Perceptual restoration in toddlers

Perception by adults is a constant interaction between the top-down effects of prior knowledge and the effects of bottom-up perceptual information. One obvious example of this interaction is the perceptual restoration effect, in which adult listeners have the illusion that a word is complete when a portion of it has been replaced by a masking noise. In four experiments, we demonstrate that toddlers fail to show the illusion of perceptual restoration, even in constrained situations with words they know quite well. Not only do toddlers have less prior knowledge than do adults, but they also appear to place less reliance on the knowledge that they do have, at least in the paradigm tested here. Instead, toddlers appear to be more tied to the perceptual information they receive than are adults.     

Perceptual restoration of a "missing" speech sound: auditory induction or illusion?

This study investigated whether the apparent completeness of the acoustic speech signal during phonemic restoration derives from a process of auditory induction (Warren, 1984) or segregation, or whether it is an auditory illusion that accompanies the completion of an abstract phonological representation. Specifically, five experiments tested the prediction of the auditory induction (segregation) hypothesis that active perceptual restoration of an [s] noise that has been replaced with an extraneous noise would use up a portion of that noise's high-frequency energy and consequently change the perceived pitch (timbre, brightness) of the extraneous noise. Listeners were required to compare the pitch of a target noise, which replaced a fricative noise in a sentence, with that of a probe noise preceding or following the speech. In the first two experiments, a significant tendency was found in favor of the auditory induction hypothesis, although the effect was small and may have been caused by variations in acoustic context. In the following three experiments, a larger variety of stimuli were used and context was controlled more carefully; this yielded negative results. Phoneme identification responses collected in the same experiments, as well as informal observations about the quality of the restored phoneme, suggested that restoration of a fricative phone distinct from the extraneous noise did not occur; rather, the spectrum of the extraneous noise itself influenced phoneme identification. These results suggest that the apparent auditory restoration which accompanies phonemic restoration is illusory, and that the schema-guided process of phoneme restoration does not interact with auditory processing.     

Perceptual restoration of a “missing” speech sound: Auditory induction or illusion?

This study investigated whether the apparent completeness of the acoustic speech signal during phonemic restoration derives from a process of auditory induction (Warren, 1984) or segregation, or whether it is an auditory illusion that accompanies the completion of an abstract phonological representation. Specifically, five experiments tested the prediction of the auditory induction (segregation) hypothesis that active perceptual restoration of an [s] noise that has been replaced with an extraneous noise would use up a portion of that noise’s high-frequency energy and consequently change the perceived pitch (timbre, brightness) of the extraneous noise. Listeners were required to compare the pitch of a target noise, which replaced a fricative noise in a sentence, with that of a probe noise preceding or following the speech. In the first two experiments, a significant tendency was found in favor of the auditory induction hypothesis, although the effect was small and may have been caused by variations in acoustic context. In the following three experiments, a larger variety of stimuli were used and context was controlled more carefully; this yielded negative results. Phoneme identification responses collected in the same experiments, as well as informal observations about the quality of the restored phoneme, suggested that restoration of a fricative phone distinct from the extraneous noise did not occur; rather, the spectrum of the extraneous noise itself influenced phoneme identification. These results suggest that the apparent auditory restoration which accompanies phonemic restoration is illusory, and that the schema-guided process of phoneme restoration does not interact with auditory processing.     

Increasing the intelligibility of speech through multiple phonemic restorations.

Outside of the laboratory, listening conditions are often less than ideal, and when attending to sounds from a particular source, portions are often obliterated by extraneous noises. However, listeners possess rather elegant reconstructive mechanisms. Restoration can be complete, so that missing segments are indistinguishable from those actually present and the listener is unaware that the signal is fragmented. This phenomenon, called temporal induction (TI), has been studied extensively with nonverbal signals and to a lesser extent with speech. Earlier studies have demonstrated that TI can produce illusory continuity spanning gaps of a few hundred milliseconds when portions of a signal are replaced by a louder sound capable of masking the signal were it actually present. The present study employed various types of speech signals with periodic gaps and measured the effects upon intelligibility produced by filling these gaps with noises. Enhancement of intelligibility through multiple phonemic restoration occurred when the acoustic requirements for TI were met and when sufficient contextual information was available in the remaining speech fragments. It appears that phonemic restoration is a specialized form of TI that uses linguistic skills for the reconstruction of obliterated speech.     

