulus in the field of view. If the subject perceives the test object, the α-rhythm is inhibited; if he does not, it remains unchanged. If subjective examination has revealed irregularities of the field, the method described allows it to be measured objectively. The instrument was tested on 48 persons, some healthy and some sick.

Vibrotactile thresholds were measured using a criterion‐free psychophysical method. 200‐Hz signals were presented unmasked and in the presence of three masker types: a 200‐Hz vibration in phase with the signal (experiment 1); a 200‐Hz vibration shifted in phase by 90° (experiment 2); a narrow‐band random noise centered at 200 Hz (experiment 3). The threshold shift was measured as a function of masker SL. The form and position of the masking curves resulting from experiment 1 could be accounted for by an energy‐detection model when a peripheral threshold was assumed. The threshold model described the masking curve over its entire length. Without changing subject‐dependent parameters, the same equation, adjusted only to account for quadrature summation of signal and masker in the stimulus domain, accurately predicted the effects of the sinusoidal masker in quadrature with the test stimulus (experiment 2) as well as the effects of random noise (experiment 3). Although an energy‐detection model without a thre...

Two experiments using rats as subjects examined the relative degree of interference (helplessness) occasioned by pretreatment experiences with either passive-escape training or noncontingent, inescapable shock. In Experiment 1, passive-escape subjects initially learned to terminate shock by not running (forward or backward) and subsequently were tested in a shuttle box appartus that required an instrumental running response for termination of a moderate level (.5 mA) shock. A group of subjects yoked to passive escape subjects during the initial training stage experienced inescapable shock prior to shuttle-box testing. An additional group of subjects experienced no pretreatment but was required to learn that shuttling (running) terminated shock during the test phase. Experiment 2 included the same three experimental conditions except that a more intense shock (.8 mA) was used during shuttle-box testing. The results indicated that interference (helplessness) effects occurred uniformly for passive-escape and yoked subjects with a moderately aversive test stimulus (Experiment 1). With a highly aversive test stimulus, interference effects were observed following passive escape training, but were absent following pretreatment exposure to inescapable shock (Experiment 2). The theoretical implications of these data for interference theories (viz., the learned helplessness hypothesis and the incompatible motor response hypotheses) were discussed.

An experimental method for the investigation of direction‐specific characteristics of the auditory system is presented. The subjects were exposed to narrowband signals of 100 Hz, 1 kHz, and 6 kHz mean frequency. Directed acoustic motion (adapting stimulus) was presented clockwise/counterclockwise) in three ways: (1) actual sound source motion (loudspeaker rotating around the subject), (2) simulated motion via earphones, varying interaural intensity (ΔI), and (3) simulated motion via earphones, varying interaural‐time delay (Δt). Aftereffects in the opposite direction were observed in all three cases, but in case 3 (Δt) for 6‐kHz signals only. Unlike the visual analogue (waterfall effect) no apparent countermovement occurred, but rather a shift in the localization of the stationary test stimulus (approximately 2°, 1.2 dB, 30 μs, respectively). The results provide evidence for direction specific auditory subsystems in humans, i.e., for null‐point displacements caused by the adaptation of direction‐sensitive movement detectors [cf. J. A. Altman, Exp. Neurol. 22, 13–25 (1968)]. In support of physiological and anatomical findings (cf. Keidel, Neff, and Whitfield), the frequency dependence in case 3 (Δt) may indicate that the observed phenomenon is of cortical origin. [Based on the author's doctoral thesis, University of Gottingen (1977).]

In previous studies we have reported long‐lasting changes in the pitch of a complex sound following its association with a sound of a different pitch. The present study concerned whether a sound altered in pitch would show pitch adaptation effects commensurate with its pitch or frequency status. The test stimulus was the sixth, seventh, eighth, and ninth harmonics of F0 196 Hz. The conditioning tone was the first five harmonics of F0 204 Hz and the adapting stimulus was the first five harmonics of F0 200 Hz. Stimuli F0 196 and 204 Hz were heard in association for 30 min each day for 6 days. This resulted in a shift of F0 196 Hz to a pitch near 204 Hz. The results indicated a pre‐conditioning adaptation of the pitch of F0 196 Hz downward and a post‐conditioning upward shift. While the pitch change was in process and near 200 Hz, no adaptation occurred. The results will be discussed with reference to plasticity of the auditory system.

