Sensitivity to time interval changes in speech and tone conditions

The main goal of the present experiment was to verify whether sensitivity to time interval changes in speech is greater than sensitivity to time interval changes between tones. The 12-syllable sentences were delivered in French (the main language of the participants) or in a foreign language (Slovenian) that was totally unfamiliar to the participants. Two types of sub-sequences were induced within the series of stimuli (sub-sequences in sentences or in tone sequences). Discrimination, as revealed by the Weber fraction in each condition, was much better in the tone conditions than in the speech conditions. Nevertheless, discrimination was excellent in all conditions: Weber fractions below 2% with tones and around 4.5% in the speech conditions. Moreover, the study revealed that familiarity with a particular language does not affect performance and that inducing internal sub-sequences within tone conditions, as opposed to using a series of equal intervals, does not lead to better discrimination. The fact that discrimination is better with tones than with sentences indicates that the extensive training provided by speech does not lead to higher sensitivity to time interval variations than simple tones do. Instead, it seems to indicate that the different acoustical variations in speech reduce the capability to discriminate time interval variations.     

Asymmetrical retention functions for sequences of light flashes or tone bursts in the rat

In Experiment 1, rats were trained in a symbolic delayed matching-to-sample task to discriminate sample stimuli that consisted of sequences of magazine light flashes. The intertrial interval was illuminated by the houselight for Group Light, and it was dark for Group Dark. Retention functions exhibited a choose-many response bias when the delay interval was illuminated by the houselight in both groups, and no consistent response bias when the delay interval was dark. In Experiment 2, rats were trained to discriminate sample stimuli that consisted of sequences of tone bursts. During delay testing, a different tone (i.e., different frequency and location than the sample tone) was present or absent during the delay interval. The retention functions exhibited a significant choose-many bias when tone was present during the delay and a choose-few bias when tone was absent. Asymmetrical retention functions for tone burst and light flash sequences are due to the similarity between the stimulus conditions of the delay interval and the modality of the sequential event being discriminated. These results are consistent with an instructional ambiguity explanation of response biases in memory for number.     

Vowel quality changes produced by surrounding tone sequences

In three experiments, we examined whether energy at the same frequency as one of a vowel's harmonics in the F1 region can be captured by a preceding or following sequence of tones. The position of the /I/-/E/ phoneme boundary along an F1 continuum was used to assess the extent of capture. The first two experiments showed that a sequence of tones at 500 Hz (56-msec duration at 10/sec) can perceptually remove added energy at 500 Hz from a steady vowel (F0 = 125 Hz) that forms part of the sequence. The effect is detectable with one preceding tone, asymptotes with four, and is greater when two tones follow the vowel than when none do. Rising and falling sequences of tones (at 62.5-Hz intervals or at whole-tone intervals) differ in their effect. Falling sequences behave much like constant tones at 500 Hz but with less effect, whereas rising sequences show no evidence of removing the added tone. The second experiment replicated the first and also showed that when the vowel is embedded in a rising or a falling sequence of tones that continue after it, the following tones have no effect. The third experiment suggested that the different effects found with rising versus falling sequences are qualitatively predictable on the basis of the additive effects of their constituent tones rather than by virtue of their contour. The experiments indicated that sequences of repeating tones are much more effective at capturing a harmonic from a vowel than are sequences that follow a simple pattern. This result may reflect the operation of a principle of least commitment in auditory grouping.     

On loudness enhancement of a tone burst by a preceding tone burst

The loudness level of a second tone burst in a monotic burst pair is investigated as a function of the intensity and frequency of the first burst relative to the corresponding variables of the second burst and as a function of the interburst time interval. The loudness level is measured with the help of a third, comparison burst whose frequency is the same as that of the second burst. The results, in connection with preceding results, show beyond any reasonable doubt that loudness effects in pairs of sound bursts are controlled by two perceptual processes: loudness enhancement and loudness summation. The first refers to the loudness of the second burst, the second, to the overall loudness of the burst pair. The time and frequency functions of the two processes are fundamentally different.     

Observing repetitive finger movements modulates response times of auditorily cued finger movements

Our motor and perceptual representations of actions seem to be intimately linked and the human mirror neuron system (MNS) has been proposed as the mediator. In two experiments, we presented biological or non-biological movement stimuli that were either congruent or incongruent to a required response prompted by a tone. When the tone occurred with the onset of the last movement in a series, i.e., it was perceived during the movement presentation, congruent biological stimuli resulted in faster reaction times than congruent non-biological stimuli. The opposite was observed for incongruent stimuli. When the tone was presented after visual movement stimulation, however, no such interaction was present. This implies that biological movement stimuli only affect motor behaviour during visual processing but not thereafter. These data suggest that the MNS is an "online" system; longstanding repetitive visual stimulation (Experiment 1) has no benefit in comparison to only one or two repetitions (Experiment 2).     

