Auditory psychophysical scaling exposure effects: magnitude estimation and cross-modal matching

The purpose of the present study was to investigate possible effects of exposure upon suprathreshold psychological responses when auditory magnitude estimation and cross-modal matching with audition as the standard are conducted within the same experiment. Four groups of 10 subjects each whose over-all age range was 18 to 23 yr. were employed. During the cross-modal matching task the Groups 1 and 2 subjects adjusted a vibrotactile stimulus presented to the dorsal surface of the tongue and the Groups 3 and 4 subjects adjusted a vibrotactile stimulus presented to the thenar eminence of the right hand to match binaurally presented auditory stimuli. The magnitude-estimation task was conducted before the cross-modal matching task for Groups 1 and 3 and the cross-modal matching task was conducted before the magnitude-estimation task for Groups 2 and 4. The psychophysical methods of magnitude estimation and cross-modal matching showed no effect of one upon the other when used in the same experiment.     

Vibrotactile frequency recognition: forward and backward masking effects

Forward and backward vibrotactile recognition masking was investigated in 4 subjects with 240-Hz and 160-Hz targets of 20 ms duration and four 200-Hz masks, using interstimulus intervals (ISIs) ranging from -500 to 500 ms. Two of the masks (short) were 20 ms and two (long) were 200 ms in duration. One of each set of masks was matched in subjective intensity to the targets, but the others were more intense. The range of ISIs over which masking was obtained was comparable to that found by Massaro (1970) with auditory stimuli. Both short masks produced more masking than either long mask except at short ISIs. Larger mask intensities increased masking only at very short ISIs, and longer mask durations increased backward but not forward masking.     

A constant error in the perception of brief temporal intervals

Ss were presented two stimuli of equal duration separated in time. The parrs of stimuli were vibrotactile, auditory, or visual. The Ss adjusted the time between the two stimuli to be equal to the duration of the first stimulus. The results show that for stimulus durations ranging from 100 to 1,200 msec, Ss set the tune between the two stimuli too long and by a constant amount. For vibrotactfle stimuli, the constant was 596 msec; for auditory stimuli, 657 msec; and for visual stimuli, 436 msec. Changing the intensity of the vibrotactile stimuli did not change the size of the constant error. When Ss were presented two tones with a burst of white noise between the tones and adjusted the duration of the white noise to be equal to the duration of the first tone, the white noise was not adjusted too long by a constant amount. The results suggest that there is a constant error in the perception of unfilled relative to filled temporal intervals.     

Exposure effects on the psychophysical scaling methods of magnitude estimation and cross-modal matching for vibrotactile stimulation of the tongue and hand

The purpose of the present study was to investigate possible effects of exposure upon psychophysical scaling responses when vibrotactile magnitude estimation and cross-modal matching are conducted within the same experiment. Four groups of 10 subjects each, with an over-all age range of 18-23 yr., were employed. Groups 1 and 2 performed magnitude estimation for lingual vibrotaction and cross-modal matching with the lingual vibrotactile stimulus as the standard. Group 1 received the magnitude-estimation task first and Group 2 received the cross-modal-matching task first. Groups 3 and 4 performed magnitude estimation for vibrotaction applied to the thenar eminence of the hand and cross-modal matching with the vibrotactile stimulus applied to the thenar eminence of the hand as the standard. Group 3 received the magnitude-estimation task first and Group 4 received the cross-modal-matching task first. The psychophysical scaling methods of magnitude estimation and cross-modal matching showed very little exposure effect of one upon the other when used in the same experiment. Also, magnitude scaling responses tended to increase more rapidly with increases in vibrotactile stimulus intensity when the test site was the thenar eminence of the hand as opposed to the dorsum of the tongue.     

Vibrotactile timing: Are vibrotactile judgements of duration affected by repetitive stimulation?

Timing in the vibrotactile modality was explored. Previous research has shown that repetitive auditory stimulation (in the form of click-trains) and visual stimulation (in the form of flickers) can alter duration judgements in a manner consistent with a “speeding up” of an internal clock. In Experiments 1 and 2 we investigated whether repetitive vibrotactile stimulation in the form of vibration trains would also alter duration judgements of either vibrotactile stimuli or visual stimuli. Participants gave verbal estimates of the duration of vibrotactile and visual stimuli that were preceded either by five seconds of 5-Hz vibration trains, or, by a five-second period of no vibrotactile stimulation, the end of which was signalled by a single vibration pulse (control condition). The results showed that durations were overestimated in the vibrotactile train conditions relative to the control condition; however, the effects were not multiplicative (did not increase with increasing stimulus duration) and as such were not consistent with a speeding up of the internal clock, but rather with an additive attentional effect. An additional finding was that the slope of the vibrotactile psychometric (control condition) function was not significantly different from that of the visual (control condition) function, which replicates a finding from a previous cross-modal comparison of timing.     