In Reply. —While significant clinical problems were present among the patients included in the report by Avilla and von Noorden, 1 it is difficult to compare their results in five clinical patients with our study 2 of 483 elementary schoolchildren for the following reasons. Results of stereoacuity were obtained from a single presentation of the TNO test stimulus; there was no effort to have the child show repeatability of that performance. Other stereoacuity test conditions (eg, distance at which the test was conducted and the lighting used) were not enumerated. The sample size was limited. Testing was not done under masked conditions. Specifically, our RDE test distance was 2 m. By moving the test farther away, the test figure became more difficult to see for nonstereoscopic reasons. However, we indicated in our article that the favorable results we obtained with the RDE test do warrant further investigation of the procedure

It has been demonstrated that listeners can identify the intended vowel in n CVC syllable even when the vowel nucleus has been attenuated to silence, leaving only onglides and offglides (Silent‐Center syllables). Verbrugge and Rakerd [Lang. Speech 29, 39–57 (1986)] constructed “hybrid” Silent‐Center syllables by cross‐splicing onglides and offglides of citation‐form CVC syllables spoken by a male and a female talker such that the formant trajectories were discontinuous. Identification of the intended vowel in hybrid syllables was no less accurate than vowel identification of the single‐talker Silent‐Center syllables. The present study replicates this research with syllables spoken in a earlier sentence “I say the word /dVd/ somemore,” using ten American‐English vowels. Hybrid Silent‐Center stimuli were prepared by crossing the stimulus sentences so that the sentence started with one talker and switched to the other talker after the silent portion of the test stimulus. Silent‐Center Control stimuli were al...

Levitt constructed a new projective test, primarily for use in forensic evaluations, the Personal Orientation Device (Levitt & Lester, in press). In this test, the subject is presented three sheets of papcr (one at a time), each with a circle drawn on it, and asked to draw three lines on each test stimulus. Incidental to the major purpose of the test, Levitt wrore a manual for scoring the protocols so as to predict Guilford-Zimmerman Temperament Survey scores2 The present study was devised to test whether Levitt's suggested method for scoring and interpreting the device does predict Guilford-Zirnmerman scores. The Guilford-Zimmerman Temperament Survey ( 1949) was administered to 21 females and 7 male students in a psychology course. Their mean age was 23.5 yr. (SD = 8.8 yr.). Subjects were also administered the Personal Orientation Device individually by one investigator. The latter protocols were then scored by the other investigator who had no knowledge of the Guilford-Zimmerman scores of the subjects, but was told the sex, age, and handedness of each subject. The predicted Guilford-Zirnmerman scores of each subject were made on 6-in. graphic rating scales. The prediction from the Personal Orientation Device of the subjects' scores on the Guilford-Zimmerrnan were correlated by the product-moment method with raw scores obtained on the Guilford-Zimmerman Survey. The personal-orientation predictions were associated with only one actual GuilfordZimmerman score of 10 (Scale A, r = 0.34, one-tailed p < 0.05). It must be concluded that the Personal Orientation Device did not predict GuilfordZimmerman Survey scores accurately.

A first estimate of the optimum frequency‐gain characteristic for each ear was obtained using psychoacoustic data. The frequency‐gain characteristic was then adjusted systematically so as to obtain an improved estimate of the optimum frequency‐gain characteristic. A paired‐comparison procedure was used with running speech against a noise background as the test stimulus. An estimate of the optimum binaural condition was then obtained by using the estimated optimum monaural condition in each ear. The frequency‐gain characteristics in the two ears were then adjusted systematically and the paired‐comparison procedure was used to compare conditions. For six of the eight hearing‐impaired subjects tested, the best binaural condition was the combination of the two best monaural conditions. This result was found for both the SoNo and SoNπ‐conditions. The two subjects who did not fit this pattern also showed high test‐retest variability in their paired‐comparison judgements. [Research supported by PHS Grant No. P01‐NS 17764.]