Increasing the intelligibility of speech through multiple phonemic restorations

Outside of the laboratory, listening conditions are often less than ideal, and when attending to sounds from a particular source, portions are often obliterated by extraneous noises. However, listeners possess rather elegant reconstructive mechanisms. Restoration can be complete, so that missing segments are indistinguishable from those actually present and the listener is unaware that the signal is fragmented. This phenomenon, called temporal induction (TI), has been studied extensively with nonverbal signals and to a lesser extent with speech. Earlier studies have demonstrated that TI can produce illusory continuity spanning gaps of a few hundred milliseconds when portions of a signal are replaced by a louder sound capable of masking the signal were it actually present. The present study employed various types of speech signals with periodic gaps and measured the effects upon intelligibility produced by filling these gaps with noises. Enhancement of intelligibility through multiple phonemic restoration occurred when the acoustic requirements for TI were met and when sufficient contextual information was available in the remaining speech fragments. It appears that phonemic restoration is a specialized form of TI that uses linguistic skills for the reconstruction of obliterated speech.     

Shrinkage in the perceived duration of speech and tone by acoustic replacement1

Abstract: To investigate mechanisms for perceiving the duration of an auditory event, an effect of perceptual grouping upon perceived duration was studied psychophysically. In the first experiment, the perceived duration of a spoken word was measured under three conditions of acoustic continuity (i.e., (a) intact, (b) noise‐replaced, and (c) gap‐replaced) as a function of the duration of the target stimulus. Under the noise‐replaced condition, a portion of the target stimulus was physically replaced with a noise burst. Under the gap‐replaced condition, the replacement was made with a gap. The gap‐replacement resulted in a prominent shrinkage of the perceived duration. In the case of noise‐replacement, the amount of shrinkage was moderate but highly significant, although the word employed was perceived to be phonetically intact. Independent of this effect of replacement, the amount of shrinkage was also affected by the physical duration of the target stimulus. The second experiment tested an effect of noise replacement on the perceived duration of a tone burst. In this case, the noise replacement also shrunk the perceived duration of the non‐speech stimulus. This noise‐induced shrinkage could be regarded as being general for the auditory duration. The phenomenon is discussed in relation to a revised model for perceived duration.     

Phonemic restorations based on subsequent context

Earlier experiments have shown that when one or more speech sounds in a sentence are replaced by a noise meeting certain criteria, the listener mislocalizes the extraneous sound and believes he hears the missing phoneme(s) clearly. The present study confirms and extends these earlier reports of phonemic restorations under a variety of novel conditions. All stimuli had some of the context necessary for the appropriate phonemic restoration following the missing sound, and all sentences had the missing phoneme deliberately mispronounced before electronic deletion (so that the neighboring phonemes could not provide acoustic cues to aid phonemic restorations). The results are interpreted in terms of mechanisms normally aiding veridical perception of speech and nonspeech sounds.     

The auditory continuity illusion: a parametric investigation and filter model

A sound that is briefly interrupted by a silent gap is perceived as discontinuous. However, when the gap is filled with noise, the sound may be perceived as continuing through the noise. It has been shown that this continuity illusion depends on the masking of the omitted target sound, but the underlying mechanisms have yet to be quantified thoroughly. In this article, we systematically quantify the relation between perceived continuity and the duration, relative power, or notch width of the interrupting broadband noise for interrupted and noninterrupted amplitude-modulated tones at different frequencies. We fitted the psychometric results in order to estimate the range of the noise parameters that induced auditory grouping. To explain our results within a common theoretical framework, we applied a power spectrum model to thedifferent masking resultsand estimated the critical bandwidth of the auditory filter that may be responsible for the continuity illusion. Our results set constraints on the spectral resolution of the mechanisms underlying the continuity illusion and provide a stimulus set that can be readily applied for neurophysiological studies of its neural correlates.     

The haptic Müller-Lyer illusion in sighted and blind people

We examined the effect of visual experience on the haptic Müller-Lyer illusion. Subjects made size estimates of raised lines by using a sliding haptic ruler. Independent groups of blind-folded-sighted, late-blind, congenitally blind, and low-vision subjects judged the sizes of wings-in and wings-out stimuli, plain lines, and lines with short vertical ends. An illusion was found, since the wings-in stimuli were judged as shorter than the wings-out patterns and all of the other stimuli. Subjects generally underestimated the lengths of lines. In a second experiment we found a nonsignificant difference between length judgments of raised lines as opposed to smooth wooden dowels. The strength of the haptic illusion depends upon the angles of the wings, with a much stronger illusion for more acute angles. The effect of visual status was nonsignificant, suggesting that spatial distortion in the haptic Müller-Lyer illusion does not depend upon visual imagery or visual experience.     