Lingual vibrotactile and auditory cross-modal matching: frequency effects

5 subjects matched pairs of auditory and vibrotactile stimuli on intensity, making judgments of suprathreshold magnitudes. Slope values for the 100-Hz cross-modal lingual vibrotactile stimulus-standard frequency condition were steeper than those for 250- or 400-Hz conditions. Slope values became steeper at about 25- to 30-dB SL, so frequency seems an important parameter to control in such research.     

Perception of the duration of auditory and visual stimuli in children and adults

This experiment investigated the effect of modality on temporal discrimination in children aged 5 and 8 years and adults using a bisection task with visual and auditory stimuli ranging from 200 to 800 ms. In the first session, participants were required to compare stimulus durations with standard durations presented in the same modality (within-modality session), and in the second session in different modalities (cross-modal session). Psychophysical functions were orderly in all age groups, with the proportion of long responses (judgement that a duration was more similar to the long than to the short standard) increasing with the stimulus duration, although functions were flatter in the 5-year-olds than in the 8-year-olds and adults. Auditory stimuli were judged to be longer than visual stimuli in all age groups. The statistical results and a theoretical model suggested that this modality effect was due to differences in the pacemaker speed of the internal clock. The 5-year-olds also judged visual stimuli as more variable than auditory ones, indicating that their temporal sensitivity was lower in the visual than in the auditory modality.     

Classical conditioning of the rabbit’s nictitating membrane response to a piezoceramic vibrotactile CS

The present paper reports the development of a transducer system for delivery of a noiseless vibrotactile stimulus that was successfully employed as a conditioned stimulus in classical conditioning of the rabbit’s nictitating membrane response (NMR). In addition, the postasymptotic determination of the relationship between the amplitude and frequency of vibrotactile stimulation and the frequency of conditioned NMRs were found to be monotonically increasing functions. Accordingly, the vibrotactile transducer appears to provide a tractable CS that can be used by itself or in conjunction with visual and auditory stimuli to study a range of issues in animal learning.     

Vibrotactile temporal summation for threshold and suprathreshold levels of stimulation

Threshold measurement and matching procedures were used to determine the amount of temporal summation at threshold and suprathreshold levels of vibrotactile stimulation on the thenar eminence of the hand. The frequency of the stimulus was 25, 40, 80, or 200 Hz. At 25 Hz, temporal summation was absent at all intensity levels. Considerable amounts of temporal summation were observed for 80- and 200-Hz stimuli, although the effects decreased as a function of intensity. At 40 Hz, no temporal summation was observed at threshold, but above threshold, a small amount was observed at all intensity levels. The results support a duplex model of mechanoreception in which one of two receptor systems exhibits temporal summation.     

The effect of skin temperature on vibrotactile sensitivity

The effect of skin temperature on detection of vibrotactile stimuli was measured for vibrations of 30 and 250 Hz. Data for the 250-Hz stimulus supported the results of Weitz (1941), who found that thresholds for 100-, 256-, and 900-Hz vibration varied as a If-shape function of skin temperature with a minimum at about 37°C. Temperature had a negligible effect on sensitivity at 30 Hz. A second experiment examined a range of frequencies between 30 and 250 Hz. Cooling greatly lowered sensitivity only to 150- and 250-Hz stimuli. Warming reduced sensitivity less, but more uniformly across frequencies. It was concluded that cooling may affect vibrotactile thresholds by decreasing the sensitivity of Pacinian corpuscles; the reason for the decrease in sensitivity due to warming is unclear.     