This exploratory study was an investigation of the use of film as a test stimulus for the measurement of learning in family life classes. A teaching-testing procedure which utilizes film in both the instruction and evaluation of students is described. The use of films for simulation in family life education has implications for increased instructional effectiveness and the potential transfer of concepts to life situations.

Dynamic variations in the strength of echo suppression were investigated through earphone simulation of the free‐field precedence effect. Each test stimulus consisted of two click pairs, with the interaural time parameters of the leading and lagging pairs reflecting stimuli originating from opposite sides of the head. Echo thresholds, the minimum lagging click delay required for subjects to report hearing an echo click, were obtained in two basic conditions: (a) test click presented in isolation, and (b) test click preceded by a train of clicks identical to the test click. The most striking finding was that the presence of the preceding click train usually elevated the echo threshold of the test stimulus relative to its threshold when presented in isolation, suggesting that echo suppression builds up during the click train. The magnitude of the effect was influenced by the number of clicks in the train and the period of silence between the end of the train and the test click. The effect is surprisingly pe...

The impact of different stimulus parameters on judgments has been doggedly investigated in numerous settings with multiple and varied experimental designs. It seems possible now to suggest a theoretical scheme for predicting the constellation of variables necessary and sufficient to produce contrast and proactive summation effects. By judgmental contrast we intend those cognitive and affective processes determined by the stimulus simarion which cause judgments of a given stimulus to be displaced away from the subject's "anchor," i.e., the attitude positions, past experiences, previous commitments, etc., with which the subject enters the critical judgment situation. Proactive summation denotes those processes in a stimulus situation whereby the effects of earlier stimuli "spill over" or add to the effects of the test stimulus thereby increasing or intensifying the critical judgments. In sequential judgments contrast effects can be expected to occur only when prior judgments are anchored, as by overt expression or public recording of one's opinions, and the sequence involves a sharp disjunction, that is, there is a marked difference in a crucial parameter between the test stimulus and the preceding stimuli. With minimal discrepancy assimilation may result. Proactive summation occurs when prior judgments are unanchored and the sequence is unchanging (the test stimulus does not differ significantly from the preceding stimuli with regard to critical variables). Also, the initial stimuli must be of a high intensity in order to manifest its spill-over effect onto the test judgment; otherwise, the proactive summation will remain undetected.

A series of experiments were conducted in which variations of the selective adaptation procedure were employed with a synthetic /bi/‐/di/ continuum for three female observers in an effort to obtain a systematic mapping of the selective adaptation phenomenon. The first experiment consisted of a series of adaptation sequences each followed by a labeling task in which members of the continuum were randomly presented for identification. Trials were either massed (two minutes between trials) or distributed (20 minutes between trials) in presentation. The degree of adaptation in the two conditions was not significantly different. The second experiment examined adaptation onset and involved varying the number of adaptors presented prior to either a labeling or a random ABX discrimination procedure. Results indicate that labeling and discrimination do not exhibit the same course of adaptation. In the third study, the interval between the last adaptor and the first test stimulus was manipulated to observe the adaptation decay functions for both labeling and discrimination. The results again point to a dissociation between labeling and discrimination with a differential rate of decay for each measure. Findings are discussed in terms of the current hypotheses proposed to account for selective adaptation. [Supported by a grant from NSF.]

A computer was used to generate three different waveforms from the same component frequencies by setting the phases of the components so they were either homophasic (all component sinusoids start at 0°), diphasic (sinusoids alternate between − and +45°), or heterophasic (starting phase randomly selected). The pitches evoked by these waveforms were investigated by asking listeners to match a pure tone to all the pitches they could distinguish in a test stimulus, and to rate the saliency of each pitch. Data from three listeners indicated that the pitch of the test stimuli could generally be matched by pure tones whose frequencies are around the fundamental (f1) or the octaves 2f1 and 4f1. Waveform patterning had no significant effect on the overall distributions of periodicity pitch matching responses. However, clear trends could be discerned from the ratings listeners assigned to the saliency of the pitches. A major finding was that the highest ratings of f1 pitch “strength” were always obtained for homoph...

