Echoic memory and language perception

The purpose of this study was to analyze asymmetry in echoic memory as a relevant factor in language perception. Two experimental procedures were used: the presentation of temporally segmented words in fragments of 40, 80, 120 and 240 msec, separated by intervals of 40, 80, 120 and 240 msec, similar to the procedures used by A. W. F. Huggins (1975, Perception & Psychophysics, 18, 149-157); the presentation of two tones of short duration, "high" and "low," followed by an interference tone equivalent to the mean frequency of the two tones, closely following the procedure used by D. W. Massaro (1975, in D.W. Massaro (Ed.), Understanding language, New York: Academic Press). A stereophonic tape recorder was used as follows: one channel was employed for the presentation of the words or tones while, through the other channel, the subject received a white noise equivalent in intensity. All subjects carried out the task twice (right ear, left ear) and the order of presentation was counterbalanced. Only the first task showed differences between ears. Implications of the results are analyzed.     

Feature processing during high-rate auditory selective attention

Auditory event-related brain potentials (ERPs) and reaction times were, analyzed in a selective attention task in which subjects attended to tone pips presented at high rates-Xinterstimulua intervals [ISIs] of 40-200 msec). Subjects responded to infrequent target tones of a specified frequency (250 or 4000 Hz) and location (left or right ear) that were louder than otherwise identical tones presented randomly to the left and right ears. Negative difference (Nd) waves were isolated by subtracting ERPs to tones with no target features from ERPs to the same tones when they shared target location, frequency, or both frequency and location cues. Nd waves began 60-70 msec after tone onset and lasted until 252–350 msec after tone onset, even for tones with single attended cues. The duration of Nd waves exceeded the ISIs between successive tones, implying that several stimuli underwent concurrent analysis. Nd waves associated with frequency processing had scalp distributions different from those associated with location processing, implying that the features were analyzed in distinct cortical areas. Nd waves specific to auditory feature conjunction were isolated. These began at latencies of 110–120 msec, some 30-40 msec after the Nds to single features. The relative timing of the different Nd waves suggests that auditory feaure conjunction begins after a brief parallel analysis of individual features but before feature analysis is complete.     

Effect of masker level on infants' detection of tones in noise

In adult listeners, the signal-to-noise ratio at masked threshold remains constant with increases in masker level over a wide range of stimulus conditions. This relationship was examined in 7-month-old infants by obtaining masked thresholds for .5- and 4-kHz tones presented in four levels of continuous masking noise. Adults were also tested for comparison. Masker spectrum levels ranged from 5 to 35 dB/Hz for .5-kHz tones, and from -5 to 25 dB/Hz for 4-kHz stimuli. Thresholds were determined for stimuli of both 10 and 100 msec in duration. The results indicated that infants' performance was more adult-like for 4-kHz stimuli. Although mean thresholds for both 10- and 100-msec, 4-kHz tones were approximately 7 dB higher in infants than in adults, E/N0 at threshold remained essentially constant over the 30-dB range of maskers employed. By contrast, infants' thresholds for .5-kHz tones were exceptionally high at lower levels of the masker. Threshold E/N0 decreased significantly as masker level increased from 5 to 35 dB/Hz, and this decrease was significantly greater for 10- than for 100-msec stimuli. Temporal summation of .5-kHz tones, measured as the difference between thresholds obtained at the two signal durations, was greater for infants than for adults at low levels of the masker. However, because infants' thresholds improved more rapidly with level for 10- than for 100-msec tones, age differences in temporal summation were no longer significant when masker spectrum level was 35 dB/Hz. These results suggest that the relationship between signal-to-noise ratio at masked threshold and level of the masker is dependent on both signal frequency and duration during infancy.     