Enhancement and summation in the perception of two successive vibrotactile stimuli

Enhancement and summation were found to be fundamentally different perceptual processes affecting the sensation magnitude of two successive vibrotactile stimuli. Enhancement, defined operationally as an increment in the subjective magnitude of one stimulus due to the presentation of a prior stimulus, and summation, defined as an increment in overall subjective magnitude of the two stimuli, were measured for sinusoidal vibration of the thenar eminence of the hand. The effect of summation was maximum when the two stimuli greatly differed in frequency, whereas maximum enhancement effects were found when both stimuli were close in frequency. The summation effect showed little decay as the interstimulus interval was increased to as much as 500 msec, whereas enhancement effects decayed to zero at approximately 500 msec. Results were similar to those obtained in comparable studies of audition and support the hypothesis that there are at least two distinct information-processing channels for the perception of cutaneous vibration.     

Contralateral enhancement and suppression of vibrotactile sensation

A psychophysical matching procedure was used to measure the effect of a conditioning stimulus on the vibrotactile sensation magnitude of a test stimulus. When both stimuli were applied to the thenar eminence of the same hand, the conditioning stimulus enhanced the sensation magnitude of the test stimulus. Enhancement was also observed when the test stimulus was on the thenar eminence and the conditioning stimulus was either on the contralateral thenar eminence, the ipsilateral middle finger, or the contralateral middle finger. When the conditioning and test stimuli were applied to separate sites, enhancement was maximal when At between the stimuli was 150 msec. At Ate less than 100 msec, suppression was observed. Enhancement and suppression were observed only when the frequencies of the two stimuli were within the same vibrotactile information processing channel.     

The shape of the vibrotactile loudness function: The effect of stimulus repetition and skin-contactor coupling

In the psychophysical literature describing the relationships between physical and psychological magnitudes, as physical intensity increases, perceived intensity often grows much faster near threshold than at higher levels. In this laboratory, however, the loudness curve for sinusoidal vibrotactile stimuli was best fit by a single-limbed function rather than by the expected two-limbed function. In the present study, we measured the growth of vibrotactile loudness of 250-Hz sinusoidal stimuli by the method of absolute magnitude estimation to explore the source of the one- versus two-limbed discrepancy. The number of times that the stimulus was presented was varied, as well as whether the stimulator contacted the skin with constant force or constant penetration. Neither of these manipulations affected the shape of the loudness function consistently. Number of repetitions influenced the shapes of the magnitude estimation functions, but only for a few individuals. Skin-contactor coupling did not affect the shapes of the functions, although the absolute level (vibrotactile loudness) was consistently greater for constant indentation.     

THE INFLUENCE OF AUDITORY STIMULUS INTENSITY ON APPARENT DURATION

B erglund , B., B erglund , U., E kman , G. & F rankenhaeuser , M. The influence of auditory stimulus intensity on apparent duration. Scand J. Psychol ., 1969, 10 21–26.— apparent duration of an auditory signal of 1000 C/S was measured by the method of magnitude estimation. Ten different stimulus intensities ranging from 57 to 104 dB were used in combination with three different durations: 50, 250, and 500 msec. The results showed that the apparent duration of the signal grew as a logarithmic function of stimulus intensity. These results are consistent with the hypothesis relating apparent duration to activation level as well as with results of similar experiments involving electrical and vibrotactile stimulation.     

THE CONTINGENCY OF PERCEPTUAL PROCESSING: Context Modifies Equal-Loudness Relations

Abstract –The relative loudnesses of tones that differ in sound frequency can depend strongly on the stimulus context, that is, on the set of intensity levels m the stimulus ensemble Using a new paradigm, called matching in scaling, this investigation sought to confirm that context modifies loudness relations per se, and not, for example, only overt responses To this end, two experiments revealed that changes in stimulus context differentially affect direct comparisons of loudness of 500-Hz and 2,500-Hz tones, as well as numerical judgments of individual tones—when loudness matches and scaling judgments alike are obtained in the same experimental sessions These contingent effects vary dynamically over time as a function of the recent stimulus history A third experiment revealed analogous effects in a simple matching paradigm, with no numerical judgments at all These findings support the contention that basic properties of loudness perception—grounded in auditory processes often considered "low level"—nevertheless can be deeply contextual     

Vibrotactile--auditory interactions are post-perceptual

Vibrotactile stimuli can elicit compelling auditory sensations, even when sound energy levels are minimal and undetectable. It has previously been shown that subjects judge auditory tones embedded in white noise to be louder when they are accompanied by a vibrotactile stimulus of the same frequency. A first experiment replicated this result at four different levels of auditory stimulation (no tone, tone at detection threshold, tone at 5 dB above threshold, and tone at 10 dB above threshold). The presence of a vibrotactile stimulus induced an increase in the perceived loudness of auditory tones at three of the four values in this range. In two further experiments, a 2-interval forced-choice procedure was used to assess the nature of this cross-modal interaction. Subjects were biased when vibrotaction was applied in one interval, but applying vibrotaction in both intervals produced performance comparable to conditions without vibrotactile stimuli. This demonstrates that vibrotaction is sometimes ignored when judging the presence of an auditory tone. Hence the interaction between vibrotaction and audition does not appear to occur at an early perceptual level.     

