The auditory redundant signals effect: An influence of number of stimuli or number of percepts?

In two experiments, we examined simple reaction times (RTs) for detection of the onsets and offsets of auditory stimuli. Both experiments assessed the redundant signals effect (RSE), which is traditionally defined as the reduction in RT associated with the presentation of two redundant stimuli, rather than a single stimulus. In Experiment 1, with two identical tones presented via headphones to the left ear, right ear, or both, no RSE was found in responding to tone onsets, but a large RSE was found in responding to their offsets. In Experiment 2, with a pure tone and white noise as the two stimulus alternatives, RSEs were found for responding to both onsets and offsets. The results support the notion that the occurrence of an RSE depends on the number of percepts, rather than the number of stimuli, and on the requirement to respond to stimulus onsets versus offsets. The parallel grains model (Miller & Ulrich, 2003) provides one possible account of this pattern of results.     

Pure-tone perception and ear advantages in dichotic listening

A same-different matching task was used to investigate how subjects perceived a dichotic pair of pure tones. Pairs of stimulus tones in four frequency ranges (center frequencies of 400–1,700 Hz), with separations between 40 and 400 Hzt were tested. Five types of test tones were matched to the stimulus pair: the stimulus pair presented again (control) or crossed over (same tones, different ears), the geometric mean of the two tones, or a binaural tone of the low or high tone of the pair. In the lowest frequency range and the highest with maximum separation, the crossed-over test tones were perceived as different from the same stimulus tones. A bias for perceiving the higher tone of a pair was evident in the frequency ranges with separations of 40-200 Hz. In the lowest frequency range, the bias was for perceiving the higher tone in the right ear. This restricted ear advantage in the perception of pure tones was not significantly related to the right-ear advantage in dichotic word monitoring.     

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.     

Effects of response task and accessory stimuli on redundancy gain: tests of the hemispheric coactivation model

Two experiments tested predictions of the hemispheric coactivation model for redundancy gain (J. O. Miller, 2004). Simple reaction time was measured in divided attention tasks with visual stimuli presented to the left or right of fixation or redundantly to both sides. Experiment 1 tested the prediction that redundancy gain--the decrease in reaction time when 2 stimuli are presented rather than 1--should increase when the response requires a greater degree of bilateral control by both hemispheres. In different blocks, the response was made with the left hand, the right hand, or both hands simultaneously. In accordance with the model, redundancy gain was larger with bimanual than with unimanual responses. Experiment 2 tested and found support for the prediction that redundancy gain should decrease when both hemispheres are activated by an irrelevant auditory accessory stimulus. Thus, the results support the hemispheric coactivation model.     

Frequency-shift detectors bind binaural as well as monaural frequency representations

Previous psychophysical work provided evidence for the existence of automatic frequency-shift detectors (FSDs) that establish perceptual links between successive sounds. In this study, we investigated the characteristics of the FSDs with respect to the binaural system. Listeners were presented with sound sequences consisting of a chord of pure tones followed by a single test tone. Two tasks were performed. In the "present/absent" task, the test tone was either identical to one of the chord components or positioned halfway in frequency between two components, and listeners had to discriminate between these two possibilities. In the "up/down" task, the test tone was slightly different in frequency from one of the chord components and listeners had to identify the direction (up or down) of the corresponding shift. When the test tone was a pure tone presented monaurally, either to the same ear as the chord or to the opposite ear, listeners performed the up/down task better than the present/absent task. This paradoxical advantage for directional frequency shifts, providing evidence for FSDs, persisted when the test tone was replaced by a dichotic stimulus consisting of noise but evoking a pitch sensation as a consequence of binaural processing. Performance in the up/down task was similar for the dichotic stimulus and for a monaural narrow-band noise matched in pitch salience to it. Our results indicate that the FSDs are insensitive to sound localization mechanisms and operate on central frequency representations, at or above the level of convergence of the monaural auditory pathways.     

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.     