When less is heard than meets the ear: change deafness in a telephone conversation

During a conversation, we hear the sound of the talker as well as the intended message. Traditional models of speech perception posit that acoustic details of a talker's voice are not encoded with the message whereas more recent models propose that talker identity is automatically encoded. When shadowing speech, listeners often fail to detect a change in talker identity. The present study was designed to investigate whether talker changes would be detected when listeners are actively engaged in a normal conversation, and visual information about the speaker is absent. Participants were called on the phone, and during the conversation the experimenter was surreptitiously replaced by another talker. Participants rarely noticed the change. However, when explicitly monitoring for a change, detection increased. Voice memory tests suggested that participants remembered only coarse information about both voices, rather than fine details. This suggests that although listeners are capable of change detection, voice information is not continuously monitored at a fine-grain level of acoustic representation during natural conversation and is not automatically encoded. Conversational expectations may shape the way we direct attention to voice characteristics and perceive differences in voice.     

Can you tickle yourself if you swap bodies with someone else?

The effect of the body transfer illusion on the perceived strength of self- and externally-generated “tickle” sensations was investigated. As expected, externally generated movement produced significantly higher ratings of tickliness than those associated with self-generated movements. Surprisingly, the body transfer illusion had no influence on the ratings of tickliness, suggesting that highly surprising, and therefore hard to predict, experiences of body image and first-person perspective do not abolish the attenuation of tickle sensations. In addition, evidence was found that a version of the rubber hand illusion exists within the body transfer illusion. We situate our findings within the larger debate over sensory attenuation: (1) there is an attenuation of prediction errors that depends upon the context in which sensory input is predicted (i.e., efference copy), and (2) sensory attenuation is a necessary consequence of self-generated movement irrespective of context (i.e., active inference). The results support the notion of active inference.     

Judgmental illusion produced by contrast with expectancy

Judgments of the numerousness of dots vary inversely with the size of the background on which the dots are presented. An expectancy-contrast model is proposed and tested in an experiment with this size-numerosity illusion. According to the model, the expectancy for numerousness depends upon the subjective correlation between size and numerosity; judgments-of numerousness are assumed to reflect an additive contrast with the expectancy. In agreement with the model, the data demonstrate that the effects of size depend upon the correlation between size and numerosity; when this correlation is negative, the illusion is reversed. The model received tentative support from quantitative tests of fit, based on functional measurement procedures.     

Attention within auditory word perception: insights from the phonemic restoration illusion

Phonemic restoration is a powerful auditory illusion that arises when a phoneme is removed from a word and replaced with noise, resulting in a percept that sounds like the intact word with a spurious bit of noise. It is hypothesized that the configurational properties of the word impair attention to the individual phonemes and thereby induce perceptual restoration of the missing phoneme. If so, this impairment might be unlearned if listeners can process individual phonemes within a word selectively. Subjects received training with the potentially restorable stimuli (972 trials with feedback); in addition, the presence or absence of an attentional cue, contained in a visual prime preceding each trial, was varied between groups of subjects. Cuing the identity and location of the critical phoneme of each test word allowed subjects to attend to the critical phoneme, thereby inhibiting the illusion, but only when the prime also identified the test word itself. When the prime provided only the identity or location of the critical phoneme, or only the identity of the word, subjects performed identically to those subjects for whom the prime contained no information at all about the test word. Furthermore, training did not produce any generalized learning about the types of stimuli used. A limited interactive model of auditory word perception is discussed in which attention operates through the lexical level.     

Dependence of illusory motion on directional consistency in oblique components

Pinna and Brelstaff (2000 Vision Research 40 2091-2096) reported a motion illusion on viewing two concentric circles consisting of quadrangular components with black and white sides on a grey background. Our results suggest that the illusion is based on the integration of motion signals derived from oblique components, and on the consistency in the direction among those components. Furthermore, arrays of these oblique components can elicit the perception of motion not only for the oblique components themselves, but also for other objects in the picture. We propose that the motion illusion depends not only upon detection of the illusory motion signal at each local oblique component, but also upon the accumulation of the signal all over the stimulus configuration.     