Effects of fixed-time shocks and brief stimuli on food-maintained behavior of rats

When a fixed-time schedule of shocks was presented to rats lever pressing for food on a random-interval schedule, a pattern of behavior developed with a high rate of pressing after shock declining to near zero before the next shock was delivered. Once this pattern had stabilized, one-quarter of the shocks were replaced with brief auditory stimuli (tones) in a random sequence. Tone maintained behavior similar to shock, although tone was never paired with shock. Both tone and shocks elicited responding when presented at various times as probe stimuli, and responding was usually totally suppressed if neither stimulus occurred at the beginning of the fixed-time interval. When other stimuli were paired with tone and shock, only those paired with tone gained discriminative control and elicited responding. These findings suggest that stimuli that signal a shock-free, or safe, period will maintain the pattern of behavior generated by shock on a fixed-time schedule. There is a parallel between this phenomenon and the control of behavior on second-order schedules of positive reinforcement with nonpaired brief stimuli.     

Specificity and savings of behavioural habituation over a series of intra- and inter-modal stimuli

A series of four tone stimuli, differing either in tonal frequency or in melody, was presented at the rate of one presentation per day to a group of rats. Habituation was specific to the frequency of simple auditory stimuli and to the melody of patterned stimuli, as shown both by the distraction to stimulus change, and by the trials to habituate to the new stimulus. Savings in habituation occurred when a series of tone stimuli was presented, but was not found for a series of inter-modal stimuli.     

Asymmetry of masking between noise and tone

A pure tone was used to mask narrow and wide bands of noise centered on the frequency of the tone. In a given experimental session, the sound-pressure level (SPL) of the tone was held constant and loudness balances were obtained between a masked and unmasked noise band of equal width. These results are compared to earlier measures of the partial masking of tone by noise. The comparison shows that noise masks a tone more effectively than the tone masks the noise. Although the effect of the tone on a critical band of noise is greater than its effect on either an octave-band noise or wide-band noise, it is considerably smaller than the effect of the noise on the tone. Decreasing the noise bandwidth still further to a subcritical width reduces the asymmetry of masking somewhat, but a difference at high intensities of about 20 dB between the masking effects of an equally intense noise and tone remains. Whether the masker is a tone or noise, masking ceases when the effective energy of the masked and masking stimuli is the same.     

Diotic and dichotic frequency recognition in a single-interval temporal interference procedure

The frequency discriminability of a 70-dB SPL, 20-msec test tone followed 5 msec later by an equally intense 500-msec, 800-Hz interference tone was studied in a single-interval procedure for one diotic condition and three dichotic conditions. The test tone (T) and interference tone (I) were presented the same to both ears (ToIo, diotic condition) and in three dichotic conditions: (1) the interference tone was presented to the right ear (R) and the test tone to the left ear (L) (T_LI_R), (2) the interference tone was presented the same to both ears and the test tone to one ear (TmIo), and (3) the interference tone was presented the same to both ears and the test tone to both ears with an interaural phase reversal (TπIo). The threshold value for test tone frequency discrimination in the diotic temporal interference condition was approximately six times greater than that obtained without an interference tone. The three dichotic temporal interference conditions yielded essentially equivalent threshold values which were approximately 2.4 times that obtained when the test tone was presented without an interference tone. Therefore, although never equaling interference-free conditions, dichotic test tone presentations can improve frequency recognition relative to diotic conditions at intensities well above threshold. It is postulated that this improvement may be due to the spatial separation of test and interfering tones, rather than to possible differences in diotic vs. dichotic subjective intensities. Dichotic-diotic frequency recognition differences did not occur when a 100-msec interval separated the test and interfering tone or when the interfering tone preceded the test tone.     

The effects on eye movements of complexity,novelty, and affective tone

The major purpose of this study was to investigate the effects of stimulus complexity, novelty, and affective tone on the direction of eye movements of male college students. Motion pictures were taken of S’s eye while he viewed pairs of stimuli. In no instance, in any part of the 10 sec. viewing interval, did Ss as a group fixate longer on unpleasant stimuli when they were paired with either pleasant or neutral stimuli; and pleasant stimuli consistently dominated neutral stimuli. Also, novel stimuli and complex stimuli tended to dominate their non-novel and less complex competitors. Differences in instructions were found to markedly affect the magnitude but not the direction of fixation-dominance.     

