Reaction times to comparisons within and across phonetic categories

Same-different reaction times (RTs) were obtained to pairs of synthetic speech sounds ranging perceptually from /ba/ through /pa/. Listeners responded “same” if both stimuli in a pair were the same phonetic segments (i.e., /ba/-/ba/ or /pa/-/pa/) or “different” if both stimuli were different phonetic segments (i.e., /ba/-/pa/ or /pa/-/ba/). RT for “same” responses was faster to pairs of acoustically identical stimuli (A-A) than to pairs of acoustically different stimuli (A-a) belonging to the same phonetic category. RT for “different” responses was faster for large acoustic differences across a phonetic boundary than for smaller acoustic differences across a phonetic boundary. The results suggest that acoustic information for stop consonants is available to listeners, although the retrieval of this information in discrimination will depend on the level of processing accessed by the particular information processing task.     

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.     

Duration discrimination of empty and filled intervals marked by auditory and visual signals

Experiments 1 and 2 compared, with a single-stimulus procedure, the discrimination of filled and empty intervals in both auditory and visual modalities. In Experiment 1, in which intervals were about 250 msec, the discrimination was superior with empty intervals in both modalities. In Experiment 2, with intervals lasting about 50 msec, empty intervals showed superior performance with visual signals only. In Experiment 3, for the auditory modality at 250 msec, the discrimination was easier with empty intervals than with filled intervals with both the forced-choice (FC) and the single stimulus (SS) modes of presentation, and the discrimination was easier with the FC than with the SS method. Experiment 4, however, showed that at 50 and 250 msec, with a FC-adaptive procedure, there were no differences between filled and empty intervals in the auditory mode; the differences observed with the visual mode in Experiments 1 and 2 remained significant. Finally, Experiment 5 compared differential thresholds for four marker-type conditions, filled and empty intervals in the auditory and visual modes, for durations ranging from .125 to 4 sec. The results showed (1) that the differential threshold differences among marker types are important for short durations but decrease with longer durations, and (2) that a generalized Weber’s law generally holds for these conditions. The results as a whole are discussed in terms of timing mechanisms.     

Spare the rod and spoil the icon

Short-term visual storage was investigated with a successive field paradigm, so that correct performance depended upon combining visual information from two targets that were never on simultaneously. In the first two experiments, the stimuli consisted of two slides, each containing a 10' red dot on a gray surround, and separated by an interstimulus interval (ISI) from 20 to 400 msec. Subjects had to determine if the dots were vertically or horizontally aligned. In Experiment 1, the stimuli had either no contrast for the rods or no luminance contrast for the cones or high contrast. At short ISIs the cone contrast determined performance, whereas at long ISIs the rod contrast determined performance. In fact, when the dots were invisible to the rods, the task was impossible for long ISIs. In Experiment 2, performance was compared for zero log rod contrast and for small departures from zero. Even a small departure from zero log rod contrast resulted in above-chance performance. In Experiment 3, the stimuli were luminous rectangles and the task was to decide whether or not a 4' spatial gap was present between the two successively presented rectangles. Wavelength, luminance, and ISI were varied under both photopic and scotopic adapting conditions. The result was that the rods performed the task for ISIs of 150 msec or longer under scotopic conditions and under the photopic conditions that we were able to test. The results of the experiments taken together are consistent with the hypothesis that the cone icon is short, whereas the rod icon is robust and long lasting.     

The role of duration and rapid temporal processing on the lateral perception of consonants and vowels

This study explored the extent to which rapid temporal processing and duration contribute to the right-ear advantage (REA) and presumably left-hemisphere processing for stop consonants and the lack of clear-cut laterality effects for vowels. Three sets of synthetic stimuli were constructed: consonant vowel stimuli [ba da ga bi di gi bu du gu] of 300 msec duration (full stimuli) and two shortened stimuli consisting either of a noise burst and 40-msec transitions (40-msec stimuli), or a noise burst and 20-msec transitions (20-msec stimuli). Stimuli were presented dichotically for consonant, vowel, and syllable identification. Results indicated a significant REA for consonants in the full and 40-msec conditions and a non-significant REA in the 20-msec condition. Nevertheless, the magnitude of laterality did not change across the three conditions. These results suggest that although transition information including duration contributes to lateralization for stop consonants, it is the presence of abrupt onsets which crucially determines lateralized processing. For vowels, there was a significant REA only in the full stimulus condition, and a significant decrement in the magnitude of the laterality effect in the two shortened stimulus conditions. These results suggest that for vowel perception, it is the nature of the acoustic cue used for phonetic identification and not duration that seems to be the critical determinant of lateralization effects.     

