Altering the rhythm of target and background talkers differentially affects speech understanding

Three experiments investigated listeners’ ability to use speech rhythm to attend selectively to a single target talker presented in multi-talker babble (Experiments 1 and 2) and in speech-shaped noise (Experiment 3). Participants listened to spoken sentences of the form “Ready [Call sign] go to [Color] [Number] now” and reported the Color and Number spoken by a target talker (cued by the Call sign “Baron”). Experiment 1 altered the natural rhythm of the target talker and background talkers for two-talker and six-talker backgrounds. Experiment 2 considered parametric rhythm alterations over a wider range, altering the rhythm of either the target or the background talkers. Experiments 1 and 2 revealed that altering the rhythm of the target talker, while keeping the rhythm of the background intact, reduced listeners’ ability to report the Color and Number spoken by the target talker. Conversely, altering the rhythm of the background talkers, while keeping the target rhythm intact, improved listeners ability to report the Color and Number spoken by the target talker. Experiment 3, which embedded the target talker in speech-shaped noise rather than multi-talker babble, similarly reduced recognition of the target sentence with increased alteration of the target rhythm. This pattern of results favors a dynamic-attending theory-based selective-entrainment hypothesis over a disparity-based segregation hypothesis and an increased salience hypothesis.

     

The perceptual segregation of simultaneous auditory signals: pulse train segregation and vowel segregation

In the experiments reported here, we attempted to find out more about how the auditory system is able to separate two simultaneous harmonic sounds. Previous research (Halikia & Bregman, 1984a, 1984b; Scheffers, 1983a) had indicated that a difference in fundamental frequency (F0) between two simultaneous vowel sounds improves their separate identification. In the present experiments, we looked at the effect of F0s that changed as a function of time. In Experiment 1, pairs of unfiltered or filtered pulse trains were used. Some were steady-state, and others had gliding F0s; different F0 separations were also used. The subjects had to indicate whether they had heard one or two sounds. The results showed that increased F0 differences and gliding F0s facilitated the perceptual separation of simultaneous sounds. In Experiments 2 and 3, simultaneous synthesized vowels were used on frequency contours that were steady-state, gliding in parallel (parallel glides), or gliding in opposite directions (crossing glides). The results showed that crossing glides led to significantly better vowel identification than did steady-state F0s. Also, in certain cases, crossing glides were more effective than parallel glides. The superior effect of the crossing glides could be due to the common frequency modulation of the harmonics within each component of the vowel pair and the consequent decorrelation of the harmonics between the two simultaneous vowels.     

The effects of cognitive activity and perceptual details on speech source monitoring

Our purpose in this study was to investigate the effects of cognitive operations and perceptual details on speech source monitoring. In Phase 1, correctly spelled words and anagrams were presented in Expt 1. Words were read aloud by participants, by a same‐sex voice, or by an opposite‐sex voice. Immediately after Phase 1, in Phase 2, participants were asked whether each word had been read aloud by the participants themselves, by a same‐sex voice, or by an opposite‐sex voice. Source discrimination between own speech and that produced by a same‐sex voice was poorer than between own speech and an opposite‐sex voice. In addition, misattribution of the speech of another to one's self increased as the level of cognitive effort required for the task increased. In Expt 2, misattributions to same‐sex voice were assigned ‘know’ responses more frequently and misattributions to one's self were assigned ‘remember’ responses more frequently. These results suggest that qualitative characteristics such as perceptual detail and cognitive operations are differentially influencing misattributions to the self and those to same‐sex voices.     

Neural dynamics of perceptual order and context effects for variable-rate speech syllables

How does the brain extract invariant properties of variable-rate speech? A neural model, called PHONET, is developed to explain aspects of this process and, along the way, data about perceptual context effects. For example, in consonant-vowel (CV) syllables, such as /ba/ and /wa/, an increase in the duration of the vowel can cause a switch in the percept of the preceding consonant from /w/ to /b/ (J.L. Miller & Liberman, 1979). The frequency extent of the initial formant transitions of fixed duration also influences the percept (Schwab, Sawusch, & Nusbaum, 1981). PHONET quantitatively simulates over 98% of the variance in these data, using a single set of parameters. The model also qualitatively explains many data about other perceptual context effects. In the model, C and V inputs are filtered by parallel auditory streams that respond preferentially to the transient and sustained properties of the acoustic signal before being stored in parallel working memories. A lateral inhibitory network of onset- and rate-sensitive cells in the transient channel extracts measures of frequency transition rate and extent. Greater activation of the transient stream can increase the processing rate in the sustained stream via a cross-stream automatic gain control interaction. The stored activities across these gain-controlled working memories provide a basis for rate-invariant perception, since the transient-to-sustained gain control tends to preserve the relative activities across the transient and sustained working memories as speech rate changes. Comparisons with alternative models tested suggest that the fit cannot be attributed to the simplicity of the data. Brain analogues of model cell types are described.     