Vibrotactile thresholds were measured at a single site on the thenar eminence in the presence of maskers set at different sensation levels. Measurements were made using a two‐interval, forced‐choice tracking paradigm. Maskers, either narrow‐band random noise or sinusoids, were presented simultaneously with test stimuli of different frequencies. Predictions of threshold shifts as a function of masker intensity were made for individual subjects based on their absolute vibrotactile thresholds and a duplex model of mechanoreception. The results showed that masking occurred within either the Pacinian or non‐Pacinian receptor system, but masking virtually disappeared when masker and test stimulus occurred in different channels. [Work supported by NIH.]

Eighty male and 80 female college students were shown a stimulus light of 525 nm, following instructions to remember it, and then were immediately tested for generalization (recognition) with a successively presented set of stimuli including 525 nm and six longer wavelength values. Subjects rated each test stimulus on a 6-point scale ranging from "surely same" as the original stimulus to "surely different." Both men and women showed a central tendency shift. Although the stimulus perceived as most likely to be the original (the mode) shifted to 545 nm in both groups, the men showed a greater mean shift than the women. Shifting was nearly complete in both groups within the first series of test stimuli with the men shifting faster. These findings replicate a 1972 report by Giurintano of greater central tendency shift in men than in women in a line angle generalization task, challenging an assumed analogy between our generalization task and the rod-and-frame test, in which women typically show the greater distortion. The analysis of central tendency shift within the first test series reveals that it occurs much earlier than previously believed.

This book is primarily the photographic presentation of a series of normal and abnormal reflexes. The pictures are accompanied by legends in telegraphic style that describe test positions, test stimulus, and "positive" and "negative" reaction. The philosophy of the presentation is based on classic segmental reflex concepts of Magnus and Sherrington. The very brief text gives the developmental age range in which most of these complex reflex motor patterns are normally elicited. As it stands, the book is a useful description of a pragmatic methodology with a clinical developmental correlation. It also has the advantage of pointing to the neurophysiologic basis of the abnormalities of the motor system in the handicapped child. However, the implied correlation of reflex pattern with anatomical level of involvement is primarily based on studies in lower animals. Application of the anatomical implications in the human may, therefore, be inappropriate. Only limited clinical-pathologic correlation has been

Vibrotactile thresholds for the detection of a 50‐ms vibratory stimulus on the thenar eminence of the hand were measured in the presence of and in the absence of a 700‐ms suprathreshold vibratory masking stimulus. When thresholds were measured in the presence of the masking stimulus, stimulus‐onset‐asynchrony was varied so that backward, simultaneous, and forward masking could be measured. The amount of masking, expressed as the difference between thresholds for detecting the test stimulus in the presence of and in the absence of the masking stimulus, was greatest when the test stimulus was presented near the onset or offset of the masking stimulus. For both backward and forward masking, the amount of masking decreased as a function of increasing stimulus‐onset‐asynchrony with the decay rate being greater for backward than for forward masking. Comparisons were made of the amounts of masking measured when the test and masking stimuli were both sinusoids, when the test and masking stimuli were both noise, a...

Spectral sensitivities measured by a constant CFF criterion are much narrower at high frequencies than at low frequencies. Neutralizing the chromatic adaptation produced by the test stimulus eliminates this effect. The proposed explanation of spectral narrowing is that R and G cone responses cancel each other at certain frequencies because of wavelength-dependent latency differences.

A psychological experiment was executed binocularly for a bipartite or a separated field. The viewing subtence was 2° in both fields and the spatial separation in a separated field was 1°. Seven observers adjusted the luminance of a white comparison stimulus to appear equally as bright as a test stimulus of a liquid crystal cell. Red-, green-, blue-color under the tunable birefringence mode were shown as a test stimulus. The ratios of the mean observer in a bipartite field were 1.35±0.23 for red, 1.20±0.13 for green, 1.06±0.13 for blue, and lower than those in a separated field.