VOT discrimination by four to six and a half month old infants from Spanish environments.

Thirty 4–6.5 mo-old-infants from monolingual Spanish speaking homes were tested for discrimination of bilabial stop consonants differing in VOT. Discrimination was determined by the habituation and dishabituation of the orienting reflex as indexed by cardiac deceleration. Subjects were placed in one of three groups of ten subjects each. The three groups were used to determine whether bilabial stops with VOT values of ?60 and ?20 msec, ?20 and +20 msec or +20 and +60 msec could be discriminated. Subjects were presented eight trial blocks of ten repetitions of a CV syllable; these eight trial blocks were followed by two trial blocks of ten repetitions of a different CV syllable. The only difference between the CV syllables presented during the first eight and the last two trial blocks was the VOT value of the bilabial stop consonants. Subjects in the ?20 and +20 msec group showed no signs of being able to discriminate these stimuli while the subjects in the ?60 and ?20 msec group and the +20 and +60 msec group did. These results correspond to those reported for infants from English speaking families but do not correspond to those reported for Spanish speaking adults. Thus, the failure to find evidence of discrimination in the ?20 and +20 msec group suggests that experience has little effect in determining bilabial stop phonetic categories in 4–6.5 mo-old infants.     

Reaction time to the second of two shortly spaced auditory signals both varying in intensity

Six subjects participated in a reaction time (RT) task in which the stimulus events consisted of two sinusoidal waves presented in close succession. The leading stimulus (S₁) had a duration of 25 msec while the binary reaction stimulus (S₂) was 250 msec. Presentation of the interstimulus interval (ISI) was irregular. S₁ as well as S₂ varied in intensity and were assigned randomly the values of 45, 68, 85 and 105 db (SPL). RT to S₂ was examined as a function of the intensity of both stimuli. Generally RT varied inversely with the intensity of S₁ and the downward gradient of RT with ISI became steepened at least for ISIs shorter than 200–250 msec. Concerning S₂, RT grew shorter as the intensity increased up to 85 db. Probably due to startle, RT tended to lengthen at S₂ = 105 db. When both S₁ and S₂ were 105 db the startle effect upon RT seemed most evident. Then the elevation in RT took place at especially those ISIs for which he fastest RTs might have been expected (about 200 msec). For the remaining intensities no interaction between S₁ and S₂ upon RT was found even for the shortest ISIs, implying that the effects of S₁ and S₂ intensities upon RT were independent.     

Simultaneous presentation of similar stimuli produces perceptual learning in human picture processing

Human participants received unsupervised exposure to difficult-to-discriminate stimuli (e.g., A and A'), created with a morphing procedure from photographs of faces, before learning a discrimination between them. Experiments 1 and 2 demonstrated that prior exposure enhanced later discrimination and that intermixed exposure (A, A', A, A'...) resulted in better subsequent discrimination than blocked exposure (B, B, ...B', B'...). Experiments 3 and 4 showed that simultaneous exposure to 2 similar stimuli facilitated the later acquisition of both a simultaneous and a successive discrimination, and this effect was observed even though simultaneous exposure to 2 stimuli fostered the development of an excitatory association between them (Experiment 5). The findings of Experiments 1 and 2 revealed a perceptual learning effect with pictures of faces, and the findings of Experiments 3-5 are difficult to reconcile with associative analyses of perceptual learning.     

Ultra-precise quantal timing: evidence from simultaneity thresholds in long-range apparent movement.