Effect of masker level on infants’ detection of tones in noise

In adult listeners, the signal-to-noise ratio at masked threshold remains constant with increases in masker level over a wide range of stimulus conditions. This relationship was examined in 7-month-old infants by obtaining masked thresholds for .5- and 4-kHz tones presented in four levels of continuous masking noise. Adults were also tested for comparison. Masker spectrum levels ranged from 5 to 35 dB/Hz for .5-kHz tones, and from ?5 to 25 dB/Hz for 4-kHz stimuli. Thresholds were determined for stimuli of both 10 and 100 msec in duration. The results indicated that infants’ performance was more adultlike for 4-kHz stimuli. Although mean thresholds for both 10- and 100-msec, 4-kHz tones were approximately 7 dB higher in infants than in adults, E/N₀ at threshold remained essentially constant over the 30-dB range of maskers employed. By contrast, infants’ thresholds for .5-kHz tones were exceptionally high at lower levels of the masker. Threshold E/N0 decreased significantly as masker level increased from 5 to 35 dB/Hz, and this decrease was significantly greater for 10- than for 100-msec stimuli. Temporal summation of .5-kHz tones, measured as the difference between thresholds obtained at the two signal durations, was greater for infants than for adults at low levels of the masker. However, because infants’ thresholds improved more rapidly with level for 10- than for 100-msec tones, age differences in temporal summation were no longer significant when masker spectrum level was 35 dB/Hz. These results suggest that the relationship between signal-to-noise ratio at masked threshold and level of the masker is dependent on both signal frequency and duration during infancy.     

Identification of temporal order within auditory sequences

Unpracticed Ss reported the order of sounds in sequences consisting of either three or four successive items repeated over and over without pause. With unrelated sounds each lasting 200 msec, correct reports of order were at chance level for oral responses and for card-ordering responses (each card bearing the name of one sound). The sequences with four unrelated items were studied in greater detail, and the threshold for identification was found to be 670 msec with oral responses and 300 msec with card-ordering responses. When two related sounds (tones) were used in four-item sequences, correct card-ordering was possible at 200 msec per item when the tones were temporally contiguous, but was not possible at this duration when the tones were separated by nonrelated sounds. Some special rules governing auditory sequence identification were suggested, and implications for theories of auditory perception discussed.     

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.     

Pattern identification of pure tones and frequency glides by untrained listeners

Six subjects identified the order of four-event sequences. Contiguous pure tones (713, 1,031, 1,209, and 1,514 Hz in permuted orders) were presented by earphones at 40 dB SL, with individual events Itones) from 20, to 40, 60, and 300 msec in duration. Again, silent intervals of 20 or 60 msec were inserted among tones of 20 or 40 msec duration. Finally, the pure tones of 713 and 1,209 Hz were combined, in any four-event sequence, with two glissandi chosen from 466 to 714 Hz, from 714 to 1,208 Hz, and their mirror reversals. The temporal and frequency continuity both of tonal and of glissando-plus-tonal sequences affected the identification of sequential order. Degraded performance in the glissando-plus-tonal condition was attributed partially to a subjective experience of pitch blurring. The inclusion of silent intervals in the sequences of the shorter pure-tone durations improved identification performance to that of contiguous sequences of equal overall duration, i.e., adding silent processing time was as efficacious as increasing by the same amount the duration of the individual frequency event.     

Within-modality and cross-modality attentional blinks in a simple discrimination task

Following up on studies of the "attentional blink," we studied interference between successive target stimuli in visual and auditory modalities. In each experiment, stimuli were two tones and four dots, simultaneously presented for 1,800 msec. Targets were brief intensity changes in either a tone or a dot. Subjects gave unspeeded responses. In four experiments, our results showed interference between targets in the same modality, but not across modalities. We conclude that, under our experimental conditions, restrictions in concurrent target identification are largely modality specific.     

Identification and discrimination of sweep formants

Earlier identification experiments with sweep tones are repeated with rising and falling single formant (band) sweeps, with durations ranging from 15 to 40 msec and sweep rates from 0 to 40 oct/sec. Steady-state portions of 100-msec duration are then added to the sweeps. The general conclusions are that the tendency to perceive level and slightly rising tones as falling, which was such a prominent feature of the earlier results, disappears as the stimuli become more complex, and that sweep discrimination seems to be a function of the difference between the initial and the final frequency of a sweep.     