Referential coding contributes to the horizontal SMARC effect

The present study tested whether coding of tone pitch relative to a referent contributes to the correspondence effect between the pitch height of an auditory stimulus and the location of a lateralized response. When left-right responses are mapped to high or low pitch tones, performance is better with the high-right/low-left mapping than with the opposite mapping, a phenomenon called the horizontal SMARC effect. However, when pitch height is task irrelevant, the horizontal SMARC effect occurs only for musicians. In Experiment 1, nonmusicians performed a pitch discrimination task, and the SMARC effect was evident regardless of whether a referent tone was presented. However, in Experiment 2, for a timbre-judgment task, nonmusicians showed a SMARC effect only when a referent tone was presented, whereas musicians showed a SMARC effect that did not interact with presence/absence of the referent. Dependence of the SMARC effect for nonmusicians on a reference tone was replicated in Experiment 3, in which judgments of the color of a visual stimulus were made in the presence of a concurrent high- or low-pitched pure tone. These results suggest that referential coding of pitch height is a key determinant for the horizontal SMARC effect when pitch height is irrelevant to the task.     

Impact of contingency manipulations on accessory stimulus effects

Accessory tone stimuli facilitate response performance despite being irrelevant for the current task. In order to investigate which processes are affected by accessory stimuli, we presented accessory tones in a simple response time (RT) task while varying the contingencies between accessory stimulation and either responses(Experiment 1) or stimulus conditions (Experiment 2). Accessory tones speeded up responding to a larger degree when they were conjointly presented within go compared with no-go trials. In contrast, contingency variation with stimulus conditions did not alter the impact of accessory stimuli. Additionally, accessory tones increased response force. Thus, we conclude that in simple RT tasks accessory tones influence response-related stages such as response selection and response execution rather than perceptual processes.     

Visual dominance in the pigeon

In Experiment 1, three pigeons were trained to obtain grain by depressing one foot treadle in the presence of a 746-Hertz tone stimulus and by depressing a second foot treadle in the presence of a red light stimulus. Intertrial stimuli included white light and the absence of tone. The latencies to respond on auditory element trials were as fast, or faster, than on visual element trials, but pigeons always responded on the visual treadle when presented with a compound stimulus composed of the auditory and visual elements. In Experiment 2, pigeons were trained on the auditory-visual discrimination task using as trial stimuli increases in the intensity of auditory or visual intertrial stimuli. Again, pigeons showed visual dominance on subsequent compound stimulus test trials. In Experiment 3, on compound test trials, the onset of the visual stimulus was delayed relative to the onset of the auditory stimulus. Visual treadle responses generally occurred with delay intervals of less than 500 milliseconds, and auditory treadle responses generally occurred with delay intervals of greater than 500 milliseconds. The results are discussed in terms of Posner, Nissen, and Klein's (1976) theory of visual dominance in humans.     

Auditory negative priming in speeded reactions and temporal order judgements

Two experiments are reported that demonstrate negative priming for auditory stimuli. Reaction times and temporal order judgements were used as the dependent measures in Experiments 1 and 2, respectively. In Experiment 1, participants classified tones presented to one ear as wind or string instruments while ignoring tones presented to the other ear. The task was identical for both the prime and the subsequent probe presentations. Probe reactions were slower for previously ignored tones than for tones that had not occurred during the prime presentation. Probe reactions to previously attended tones were faster than reactions to nonrepeated tones. In Experiment 2, the probe reactions were replaced by temporal order judgements. The probability of accepting a tone as antecedent was lower for previously ignored primes than for new tones. No difference was observed between previously attended and new tones. The results are compatible with the conclusion that distractor inhibition is a necessary component of the processes that bring about observable negative priming phenomena.     

Effects of laterality and pitch height of an auditory accessory stimulus on horizontal response selection: The Simon effect and the SMARC effect

In the present article, we investigated the effects of pitch height and the presented ear (laterality) of an auditory stimulus, irrelevant to the ongoing visual task, on horizontal response selection. Performance was better when the response and the stimulated ear spatially corresponded (Simon effect), and when the spatial—musical association of response codes (SMARC) correspondence was maintained—that is, right (left) response with a high-pitched (low-pitched) tone. These findings reveal an automatic activation of spatially and musically associated responses by task-irrelevant auditory accessory stimuli. Pitch height is strong enough to influence the horizontal responses despite modality differences with task target.     