Conditions for the disappearance of long-range apparent movement were investigated. In an experiment on beta motion, critical interstimulus intervals (ISIs) of downward simultaneity thresholds for stimuli presented in continuous alternation were determined for exposure durations (EDs) varying from 3 to 160 msec. Each subject performed each test twice. Data were collected in three sessions, each for one of three angular separations (3 degrees, 6 degrees, and 12 degrees) and the full set of EDs. The distribution of critical ISIs collapsed across subjects, EDs, and angular separations shows sharp maxima at regular distances within a range of 0-110 msec ISI. Significant or near-significant peaks were found at ISIs of 5, 9, 22, 27, 43, 55, and 107 msec. Although mean critical ISIs shifted with spatial separation, no essential shift of the main maxima occurred. Evidence of a periodic modulation with a period duration of 4.5 msec was obtained from the distributions of differences between critical ISIs of the first tests and their replications, which exhibit extremely low standard deviations (< 10 msec). These results agree well with previous analyses (Geissler, 1987, 1992) that led to a taxonomic model of quantal timing, briefly summarized in this paper. Further consequences are discussed and related to earlier developments (Geissler, 1991, 1992, 1997).     

Ultra-precise quantal timing: Evidence from simultaneity thresholds in long-range apparent movement

Conditions for the disappearance of long-range apparent movement were investigated. In an experiment on beta motion, critical interstimulus intervals (ISIs) of downward simultaneity thresholds for stimuli presented in continuous alternation were determined for exposure durations (EDs) varying from 3 to 160 msec. Each subject performed each test twice. Data were collected in three sessions, each for one of three angular separations (3°, 6°, and 12°) and the full set of EDs. The distribution of critical ISIs collapsed across subjects, EDs, and angular separations shows sharp maxima at regular distances within a range of 0–110 msec ISI. Significant or near-significant peaks were found at ISIs of 5, 9,22,27, 43, 55, and 107 msec. Although mean critical ISIs shifted with spatial separation, no essential shift of the main maxima occurred. Evidence of a periodic modulation with a period duration of 4.5 msec was obtained from the distributions of differences between critical ISIs of the first tests and their replications, which exhibit extremely low standard deviations (< 10 msec). These results agree well with previous analyses (Geissler, 1987, 1992) that led to a taxonomic model of quantal timing, briefly summarized in this paper. Further consequences are discussed and related to earlier developments (Geissler, 1991, 1992,1997).     

Cultural and linguistic factors in audiovisual speech processing: The McGurk effect in Chinese subjects

The “McGurk effect” demonstrates that visual (lip-read) information is used during speech perception even when it is discrepant with auditory information. While this has been established as a robust effect in subjects from Western cultures, our own earlier results had suggested that Japanese subjects use visual information much less than American subjects do (Sekiyama & Tohkura, 1993). The present study examined whether Chinese subjects would also show a reduced McGurk effect due to their cultural similarities with the Japanese. The subjects were 14 native speakers of Chinese living in Japan. Stimuli consisted of 10 syllables (/ba/, /pa/, /ma/, /wa/, /da/, /ta/, /na/, /ga/, /ka/, /ra/ ) pronounced by two speakers, one Japanese and one American. Each auditory syllable was dubbed onto every visual syllable within one speaker, resulting in 100 audiovisual stimuli in each language. The subjects’ main task was to report what they thought they had heard while looking at and listening to the speaker while the stimuli were being uttered. Compared with previous results obtained with American subjects, the Chinese subjects showed a weaker McGurk effect. The results also showed that the magnitude of the McGurk effect depends on the length of time the Chinese subjects had lived in Japan. Factors that foster and alter the Chinese subjects’ reliance on auditory information are discussed.     

Phonology in multisyllabic word recognition

The present study used two word-naming experiments to investigate whether a phonological representation is computed in the perception of multisyllabic words. In the first experiment, 100- or 250-msec beginning syllable previews were given, followed by the whole word. The results indicated that no phonological representation was computed at 100 msec, but a phonological representation was computed at 250 msec. In Experiment 2, the second syllable was given as a prime for either 100 or 250 msec. The results showed that no phonological representation was computed for the end of a multisyllabic word. Results are discussed in terms of current dual-route theory and connectionist models.This research was supported by a National Science Foundation grant BNS90110067. We thank Kim Clements, Cindy Connine, Fred Smith, Steve Straight, Sheldon Li, Steve Specht, Greg Boheimer, Deb Briihl, Rich Topoloski, Anna Chomiak and Chris Bruun for their support.     