Rod system increment threshold functions (ITFs) were studied in patients with cone-rod dystrophy (CRD). Rod thresholds (I(t)) for a 104-min, 500-nm test stimulus (TS), superimposed on an 11 degrees long wavelength background (luminance I(b)), were measured in eleven CRD patients and fourteen normal subjects. Thresholds in normals were also measured using a 7-min TS. A modified version of Weber's law [logI(t) = logK + log(I(n)(b) + c)] was fitted to the data from each subject and test condition to yield a description of the ITF in terms of the free parameters K, c, and n. Four of the CRD patients exhibited an abnormally high absolute threshold; of these, two showed abnormalities in K and c consistent with a reduced efficiency of quantum capture by the rods. Abnormalities in the ITFs of CRD patients did not resemble the effect of reducing the diameter of the TS from 104 to 7 min in normals. This suggests that threshold abnormalities in the CRD patients did not result from altered spatial summation. The results illustrate use of a parametric representation of the ITF to evaluate the loss of sensitivity in visual disorders.

The common measures used in evaluating the magnitude of a noise (Lx, Leq, and etc.) correspond to first‐ and second‐order statistics of the distribution of sound levels. There are, however, perceived differences between sounds that have the same values of these statistics. It is therefore necessary to consider the spectral properties of the waveform envelope which correspond to higher‐order statistics. In the present experiments the subject compares a test stimulus and a reference stimulus and selects the one which appears to be fluctuating more rapidly. The reference stimulus is a noise whose waveform envelope is a noise with a low‐pass cutoff which varies from 0.125 to 8 Hz. The point of subjective equality is determined by adjusting the modulation frequency of the test stimulus, a sinusoidally modulated noise, in an adaptive procedure. The results indicate that when the median frequency of the spectrum of the envelope is above 1 Hz, it is a reasonably good predictor of the subjective rate, when the med...

The results of this study indicated that the interval between the standard and the test stimulus has little, if any, effect on the listener's ability to perceive an intensity‐produced lateral shift in a binaurally fused auditory image at frequencies of 1 and 4 kHz.

The effect of surround luminance on relative latency of response to a test stimulus was measured with the perceived-order method in which asynchrony between two lights is varied to make the lights appear subjectively simultaneous. Increasing surround luminance from zero to levels high enough to impair test-stimulus detectability resulted in reduction of test-stimulus latency (facilitation of response speed) by 100 ms both in the rod-free area of the fovea and in the periphery. Since appreciable facilitation of response speed was obtained in the rod-free area of the fovea, suppression of visual noise would seem to be a more plausible explanation of the facilitation effect than inhibition of rod activity. Variation of surround luminance was also found to have a much greater effect than variation of test-stimulus luminance.

The long (binocular) inducing period required by Bergman and Gibson to generate a measurable slant aftereffect was not necessary for a highcontrast surface. The aftereffect for the black-on-white lattice pattern dissipated exponentially. The complex surface, however, produced concomitant interfering effects, possibly decreasing the precision of aftereffect measures. A simpler surface, of vertical contours, sufficed for relatively accurate binocular (but not monocular) adjustments to the vertical. This pattern also produced interfering effects, possibly accounting for the correlation of aftereffect variance with inducing-figure slant. The five studies suggest using a single vertical contour as both inducing and test figures to study a hypothesized relationship between tilt aftereffect and slant aftereffect. A sensory spatial aftereffect occurs when the judgment of some spatial property of a test stimulus is modified as a result of prolonged stimulation by an inducing stimulus. The aftereffect is assumed to be a simple additive component and is defined as the algebraic difference between a prestimulation judgment (pretest) and a poststimulation judgment of the test stimulus (posttest).' Spatial aftereffects in the third dimension of visual space were first demonstrated by KShler and Emery.2 They reported, for example, that a frontal-parallel cardboard strip was judged to be slanted in one direction following fixation of a similar strip slanted in the opposite direction. Later, Bergman and Gibson reported the occurrence of a slant aftereffect induced by an irregularly textured burlap surface with its edges obscured from view.3 The mean afterReceived for publication by Professor E. B. Newman, August, 1967. The research was part of a thesis awarded the M.A. at the University of Sydney, 1968. The author wishes to thank Professor R. H. Day for his assistance throughout the project. 1 J. J. Gibson, Adaptation after-effect and contrast in the perception of curved lines, J. exp. Psychol., 16, 1933, 1-31; W. Kbhler and H. Wallach, Figural aftereffects: An investigation of visual processes, Proc. Amer. phil. Soc., 96, 1944, 269-357. Later investigations have usually not departed from this convention. 2 W. Kdhler and D. A. Emery, Figural after-effects in the third dimension of visual space, this JOURNAL, 60, 1947, 159-201. 3 R. Bergman and J. J. Gibson, The negative after-effect of a surface slanted in the third dimension, this JOURNAL, 72, 1959, 364-374.