Accuracy of perceptual and acoustic methods for the detection of inspiratory loci in spontaneous speech

The present study investigates the accuracy of perceptually and acoustically determined inspiratory loci in spontaneous speech for the purpose of identifying breath groups. Sixteen participants were asked to talk about simple topics in daily life at a comfortable speaking rate and loudness while connected to a pneumotach and audio microphone. The locations of inspiratory loci were determined on the basis of the aerodynamic signal, which served as a reference for loci identified perceptually and acoustically. Signal detection theory was used to evaluate the accuracy of the methods. The results showed that the greatest accuracy in pause detection was achieved (1) perceptually, on the basis of agreement between at least two of three judges, and (2) acoustically, using a pause duration threshold of 300 ms. In general, the perceptually based method was more accurate than was the acoustically based method. Inconsistencies among perceptually determined, acoustically determined, and aerodynamically determined inspiratory loci for spontaneous speech should be weighed in selecting a method of breath group determination.     

The unilateral field advantage in repetition detection: Effects of perceptual grouping and task demands

This study examines interhemispheric interactions in detecting objects that are simultaneously repeated in an array of objects. Previous studies have shown that presenting two identical objects to a single hemifield speeds up repetition detection. This unilateral field advantage (UFA) is often attributed to the relatively low-level processing demands for detecting a perceptual repetition, and more specifically, to more efficient perceptual grouping processes within a hemisphere than between hemispheres. To directly examine the impact of perceptual grouping and task demands on interhemispheric interactions, we asked participants to judge whether four items, one presented in each visual quadrant, were all different, or whether any two were the same, along an instructed dimension. We found that in comparison with the UFA for identical objects, the UFA for repetition detection in accuracy was similar or greater when the matching objects were not perceptually identical and differed in color, size, or viewpoint. Thus, decreasing grouping strength and increasing computational complexity did not reduce the UFA. Results are interpreted in terms of the callosal degradation account of the UFA.     

Processing linguistic and perceptual dimensions of speech: interactions in speeded classification.

Performance on selective-attention and divided-attention tasks shows strong and consistent interactions when participants rapidly classify auditory stimuli whose linguistic and perceptual dimensions (the words low vs. high, low and high pitch, low and high position in space) share common labels. Compared with baseline performance, response times were greater when one or two irrelevant dimensions varied (Garner interference) and when combinations of attributes were incongruent rather than congruent (congruence effects). Performance depended only on the congruence relationships between the relevant dimension and each of the irrelevant dimensions and not on the congruence relationships between the irrelevant dimensions themselves. In selective attention, an additive multidimensional model accounts well for the patterns of both Garner interference and congruence effects.     

The development of cognitive inhibition in streams-of-consciousness and directed speech

This research examined the development of the ability to inhibit thoughts within free speech by manipulating the content requirements of overt streams-of-consciousness. A picture-naming task with procedural manipulations similar to the stream-of-consciousness task was created as an additional method of investigating the development of the inhibition of speech. Comparison of adults' performance in the two tasks indicated that mature performance reflected inhibitory processing rather than selective attention. The children's performance in the stream-of-consciousness task suggested a developmental change in their ability to produce a stream-of-consciousness overtly. An investigation of inhibition in the picture-naming task with kindergartners, second graders, fifth graders and adults revealed a developmental improvement in inhibitory ability over the middle childhood years. These results are consistent with the interpretation that developmental improvements in cognitive inhibition contribute to developmental improvements in cognitive function on a variety of tasks.     

Examination of perceptual reorganization for nonnative speech contrasts: Zulu click discrimination by English-speaking adults and infants

The language environment modifies the speech perception abilities found in early development. In particular, adults have difficulty perceiving many nonnative contrasts that young infants discriminate. The underlying perceptual reorganization apparently occurs by 10-12 months. According to one view, it depends on experiential effects on psychoacoustic mechanisms. Alternatively, phonological development has been held responsible, with perception influenced by whether the nonnative sounds occur allophonically in the native language. We hypothesized that a phonemic process appears around 10-12 months that assimilates speech sounds to native categories whenever possible; otherwise, they are perceived in auditory or phonetic (articulatory) terms. We tested this with English-speaking listeners by using Zulu click contrasts. Adults discriminated the click contrasts; performance on the most difficult (80% correct) was not diminished even when the most obvious acoustic difference was eliminated. Infants showed good discrimination of the acoustically modified contrast even by 12-14 months. Together with earlier reports of developmental change in perception of nonnative contrasts, these findings support a phonological explanation of language-specific reorganization in speech perception.     