Partial masking in electrocutaneous sensation: a model for sensation matching, with applications to loudness recruitment

A model for partial masking and other threshold-elevation effects is presented in the context of a sensation-matching paradigm. The model is applied to an electrocutaneous experiment in which the subjects adjusted stimulus intensity on the right-hand fingertip to match sensation levels of standard stimuli presented to the left fingertip. Concurrent mechanical stimulation on the right fingertip masked sensation magnitude in a way consistent with the model. Similarities between this tactile masking effect and analogous auditory phenomena are explored. When applied to loudness matching, the model describes the general shape of loudness contours and it shows that the steep slopes observed in auditory masking and "recruitment" can be a consequence of a threshold shift alone, without a supranormal growth in loudness. The model also shows that a small response bias can distort plots of sensation matching, leading to the suggestion that some varieties of loudness recruitment may not have a sensory basis.     

Magnitude estimation and magnitude production: stimulus frequency effects on magnitudes of lingual vibrotactile sensation

The methods of magnitude estimation and magnitude production were employed to investigate the effects of stimulus frequency on supra-threshold lingual-vibrotactile sensation-magnitude functions. The method of magnitude estimation was used to obtain numerical judgments of sensation magnitudes for nine stimulus intensities presented to the anterior dorsum of the tongue. The vibrotactile stimulus frequencies employed for 10 subjects (M age = 21.1 yr.) were 100, 250, and 400 Hz. The numerical responses obtained during the magnitude-estimation task were in turn used as stimuli to obtain magnitude-production values for the same three vibrotactile stimulus frequencies. The results appeared to present two suggestions. First, the effects of stimulus frequency on lingual vibrotactile-sensation magnitudes may be dependent on the psychophysical method used in any particular experiment. Second, lingual-vibrotactile magnitude-estimation scales may demonstrate asymptotic growth functions above about 25 dB sensation level. The limitation in the growth of sensation magnitude occurred for all three vibrotactile stimulus frequencies employed.     

Response summation to a compound stimulus in a context of choice

Key pecks by two groups of pigeons were reinforced on concurrent schedules. For group Ē, pecks were reinforced during either a visual or an auditory stimulus; for group E, an additional, extinction component was available, during which both visual and auditory stimuli were absent. After training, both groups were given a compound test to measure preference among four stimuli, the three used in training plus a compound of the visual and auditory stimulus. Group E showed preference for the compound, emitting more pecks and spending more time in this stimulus than in other stimuli. Group Ē showed no preference between the compound and visual stimulus, nor between the auditory stimulus and the absence of both stimuli, but preferred the former pair over the latter pair of stimuli.     

Reception of Morse code through motional, vibrotactile, and auditory stimulation

The potential for communication through the kinesthetic aspect of the tactual sense was examined in a series of experiments employing Morse code signals. Experienced and inexperienced Morse code operators were trained to identify Morse code signals that were delivered as sequences of motional stimulation through up-down displacements (roughly 10 mm) of the fingertip. Performance on this task was compared with that obtained for both vibrotactile and acoustic presentation of Morse code using a 200-Hz tone delivered either to the fingertip through a minishaker or diotically to the two ears under headphones. For all three modalities, the ability to receive Morse code was examined as a function of presentation rate for tasks including identification of single letters, random three-letter sequences, common words, and sentences. Equivalent word-rate measures (i.e., product of percent correct scores and stimulus presentation rate) were nearly twice as high for auditory presentation as for vibrotactile stimulation, which in turn was about 1.3 times that for motional stimulation. The experienced subjects outperformed the inexperienced subjects by amounts that increased with task complexity. For example, the former were able to receive sentences at 18 words/min with motional stimulation, whereas the latter, following 75 h of training, were unable to perform this task. The present results and those of other research with tactual communication systems are compared, particularly regarding estimates of information-transfer rates.