Infants' perception of illusions in sound localization: reaching to sounds in the dark.

Sixteen infants each at 4, 6, and 8 months of age were tested for reaching to sounding toys in the dark under two auditory illusion conditions: the Haas-effect, which creates the illusion of a single lateralized sound based on an interaural intensity difference (the toy was visible and invisible under some test conditions); and the midline illusion, which creates the illusion of a single sound at midline due to an absence of any interaural time or intensity differences (invisible toy condition only). No-sound control trials indicated the level of spontaneous reaching in the dark. Results indicate that by 4 months infants perceive both the Haas-effect and midline illusions. The ability to reach both for invisible and visible sounding objects in the dark was well developed by 4 months of age, although developmental changes in aspects of reaching behavior were observed and, at all ages, object contact was most frequent when visual localization cues accompanied sound localization cues. The incidence of spontaneous reaching in the dark was low and did not vary with age. Theoretical and methodological implications of this research are discussed.     

The effect of vowel similarity and syllable length on acoustic memory

Darwin and Baddeley (1974) argue that the presence of recency, suffix, and modality effects are not attributable to the acoustic properties of the stimuli but, rather, to the acoustic distance between the items comprising the test series. The present study is designed to determine whether stimulus duration is a significant variable in acoustic memory. Eight different blocks of synthetic stimuli were prepared; one block each of 60 msec similar and dissimilar syllables and 190 msec similar and dissimilar syllables. The other four blocks consisted of these same vocabularies, but each list in the block had an eighth syllable suffix of the same duration as the syllables in the block. Significant recency and suffix effects are seen for dissimilar syllables of both durations. No effects are demonstrated for 60-msec similar syllables, but both of the effects are seen for 190-msec similar syllables. These results indicate that whether or not a speech sound is preserved in precategorical acoustic storage (PAS) depends upon not only the acoustic distance between the stimuli, but also on other characteristics intrinsic to the stimuli, e.g., stimulus duration.     

Central visual learning and illusory visual direction after backward head tilts

When the head is returned to upright after prolonged backward tilt, people who are asked to look straight ahead look higher than they did before the backward tilting. This has been interpreted in terms of hypotheses about central visual learning or by hypotheses about peripheral muscle physiology. According to the learning hypotheses, the illusion of visual direction that occurs after head tilts depends upon the presence of discordant cues about direction. In the present study, the illusion was the same with or without discordant information.     

The effect of spectral difference on auditory saltation

Auditory saltation is a spatiotemporal illusion in which the judged positions of sound stimuli are shifted toward subsequent stimuli that follow closely in time and space. In this study, the "reduced-rabbit" paradigm and a direct-location method were employed to investigate the effect of spectral sound content on the saltation illusion. Eighteen listeners were presented with sound sequences consisting of three high-pass or low-pass filtered noise bursts. Noise bursts within a sequence were either the same or differed in frequency. Listeners judged the position of the second sound using a hand pointer. When the time interval between the second and third sound was short, the target was shifted toward the location of the subsequent stimulus. This displacement effect did not depend on the spectral content of the first sound, but decreased substantially when the second and third sounds were different. The results indicated an effect of spectral difference on saltation that is discussed with regard to a recently proposed stimulus integration approach in which saltation was attributed to an interaction between perceptual processing of temporally proximate stimuli.     

The discrepancy-attribution hypothesis: II. Expectation, uncertainty, surprise, and feelings of familiarity

In the accompanying article (B. W. A. Whittlesea & L. D. Williams, 2001), surprising violation of an expectation was observed to cause an illusion of familiarity. The authors interpreted that evidence as support for the discrepancy-attribution hypothesis. This article extended the scope of that hypothesis, investigating the consequences of surprising validation of expectations. Subjects were shown recognition probes as completions of sentence stems. Their expectations were manipulated by presenting predictive, nonpredictive, and inconsistent stems. Predictive stems caused an illusion of familiarity, but only when the subjects also experienced uncertainty about the outcome. That is, as predicted by the discrepancy-attribution hypothesis, feelings of familiarity occurred only when processing of a recognition target caused surprise. The article provides a discussion of the ways in which a perception of discrepancy can come about, as well as the origin and nature of unconscious expectations.