Why are damped sounds perceived as shorter than ramped sounds?

Hearing is the most accurate sense for perceiving duration. However, rarely it produces inaccurate estimates of duration, for example when it compares the subjective duration of tones that are increasing in intensity over time (i.e., ramped) with that of tones that are decreasing in intensity over time (i.e., damped). The literature reports that the damped tones are perceived as much being shorter than the ramped tones of the same length. The short subjective duration of damped tones may originate from a decay suppression mechanism that parses the source-informative part of many natural sounds (i.e., the beginning) from the less informative part of them (the decay): listeners may interpret the tail of damped tones like an echo or like the decay portion of an impact sound and exclude it from the account of the duration of the tone. In the natural soundscape, the tail of sounds produced in reverberant environments and the tail of impact sounds have a frequency content that is constant throughout the sound’s duration. Here, the carriers used for ramped and damped sounds were a tone constant in frequency and a tone modulated in frequency. The frequency modulation was introduced to prevent the listener from interpreting the tail of these tones as the result of reverberation or the decay portion of an impact sound. Frequency constant damped tones were largely underestimated in duration whereas frequency modulated ones were not (or were only slightly), demonstrating that the decay suppression mechanism is a worthy explanation for the short subjective duration of damped tones.

     

Studies in auditory timing: 1. Simple patterns

Listeners' accuracy in discriminating one temporal pattern from another was measured in three psychophysical experiments. When the standard pattern consisted of equally timed (isochronic) brief tones, whose interonset intervals (IOIs) were 50, 100, or 200 msec, the accuracy in detecting an asynchrony or deviation of one tone in the sequence was about as would be predicted from older research on the discrimination of single time intervals (6%-8% at an IOI of 200 msec, 11%-12% at an IOI of 100 msec, and almost 20% at an IOI of 50 msec). In a series of 6 or 10 tones, this accuracy was independent of position of delay for IOIs of 100 and 200 msec. At 50 msec, however, accuracy depended on position, being worst in initial positions and best in final positions. When one tone in a series of six has a frequency different from the others, there is some evidence (at IOI = 200 msec) that interval discrimination is relatively poorer for the tone with the different frequency. Similarly, even if all tones have the same frequency but one interval in the series is made twice as long as the others, temporal discrimination is poorer for the tones bordering the longer interval, although this result is dependent on tempo or IOI. Results with these temporally more complex patterns may be interpreted in part by applying the relative Weber ratio to the intervals before and after the delayed tone. Alternatively, these experiments may show the influence of accent on the temporal discrimination of individual tones.     

Precision and accuracy in the reproduction of simple tone sequences

In four experiments we investigated the precision and accuracy with which amateur musicians are able to reproduce sequences of tones varied only temporally, so as to have tone and rest durations constant over sequences, and the tempo varied over the musically meaningful range of 5-0.5 tones per second. Experiments 1 and 2 supported the hypothesis of attentional bias toward having the attack moments, rather than the departure moments, precisely times. Experiment 3 corroborated the hypothesis that inaccurate timing of short interattack intervals is manifested in a lengthening of rests, rather than tones, as a result of larger motor activity during the reproduction of rests. Experiment 4 gave some support to the hypothesis that the shortening of long interattack intervals is due to mnemonic constraints affecting the rests rather than the tones. Both theoretical and practical consequences of the various findings, particularly with respect to timing in musical performance, are discussed.     

Time course of chord priming

The time course of chord priming was explored in four experiments. In chord priming, a chord (a typical combination of simultaneously sounded tones) primes other chords that are musically related. In the present study, the prime duration and the stimulus onset asynchrony (SOA) between the prime chord and the chord to be judged were varied. Priming occurred at an SOA and prime duration as short as 50 msec, the shortest tested. When the prime duration was held constant at 50 msec, priming occurred at an SOA as long as 2,500 msec, the longest tested, and the magnitude of the priming effect did not diminish. To eliminate a possible role of sensory memory in maintaining the priming effect during the silence following the prime, a 250-msec noise mask was presented immediately following the 50-msec prime. The interpolated noise mask did not eliminate priming, thereby supporting the view that chord priming is the consequence of associative activation.     