The slow formation of a pitch percept beyond the ending time of a short tone burst

The discriminability of short tone bursts differing in frequency was measured in terms of the sensitivity index d' as a function of interstimulus interval (ISI). The two stimuli presented on each trial consisted of either 6 or 30 sinusoidal cycles. When the frequency of the first stimulus varied randomly and widely from trial to trial (Experiment 1), discriminability was maximal for an ISI of about 400 msec in the 6-cycles condition and for a significantly longer ISI (of about 1 sec) in the 30-cycles condition. However, when the first stimulus had only two possible frequencies and the second stimulus was fixed (Experiment 2), the optimal ISI appeared to be about 400 msec in both conditions. A final experiment confirmed that, for tone bursts of 30 cycles, the optimal ISI was dependent on the perceptual uncertainty of the first stimulus. These results support the idea that the duration required to perceive the pitch of a sound as accurately as possible may far exceed the duration of the stimulus itself. More importantly, they indicate that the required duration is not a constant.     

Illusory recouplings of onsets and terminations of glide tone components

We present a new auditory illusion, the gap transfer illusion, supported by phenomenological and psychophysical data. In a typical situation, an ascending frequency glide of 2,500 msec with a temporal gap of 100 msec in the middle and a continuously descending frequency glide of 500 msec cross each other at their central positions. These glides move at the same constant speed in logarithmic frequency in opposite directions. The temporal gap in the long glide is perceived as if it were in the short glide. The same kind of subjective transfer of a temporal gap can take place also when the stimulus pattern is reversed in time. This phenomenon suggests that onsets and terminations of glide components behave as if they were independent perceptual elements. We also find that when two long frequency glides are presented successively with a short temporal overlap, a long glide tone covering the whole duration of the pattern and a short tone around the temporal middle can be perceived. To account for these results, we propose an event construction model, in which perceptual onsets and terminations are coupled to construct auditory events and the proximity principle connects these elements.     

The Influence of Retention Interval on the US Preexposure Effect: Changes in Contextual Blocking over Time

A number of studies manipulating the length of the interval between conditioning and testing indicate spontaneous recovery from overshadowing, suggesting that certain instances of overshadowing represent a deficit in memory retrieval rather than a failure of animals to form an association between the overshadowed stimulus and the US. The present series of experiments examined the influence of lengthening the retention interval on blocking, another stimulus selection phenomenon that is typically interpreted as an acquisition deficit. The results indicated that when subjects were tested shortly (3 days) after training conditioning to a taste blocked subsequent conditioning to an odor conditioned in compound with that taste (Experiment 1), whereas prior conditioning to an odor did not block subsequent conditioning to a taste conditioned in compound with that odor (Experiment 2). This pattern of results was essentially unchanged when testing occurred at a longer (21-day) retention interval. However, there was evidence of a US preexposure effect in Experiment 2 when subjects in the US ONLY control condition were tested at the 3-day retention interval, but not when testing occurred 21 days after conditioning. Experiments 3 and 4 examined whether this loss of the US preexposure effect over time might actually represent a change in the degree of contextual blocking as the retention interval is lengthened. Exposure to the conditioning context either during the interval between Phase 1 and Phase 2 of conditioning (Experiment 3) or prior to Phase 1 of conditioning (Experiment 4) alleviated this US preexposure effect suggesting that the loss of the US preexposure effect as the retention interval is lengthened observed in Experiment 2 is due to changes in the degree of blocking by contextual stimuli over time. The results are discussed in terms of differential susceptibility of forgetting of two functional roles played by a contextual stimuli in the current situation-context as a CS and context as a retrieval cue for other CS-US associations.     

Occasion setting of timing behavior

Rats were trained on a temporal switching discrimination, with 2 features, A and B, signaling 2 target conditioned stimuli, x and y; feature offset and target onset were separated by a 5-s feature-target interval, and all target stimulus presentations terminated in a food pellet. The target conditioned stimuli were either short or long (6 or 30 s): Specifically, when signaled by A, x was 6 s and y 30 s, but when x and y were signaled by B, x was 30 s and y 6 s. Trials with 6-s and 30-s targets were termed short and long trials, respectively. Probe tests indicated that the animals correctly anticipated when food was to be delivered on these 2 types of trials. In further testing, the interval between feature offset and target onset was lengthened, to investigate the precise mechanism underlying this behavior. This manipulation did not have a substantial effect on discrimination performance. These results are discussed with reference to theories of occasion setting, timing, and configural learning.     