The concept of stimulus-generalization depends upon the demonstration that the various stimuli can be discriminated in a situation other than the test of generalization. It has been tacitly assumed that the auditory stimllli, such as those used by Hovland in studies of generalization, although unquestionably discriminable in terms of differential judgments, would also be discriminable if tested by other psychophysical techniques.1 Investigations of Pollack and Garner, in which absolute judgments were utilized, resulted in a surprisingly small number of discriminable stimuluscategories over the auditory dimensions of pitch and loudness.2 Both studies agreed in the finding that on the average only 4-6 discriminable categories were possible over ranges of 100>8000 at intensities of 5-lOo db. Inasmuch as the test of generalization does not incorporate differential discrimination, estimates of stimulus-discriminability based on absolute judgments would appear to offer the more appropriate technique for determining the signiScance to be attached to the test of generalization. When the small ranges of values used in the studies by Hovland (1502000 at 40-86 db.) are contrasted to the larger ranges that Pollack and Garner found necessary for reliable absolute judgments, Hovland's choice of stimuli seems too narrow. The present study was designed to investigate the discriminability of those stimuli utilized in Hovland's study of generalization, employing (a) the method of absolute judgments, and (b) a modified method designed to approximate the conditions of generalized tests. The results of the two

The apparent brightness of a test field can be substantially reduced by an extended-duration surround. In experiment I, test-field luminance was adjusted to match the brightness of a reference stimulus. Over a wide range of surround luminance, latency was measured by comparing test-stimulus and surround-field onsets, using the perceived-order method, in which the temporal interval between the two stimuli is varied to obtain subjective simultaneity. A series of control observations was made using test stimuli covering the same range of test-stimulus luminance that was used in the main series of observations, but with no surround field. Latencies of test stimuli were found to be considerably shorter with high-luminance surround fields than with no surround. Apparently, high-luminance surrounds resulted in reduction of latency of response to the test stimulus (facilitation of response to the test stimulus). In experiment II, a constant test-stimulus luminance was used. Reduction of latency of response to the test stimulus was found to increase with increasing surround luminance when surround luminance exceeded test-stimulus luminance. Supplementary observations indicated that the reduction of test-stimulus latency was not an artifact of dark adaptation.

Significant masking effects were found for a 40-g tactile stimulus applied either ipsilaterally or contralaterally to a threshold-value test stimulus. Consistent with the known contributions of lateral inhibition and central summation to ipsilateral masking, the ipsilateral effect was significantly greater than the contralateral (which did not vary with the arm receiving the test stimulus), the two effects showing nonoverlapping distributions in the same observers.

The ability to identify the longer of two straightedges placed along the volar surface of the forearm depended on the difference in length between the two lines and the absolute length of one of them (the standard). The difference limen increased slowly with the standard's length but was generally quite small, about 5/16 in., considerably smaller than the two-point limen for the same subjects and area of stimulation. With the straightedges placed across the arm, the difference limens were smaller yet. Ratio estimations (halving and doubling) suggest that subjective length depends on areal as well as circumferential (linear) aspects of the stimulus. The psychophysical literature on tactile perception concerns two-point thresholds, almost exclusively.' Some studies involve the perception of size or length by active manipulation with the fingers (Kelvin, 1954; Kelvin and Mulik, 1958). Others use lines or discs to contrast perception in different modalities, including skin senses (Jastrow, 1889; Lobb, 1965; Davidon and Mather, 1966). The discrimination of lines or discs passively impressed on the skin has only recently been made a subject of investigation. The first fact to be reported was that size discrimination on the skin has far more acuity than would be supposed from the previous literature on two-point thresholds (Vierck and Jones, 1969). Vierck and Jones used plastic cylinders impressed on a subject's skin as discs. In any one determination, two discs differing in diameter were presented to the subject, who was asked to say whether the first or the second was larger. The two investigators obtained difference limens ranging from 2 to 6 mm in diameter. For example, when the standard stimulus measured 25 mm in diameter, a test stimulus with a diameter less than 4 mm longer could be successfully discriminated 75% of the time. Since the two-point thresholds reported in the literature generally range upward of 40 mm, these difference limens were on the order of one-tenth as large. The purpose of the present study was to extend the earlier observations on size discrimination to lengths of lines. Several questions suggested themselves immediately. Are lines easier or more difficult to discriminate than discs? Does it matter whether the line's orientation on