Time course of chord priming.

The time course of chord priming was explored in four experiments. In chord priming, a chord (a typical combination of simultaneously sounded tones) primes other chords that are musically related. In the present study, the prime duration and the stimulus onset asynchrony (SOA) between the prime chord and the chord to be judged were varied. Priming occurred at an SOA and prime duration as short as 50 msec, the shortest tested. When the prime duration was held constant at 50 msec, priming occurred at an SOA as long as 2,500 msec, the longest tested, and the magnitude of the priming effect did not diminish. To eliminate a possible role of sensory memory in maintaining the priming effect during the silence following the prime, a 250-msec noise mask was presented immediately following the 50-msec prime. The interpolated noise mask did not eliminate priming, thereby supporting the view that chord priming is the consequence of associative activation.     

The perception of pure and mistuned musical fifths and major thirds: Thresholds for discrimination,beats, and identification

In Experiment 1, the discriminability of pure and mistuned musical intervals consisting of simultaneously presented complex tones was investigated. Because of the interference of nearby harmonics, two features of beats were varied independently: (1) beat frequency, and (2) the depth of the level variation. Discrimination thresholds (DTs) were expressed as differences in level (AL) between the two tones. DTs were determined for musical fifths and major thirds, at tone durations of 250, 500, and 1,000 msec, and for beat frequencies within a range of .5 to 32 Hz. The results showed that DTs were higher (smaller values of ΔL) for major thirds than for fifths, were highest for the lowest beat frequencies, and decreased with increasing tone duration. Interaction of tone duration and beat frequency showed that DTs were higher for short tones than for sustained tones only when the mistuning was not too large. It was concluded that, at higher beat frequencies, DTs could be based more on the perception of interval width than on the perception of beats or roughness. Experiments 2 and 3 were designed to ascertain to what extent this was true. In Experiment 2, beat thresholds (BTs) for a large number of different beat frequencies were determined. In Experiment 3, DTs, BTs, and thresholds for the identification of the direction of mistuning (ITs) were determined. For mistuned fifths and major thirds, sensitivity to beats was about the same. ITs for fifths and major thirds were not significantly different; deviations from perfect at threshold ranged from about 20 to 30 cents. Comparison of the different thresholds revealed that DTs are mainly determined by sensitivity to beats. Detailed analysis, however, indicated that perception of interval width is a relevant aspect in discrimination, especially for the fifths.     

Infants’ detection of increments in low- and high-frequency noise

A visually reinforced operant paradigm was employed to examine the relationship between the difference limen (DL) for intensity and level of the standard during infancy. In Experiment 1,7-month-old infants and adults detected increments in continuous noise presented via headphones at each of four levels ranging from 28 to 58 dB SPL. Noise stimuli were 2-octave bands centered at either 400 or 4000 Hz, and increments were 10 and 100 msec in duration. Infants’ DLs were significantly larger than those of adult subjects and significantly larger for low- than for high-frequency stimuli. For the high-frequency noise band, infants’ DLs were generally consistent with Weber’s law,remaining essentially constant for standards higher than 28 dB SPL (3 dB SL) for 100-msec increments and 38 dB SPL (13 dB SL) for 10-msec increments. For low-frequency noise, infants’ absolute thresholds were exceptionally high, and sensation levels of the standards were too low to adequately describe the relationship. In Ex-periment 2, 7-month-old infants detected 10- and 100-msec increments in 400-Hz noise stimuli presented in sound field. Infants’ low-frequency DLs were large at low intensities and decreased with increases in level of the standard up to at least 30 dB SL. For both low- and high-frequency noise, the difference between DLs for 10- and 100-msec increments tended to be large at low levels of the standard and to decrease at higher levels. These results suggest that the relationship between the DL and level of the standard varies with both stimulus frequency and duration during infancy. However, stimulus-dependent immaturities in increment detection may be most evident at levels within approximately 30 dB of absolute threshold.     