No time-stretching illusion when a tone is followed by a noise

A sine tone is perceived as longer when it is preceded by a more intense noise than when presented in isolation. This is the time-stretching illusion. We conducted an experiment where the method of constant stimuli was used to examine whether a tone would also be stretched when it was followed by a noise. The duration of a tone was overestimated when it was preceded by a noise, but not when followed by a noise or when located between two consecutive noises. Moreover, the increasing of the noise intensity (from ?6 to +6 dB) relative to the tone intensity resulted in larger overestimations, but only in the condition where a tone was preceded by a noise. In brief, the duration of a tone is stretched when this tone is preceded by a noise and if this tone is not followed by a noise.     

Interference effects in tone memory

Memory for a standard tone in comparison to a subsequent test tone was examined in three experiments with three intervening tones between the standard and test tones. In each trial, the intervening tones were presented from one of seven frequency range and distance from the standard tone conditions. Experiment 1 tone patterns were played at four different presentation rates, and the subjects judged whether the test was higher or lower than the standard. Memory interference effects caused by the different intervening tone conditions could be accounted for by a directional shift in the standard tone memory toward the intervening tones and by a general decrease in the standard tone memory strength with more distant intervening tones. Interference effects were smaller for the rapid presentation rates because the intervening tones formed separate "perceptual streams." Two additional experiments presented the tone patterns in a task requiring the subjects to match a continuously variable tone to their memory of the standard (Experiment 2) and a task requiring them to judge whether the standard and test tones were the "same" or "different" (Experiment 3). These experiments showed large differences in interference effects as a function of the required judgment and the subjects' musical experience.     

Anchor effects on the discrimination of pitch

Two experiments considered the effects of introducing an extreme stimulus (anchor) upon the differential perception of tonal stimuli. In the first experiment, in which Ss rated series stimuli from 1,000 to 2,000 Hz or from 2,000 to 3,000 Hz, the presence of a 750-Hz anchor apparently disrupted discrimination. A second experiment involved testing for a difference threshold (method of limits) in which the standard was a tone of 1,500 Hz. The uncertainty interval (Iu) was larger when the interval between paired stimulus presentations was filled with a 750-Hz tone, again suggesting that discrimination is impaired by the introduction of a low-frequency anchor. Results are discussed in terms of theories relating range extent and discriminability.     

Timing light and tone signals in pigeons

Pigeons' ability to time light and tone stimuli was examined in four experiments. In Experiment 1, two groups of pigeons were trained to discriminate between 2- and 8-s durations of lights or tones and then were transferred to reversal or nonreversal discriminations in the alternate modality. Pigeons learned the light discrimination faster than the tone discrimination and showed immediate positive intermodal transfer from tone to light but not from light to tone. In Experiments 2-4, the peak procedure was used to study birds' timing of 15- and 30-s fixed-interval light and tone signals. Peak times on empty trials under baseline conditions closely approximated the length of fixed-interval signals. When pigeons were tested with time-outs and intermodal switches introduced midway through an empty trial, they tended to reset the timing mechanism and begin timing again from 0 s. With both estimation and production procedures, pigeons were less accurate when timing the tone stimuli than when timing the light stimuli. A comparison of these data with data from timing experiments with rats suggests several possible differences in timing processes between pigeons and rats.     

Effects of a contralateral interference tone on auditory recognition

The effects of a contralateral interference tone on identification of the frequency of a brief signal were investigated. The signal was a 20-reset sinusoid and was the same intensity as the 500-msec interference tone. Changes in frequency discrimination were measured as a function of the temporal intee, al between rdgnal and interference tone. Frequency discrimination was unaffected by the presence of a leading interference torte. However, the addition of a trailing interference tone produced a small (about 15%) decrement in performance relative to discriminability measured in quiet. In contrast to the data and supporting theory of Massaro (1970) percent correct identification did not vary appreciably with intertone interval. The present data suggest that interference effects previously obtained with untrained Os ;are greatly attenuated for well-practiced Ss     

Discrimination of time intervals bounded by tone bursts

Trained listeners had to discriminate, in a four-level 2AFC paradigm, the duration of a time interval bounded by pairs of brief tone bursts. The time intervals ranged from 10 to 100 msec. When the tone-burst markers were similar in their intensity (86 dB SPL) and frequency (1 kHz), the just noticeable time difference was found to be monotonically related to the base interval. On the other hand, when the intensity of the first marker was severely attenuated (by 50 dB) or when a large (2-octave) difference was introduced between the frequencies of the two markers, the time discrimination functions became nonmonotonic. A similar, albeit slight, departure from monotonicity was also achieved by making the second marker much longer than the first (300 msec vs. 10 msec). The nonmonotonicity of these time discrimination functions is compared to the well-documented nonmonotonicity that may be observed for voice onset time (VOT) discrimination functions.