This research represented an attempt to clarify the relations between loudness changes and threshold shifts following the cessation of an auditory stimulus. A 400‐msec, 1000‐Hz sinusoid served as the “fatiguer” and, following a specified recovery time, a 50‐msec, 1000‐Hz test stimulus was presented. The test stimulus was always delivered to the ear stimulated by the 400‐msec signal, but in the case of loudness judgments, simultaneous with the test stimulus, a comparison stimulus was presented to the opposite ear. The entire stimulus sequence was recycled every 4 sec. Thresholds were obtained by varying the level of the test stimulus while loudness was determined by adjusting the level of the comparison stimulus so that loudness in the two ears was equal. In general, threshold shifts were much greater than loudness shifts when both were measured in decibels. Loudness recovery proceeded more slowly than did the recovery of threshold. The sound pressure of the 400‐msec stimulus produced marked changes in the...

Temporal summation characteristics of the human eye have been studied by various authors by measuring the increment threshold when two test stimuli are presented successively. Among other things, some have observed an inhibition between the effects of two flashes for a certain inter-flash interval and others have not. Here a similar experiment is carried out with a red test stimulus superposed upon a red adapting field. Inhibition is observed at an interval of 52 or 70 msec, depending on the adapting level. Such an inhibition is also found when two stimuli are both negative. The introduction of a negative test stimulus into the double-flash, increment-threshold technique is a new aspect of the present work. Some new phenomena are observed, particularly, that a positive and a negative flash summate with each other at the interval where double positive or double negative flashes yield inhibition. The luminance ratio of the two stimuli (positive or negative) was freely adjusted and new information concerning the linearity of the summation was obtained. Based on these findings, hypothetical response-potential functions have been derived, which are assumed to be responses in the visual system at some peripheral level.

When an increment threshold is measured as a function of the radiance of an adapting field, the so-called threshold-versus-radiance curve is obtained. Stiles has shown by the two-color threshold technique that this curve is not necessarily smooth but can have inflections whose nature depends upon the conditions. From this he reasoned that the mechanism responsible for the threshold changes from one to another with a change of adapting level, all conditions otherwise being kept constant. In the present paper it is shown that an analogous situation can occur with the threshold-versus-duration curve, which is sometime called a temporal summation curve. Instead of a change of adapting level, a change in the duration of the test stimulus is considered. An assumption is made that each mechanism has its own threshold-versus-duration curve, and that the over-all threshold-versus-duration curve is determined by their relative positions. As an example of the utility of this analysis, two sensitivity curves of the eye were obtained with test stimuli of two different durations, 100 and 12.5 msec. It is argued that they are different in shape because of a change in the contribution of the responsible mechanisms which can be interpreted in terms of the relative positioning of threshold-versus-duration curves.

A test stimulus consisting of square waves repeated 200 times/sec and filtered so as to bandpass 1000–1250 Hz, was presented once each 5 sec. Other stimuli—a 200‐Hz tone, a 1000‐Hz tone, or a train of filtered signals identical to the test stimulus—intervened once per second between successive test stimuli. The question asked was, “What is the influence of each intervening stimulus condition on the responsiveness to the test stimulus?” The results showed that the 1000‐Hz tone and the filtered square waves suppressed greatly the evoked response (N1P2 component) to the test stimulus. The 200‐Hz tone did not. These data suggest that the N1P2 component of the evoked response reflected the acoustic spectrum of the filtered signal, not its modulation rate. If N1P2 can be taken validly as an index of auditory cortex activity, one can infer from these results that periodicity differences in stimulation at the periphery are not converted into place differences at the level of the auditory cortex.