Impaired short temporal interval discrimination in a dyslexic adult

The ability to discriminate short temporal intervals was examined in a dyslexic adult (E.C.) and six matched controls. Listeners had to decide whether the second interval was shorter or longer than a standard (target) interval. Each interval was defined as the silent duration between two successive brief tones. Eight target intervals were used, ranging from 100 to 1,200 ms in duration. At each target interval, the differential threshold (DL) for duration was assessed, with the use of an adaptive psychophysical procedure. The results show that E.C.'s differential threshold values were much larger than those of controls. Moreover, the slope estimates covering the duration range from 100 to 800 ms indicated that in comparison to controls, E.C.'s differential threshold increased dramatically as the target duration increased. Thus her timing impairment becomes more pronounced with increasing duration. This timing deficit is consistent with other studies that have found temporal processing deficits associated with dyslexia.     

Differences in duration discrimination of filled and empty auditory intervals as a function of base duration

In the present experiments, participants were presented with two time intervals that were marked by auditory signals, and their task was to decide which of the two was longer in duration. In Experiment 1, the base durations were 50 and 1,000msec, whereas in Experiment 2, seven different base durations ranging from 50 to 1,000 msec were employed. It was found that filled intervals (continuous tones) were discriminated more accurately than empty intervals (with onset and offset marked by clicks) at the 50-msec base duration, whereas no performance differences could be shown for longer ones. The findings are consistent with the notion of a unitary timing mechanism that governs the timing of both filled and empty auditory intervals, independent of base durations. A likely conceptual framework that could explain better performance with filled as compared with empty intervals represents an information-processing model of interval timing that evolved from scalar timing theory. According to this account, a performance decrement observed with empty intervals may be due to a misassignment of pulses generated by an internal pacemaker.     

The perception of temporal deviations in isochronic patterns

In a study of perceptual synchronization with an isochronic sequence, subjects were given the following task: They heard an isochronic sequence of tones in which the last interval was either correct or too long. Their task was to detect irregularity. The independent variables were the number of tones heard and the time interval between them. The dependent variable was the difference limen (DL) for the detectability of the irregularity. Two experiments were performed in this study, differing in the way in which the trials were blocked: In Experiment 1, stimuli with the same period were presented in blocks, whereas in Experiment 2, the period of the stimulus was randomized. The results show that in Experiment 1 the number of tones in the stimulus did not affect the detectability of the anisochrony. In Experiment 2, the number of the DL was a decreasing function of the number of tones heard. Moreover, the decrease of the DL was larger than one would expect from a simple model of information integration, which assumes that subjects improve their performance by averaging their percepts of the first intervals in the sequence. The difference between this task and experiments on the discrimination of temporal intervals is discussed.     

The slippery context effect in psychophysics: intensive, extensive, and qualitative continua.

When subjects gave magnitude estimates of 500- and 2500-Hz tones at various SPLs, they judged a 500-Hz tone of 60 dB to be as loud as a 2500-Hz tone of 57 dB in one context (low SPLs at 500 Hz, high SPLs at 2500 Hz), but as loud as a 2500-Hz tone at 40 dB in another context (high SPLs at 500 Hz, low at 2500 Hz) (Marks, 1988). Such shifts in matches derived from judgments of multidimensionally varying stimuli are termed slippery context effects. The present set of seven experiments showed that slippery effects were absent from judgments of pitch of tones at different loudnesses, duration of tones at different pitches, and length of lines at different colors, though a small effect emerged in judgments of duration of tones and lights. Slippery context effects were substantial when subjects gave magnitude estimates of loudness of 500- and 2500-Hz tones under conditions in which the pitch at each trial either was cued visually beforehand or could be known through the regular stimulus sequence, and with instructions to make absolute magnitude estimates. The results are consistent with the view that slippery context effects occur automatically and "preattentively."