On the interplay of visuospatial and audiotemporal dominance: Evidence from a multimodal kappa effect

When participants judge multimodal audiovisual stimuli, the auditory information strongly dominates temporal judgments, whereas the visual information dominates spatial judgments. However, temporal judgments are not independent of spatial features. For example, in the kappa effect, the time interval between two marker stimuli appears longer when they originate from spatially distant sources rather than from the same source. We investigated the kappa effect for auditory markers presented with accompanying irrelevant visual stimuli. The spatial sources of the markers were varied such that they were either congruent or incongruent across modalities. In two experiments, we demonstrated that the spatial layout of the visual stimuli affected perceived auditory interval duration. This effect occurred although the visual stimuli were designated to be task-irrelevant for the duration reproduction task in Experiment 1, and even when the visual stimuli did not contain sufficient temporal information to perform a two-interval comparison task in Experiment 2. We conclude that the visual and auditory marker stimuli were integrated into a combined multisensory percept containing temporal as well as task-irrelevant spatial aspects of the stimulation. Through this multisensory integration process, visuospatial information affected even temporal judgments, which are typically dominated by the auditory modality.     

The effect of exogenous spatial attention on auditory information processing

This study investigated the effect of exogenous spatial attention on auditory information processing. In Experiments 1, 2 and 3, temporal order judgment tasks were performed to examine the effect. In Experiment 1 and 2, a cue tone was presented to either the left or right ear, followed by sequential presentation of two target tones. The subjects judged the order of presentation of the target tones. The results showed that subjects heard both tones simultaneously when the target tone, which was presented on the same side as the cue tone, was presented after the target tone on the opposite side. This indicates that spatial exogenous attention was aroused by the cue tone, and facilitated subsequent auditory information processing. Experiment 3 examined whether both cue position and frequency influence the resulting information processing. The same effect of spatial attention was observed, but the effect of attention to a certain frequency was only partially observed. In Experiment 4, a tone fusion judgment task was performed to examine whether the effect of spatial attention occurred in the initial stages of hearing. The result suggests that the effect occurred in the later stages of hearing.     

Task integration as a factor in secondary-task effects on sequence learning

In several studies it has been found that implicit sequence learning is impaired by the concurrent performance of a secondary task. In most studies the task was to count high-pitched tones when high-pitched and low-pitched tones were presented in a random sequence. In this paper the hypothesis is examined that dual-task interference in the particular combination of tasks results from task integration, in particular from the learning of an integrated visual-auditory sequence in which every second (auditory) element is random. Instead of the tone-counting task a similar go/no-go task was used in which foot responses to high-pitched tones were performed. In Exp. 1 the sequence of tones was random in one condition, but in two other conditions repeated tone sequences of 5 and 6 elements were combined with visual sequences of 6 elements. Under dual-task test conditions, implicit learning of the visual as well as the auditory sequences was better with the auditory sequence of 6 elements than of 5 elements, while under single-task test conditions the nature of the tone sequence had no effect. In Exp. 2 the superior implicit learning with the 6-element sequence was replicated with different test procedures in which either the visual or auditory sequence was changed to random or in which the two sequences remained intact but were shifted by one element relative to each other. Randomization of the visual or auditory sequences not only impaired visual or auditory RT, respectively, but also impaired RT to stimuli in the other modality, and this cross-modal effect was almost as strong as the intra-modal effect of randomization. Finally, in Exp. 3 it was shown that integrated visual-auditory sequences are learned only when responses to both of them are required, but not when the tones can be neglected. These results are consistent with a conception of implicit learning as (at least partly) a basic and nonselective type of learning of all potentially behaviorally relevant relations between stimuli in the environment and one's own actions.     