Strategic hand use preferences and hemispheric specialization in tactual reading: impact of the demands of perceptual encoding

Four reading-related, information-processing tasks were administered to right-handed blind readers of braille who differed in level of reading skill and in preference for using the right hand or the left hand when required to read text with just one hand. The tasks were letter identification, same-different matching of letters that differed in tactual similarity, short-term memory for lists of words that varied in tactual and phonological similarity, and paragraph reading with and without a concurrent memory load of digits. The results showed interactions between hand preference and the hand that was actually used to read the stimulus materials, such that left preferrers were significantly faster and more accurate with their left hands than with their right hands whereas right preferrers were slightly but usually not significantly faster with their right hands than with their left hands. In all cases, the absolute magnitude of the left-hand advantage among left preferrers was substantially larger than the right-hand advantage among right preferrers. The results suggest that encoding strategies for dealing with braille are reflected in hand preference and that such strategies operate to modify an underlying but somewhat plastic superiority of the right hemisphere for dealing with the perceptual requirements of tactual reading. These requirements are not the same as those of visual reading, leading to some differences in patterns of hemispheric specialization between readers of braille and readers of print.     

Authenticity affects the recognition of emotions in speech: behavioral and fMRI evidence

The aim of the present study was to determine how authenticity of emotion expression in speech modulates activity in the neuronal substrates involved in emotion recognition. Within an fMRI paradigm, participants judged either the authenticity (authentic or play acted) or emotional content (anger, fear, joy, or sadness) of recordings of spontaneous emotions and reenactments by professional actors. When contrasting between task types, active judgment of authenticity, more than active judgment of emotion, indicated potential involvement of the theory of mind (ToM) network (medial prefrontal cortex, temporoparietal cortex, retrosplenium) as well as areas involved in working memory and decision making (BA 47). Subsequently, trials with authentic recordings were contrasted with those of reenactments to determine the modulatory effects of authenticity. Authentic recordings were found to enhance activity in part of the ToM network (medial prefrontal cortex). This effect of authenticity suggests that individuals integrate recollections of their own experiences more for judgments involving authentic stimuli than for those involving play-acted stimuli. The behavioral and functional results show that authenticity of emotional prosody is an important property influencing human responses to such stimuli, with implications for studies using play-acted emotions.     

The role of perceptual and cognitive processes in addition-subtraction studies with 5-month-old infants

After a brief familiarization period to either one or two toys 5-month-olds gave a clear preference for perceptually novel displays, suggesting that replicable findings of greater looking at an unexpected arithmetic outcome in addition/subtraction experiments cannot easily be attributed to simple familiarity preferences.     

Looking back with regret: Visual perspective in memory images differentially affects regret for actions and inactions

People can regret things they've done and things they've failed to do. However, the experience of a regrettable action tends to be painful, while regrettable inactions tend to be painful only when one considers the inaction's impact in the broader context of one's life as a whole (Gilovich & Medvec, 1995). Three experiments manipulated the visual perspective (own first-person vs. observer's third-person) that participants used to picture regretted actions or inactions from their lives. Imagery perspective influences the degree to which people's understanding of events is determined by features of the event itself (first-person) or by the integration of the event with broader self-knowledge (third-person) (Libby & Eibach, in press-b). As predicted, relative to first-person imagery, third-person imagery reduced regret for actions but increased regret for inactions. Results provide new insight into the relationship between imagery perspective, meaning-making, and emotion, and suggest ways to strategically increase or decrease regret.     

Differences in the cognitive demands of word order,plural, and subject-verb agreement constructions

The syntactic devices of subject-verb-object word order, regular plurals, and subject-verb agreement differ in age of acquisition and susceptibility to error within language-disordered populations. In the present article, the performance of adults on a grammaticality judgment task is used to explore whether such differences are related to working memory (both in terms of an externally imposed load and individual differences in capacity) and phonological ability. The results show that word order, the earliest acquired and most resilient device, is not affected by load, memory span, or phonological ability. Plurals are affected marginally by load and significantly by phonological ability. Agreement, the last acquired and least resilient device, is affected by load, memory span, and phonological ability. Thus, consistent with a processing-based explanation, later acquired and less resilient devices have higher working memory and phonological demands.