The temporal course of reduction of test-stimulus effectiveness under conditions of metacontrast was studied with two different suprathreshold brightness-matching procedures. (1) Test-stimulus luminance was varied to make apparent brightness of the test stimulus equal to the brightness of a constant-luminance reference stimulus. (2) Reference-stimulus luminance was varied to match the apparent brightness of a test stimulus maintained at constant luminance. Functions obtained from two observers when the test-stimulus luminance was varied were typical metacontrast functions with maximum reduction of test-stimulus effectiveness when the test stimulus preceded the background by 50 ms, and the shape of the functions was highly similar to functions obtained previously with a disk–ring stimulus configuration. Functions obtained by varying reference-stimulus luminance were highly variable both between observers and within observers. The difficulties encountered with this second method probably resulted from glare from high-luminance test and surround fields.

This paper presents the results of subjective tests related to hearing in concert halls. The influence of nonexponential decay on the subjectively felt reverberation was investigated by comparing non‐exponentially reverberated sound signals with exponentially reverberated ones with different reverberation times. Two types of nonexponential reverberation were investigated: (1) reveration with different initial and final decay rates and (2) reverberation with increased or decreased energies in the direct sound and early reflections. Subjects were asked, in paired‐comparison tests, which stimulus in each pair sounded more reverberant. In another experiment, low frequencies (below 300 cps) were eliminated from the direct component in the test stimulus and added, with a delay, to the reverberation. The test stimuli were compared with reference stimuli whose low‐frequency components were attenuated by specified amounts. The subjects were asked which of the two stimuli had more low frequencies. Speech and music were used as test signals. The different reverberators and filters used were simulated on a digital computer.

Previous studies have demonstrated that central masking depends on the time pattern of stimulus presentation. When both the masking and masked stimuli are pulsed simultaneously, the masking effect amounts to about 10 dB, when the masker is continuous and the test stimulus pulsed the effect decreases to a few decibels. In order to study the temporal course of central masking more analytically, the contralateral threshold shift was investigated by means of 10‐msec tone bursts. The masker consisted of 250‐msec bursts of tone or random noise, repeated at a rate of one per second, and the test bursts were presented at various time intervals from the onset of masking bursts. The results show that the contralateral threshold shift may exceed 10 dB at the onset of masking bursts. It decreases rapidly within about 15 msec and more slowly thereafter. In a matter of 200 msec, it is reduced to a few decibels. When the intermittent masking and test stimuli are turned on simultaneously, the threshold shift gradually de...

Introduction Immediate responses towards emotional utterances in humans are determined by the acoustic structure and perceived relevance, i.e. salience, of the stimuli, and are controlled via a central feedback taking into account acoustic pre-experience. The present study explores whether the evaluation of stimulus salience in the acoustic communication of emotions is specifically human or has precursors in mammals. We created different pre-experiences by habituating bats (Megaderma lyra) to stimuli based on aggression, and response, calls from high or low intensity level agonistic interactions, respectively. Then we presented a test stimulus of opposite affect intensity of the same call type. We compared the modulation of response behaviour by affect intensity between the reciprocal experiments. Results For aggression call stimuli, the bats responded to the dishabituation stimuli independent of affect intensity, emphasising the attention-grabbing function of this call type. For response call stimuli, the bats responded to a high affect intensity test stimulus after experiencing stimuli of low affect intensity, but transferred habituation to a low affect intensity test stimulus after experiencing stimuli of high affect intensity. This transfer of habituation was not due to over-habituation as the bats responded to a frequency-shifted control stimulus. A direct comparison confirmed the asymmetric response behaviour in the reciprocal experiments. Conclusions Thus, the present study provides not only evidence for a discrimination of affect intensity, but also for an evaluation of stimulus salience, suggesting that basic assessment mechanisms involved in the perception of emotion are an ancestral trait in mammals.