The effects of contralateral noise on reaction time to monaural stimuli

Experiment I measured reaction time (RT) to monaural tones of six frequencies presented along with white noise to the contralateral ear. RT with the hand ipsilateral to the stimulus was an average of 9.63 msec faster than RT with the contralateral hand. Contralateral RT was significantly affected by the stimulus frequency. Experiment II measured ipsilateral and contralateral RT to monaural tones with and without contralateral noise. Noise-on results agreed with the results of Experiment I, while noise-off results showed no difference between ipsilateral and contralateral RT. No right-ear advantage was found. The ipsilateral-contralateral RT difference found with noise on is interpreted as being due to callosal transmission time as well as other factors. The finding of no right-ear advantage is discussed in relation to other studies which did report a right-ear advantage.     

Sound enhances visual perception: cross-modal effects of auditory organization on vision

Six experiments demonstrated cross-modal influences from the auditory modality on the visual modality at an early level of perceptual organization. Participants had to detect a visual target in a rapidly changing sequence of visual distractors. A high tone embedded in a sequence of low tones improved detection of a synchronously presented visual target (Experiment 1), but the effect disappeared when the high tone was presented before the target (Experiment 2). Rhythmically based or order-based anticipation was unlikely to account for the effect because the improvement was unaffected by whether there was jitter (Experiment 3) or a random number of distractors between successive targets (Experiment 4). The facilitatory effect was greatly reduced when the tone was less abrupt and part of a melody (Experiments 5 and 6). These results show that perceptual organization in the auditory modality can have an effect on perceptibility in the visual modality.     

Measuring human aversion to sound without verbal descriptors

High school students tapped rapidly on a telegraph key to reduce the intensity of a continuous acoustic stimulus presented through earphones. Failure to respond resulted in an intensity increase of 1 dB every 4 sec. In Experiment 1, a group of 19 students responded to three pure tones (125, 1,000, and 8,000 Hz) and a white noise. The different asymptotic levels observed after 4 min were taken as a measure of equal aversion levels for the stimuli. In Experiment 2, the effect of the starting intensity level (45, 70, and 90 dB SPL) was determined for a 1,000-Hz tone. Differences in the asymptotic intensity levels observed after 6 rain were not significant. In Experiment 3, no significant effect was found upon varying the number of responses required to produce a 1-dB intensity decrement in a 1,000-Hz tone. Together, the experiments demonstrated the feasibility of determining equal-aversion levels for sounds.     

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.     

An examination of attentional control in the auditory modality: Further evidence for auditory orienting

Four experiments are reported that examine attentional control in the auditory modality. In Experiment 1, the subjects made detection responses to the onset of a monaurally presented pure tone that was preceded by a pure-tone cue. On a valid trial, the cue was presented in the same ear as the target; on an invalid trial, it was presented in the contralateral ear to the target; and on a neutral trial, it was presented in both ears. Overall performance was facilitated on valid trials in comparison with invalid trials. In later experiments, the subjects made choice decisions about the location of the target, and significant cuing effects were found relative to the neutral condition. Finally, performance was assessed in the presence of central (spoken) word cues. Here, the content of the cue specified the likely location of the target. Under these conditions, costs and benefits were found over a range of cue-target stimulus onset asynchronies. The results are discussed in terms of automatic and controlled attentional processes.     

Effects of stimulus ear presentation on the voice reaction time of adult stutterers and nonstutterers

The initial and optimum voice reaction times (VRT) to auditory stimuli presented separately to the left and right ears of ten adult stutterers and ten nonstutterers was investigated. Subjects initiated the neutral vowel sound /Λ/ in response to one hundred 4000 Hz tones of 2.5 sec in duration. The silent intervals between the tones varied randomly. The stimulus cues were divided into five equal response sets of 20 tones each with 10 tones in each set being presented to the right ear and 10 tones to the left ear alternating back and forth. No significant differences were reported between the VRTs for cues presented to the left or right ears for either group. However, the stutterers exhibited voice reaction times which were significantly longer and more variable than those of the nonstutterers. The between- group differences were observed for what appeared to be the “optimum” level of voice initiation for the experimental task. These results lend to the speculative hypothesis that the observed difficulty for adult stutterers to promptly and consistently initiate vocalization may in part be attributable to inherent rather than learned factors.