Judgments of duration, figure-ground contrast, and size for words and nonwords

Does the word-superiority effect on letter discrimination result in a word-superiority effect on duration judgments? We examined this question in five experiments. In the first four experiments, we have demonstrated that (1) words shown for 32-80 msec were judged as presented longer than non-words shown for the same duration; (2) this word-superiority effect persists if the stimuli are shown for an objective duration of up to 250 msec; and (3) these effects can be extended to judgments of figure-ground contrast and letter size. These findings extend existing data on effects of processing fluency on perceptual judgments. In Experiment 5, we found that duration judgments were higher for words than for pronounceable nonwords, and duration judgments were higher for pronounceable non-words than for nonpronounceable nonwords. We discuss the implications of this finding for the discrepancy-attribution hypothesis.     

Speech perception by rhesus monkeys: The voicing distinction in synthesized labial and velar stop consonants

Monkeys were presented with synthetic speech stimuli in a shock-avoidance situation. On the basis of their behavior, perceptual boundaries were determined along the physical continua between /ba/ and /pa/, and /ga/ and /ka/, that were close to the human boundaries between voiced and voiceless consonants. As is the case with humans, discrimination across a boundary was better than discrimination between stimuli that were both on one side of the boundary, and there was generalization of the voiced-voiceless distinction from labial to velar syllables. Unlike humans, the monkeys showed large shifts in boundary when the range of stimuli was varied.     

Sensorimotor synchronization: Motor responses to pseudoregular auditory patterns

Musically trained and untrained subjects (N=30) were asked to synchronize their finger tapping with stimuli in auditory patterns. Each pattern comprised six successive tonal stimuli of the same duration, the first of which was accented by a different frequency. The duration of interstimulus onset intervals (ISIs) gradually increased or decreased in constant steps toward the end of the patterns. Four values of such steps were used in different trials: 20, 30, 45, and 60 msec. Various time-control mechanisms are hypothesized as being simultaneously responsible for subjects’ incorrect reproduction of the internal temporal ratios of the stimulus patterns. The mechanism of assimilation (of a central tendency) led subjects to enforce a regular (isochronous) structure on the patterns. The influence of other time-control mechanisms (distinction, subjective expression of an accent, sequential transfer) was expressed mainly in differences between intertap onset intervals (ITIs) and the corresponding ISIs at the beginning of the patterns. The duration of the first two ITIs was in the majority of the trials in an inverse ratio to the ratio of the respective ISIs. The distortions resulting from the timing mechanisms concerned were more pronounced in the performance of nonmusicians than in that of musicians.     

Acquisition of information from rapidly presented verbal and nonverbal stimuli

Two experiments tested recognition memory for rapidly presented stimuli. In Experiment I 16 words were presented at exposure times ranging from 25 to 500 msec followed by a yes-no recognition test. The results showed a strong dependence of memory performance on both exposure time and serial position. In Experiment II 16 random forms were presented at exposure times ranging from 125 to 2000 msec followed by a yes-no recognition test. Results for random forms showed that memory performance was strongly dependent on exposure time but not on serial position. Taken together, the results of Experiments I and II suggest qualitative encoding differences between verbal vs nonverbal stimuli.     

Allocation of cognitive processing capacity during human autonomic classical conditioning

In each of two experiments, allocation of cognitive processing capacity was measured in college-student subjects during autonomic discrimination classical conditioning. A 7.0-sec delay paradigm was used to establish classically conditioned responses to a reinforced visual conditioned stimulus (CS+). Electrodermal responses were the primary measures of autonomic classical conditioning. Allocation of processing capacity was measured by monitoring performance on a secondary reaction-time (RT) task. The auditory secondary-task RT signal was presented before, and 300, 500, 3500, 6500, and 7500 msec following CS onset. The RT signal was also presented following properly and improperly cued shock unconditioned stimuli (UCSs). Significant discrimination classical conditioning was obtained in both experiments. Comparison with control subjects who did not receive the RT signals indicated that the presence of the RT signals did not interfere with the development of classical conditioning. Four principal findings were obtained with the secondary-task RT measure. First, RTs to signals presented during CS+ were consistently slower than RTs to signals presented during CS-. This finding indicates that greater capacity allocation occurred during CS+ than CS- and is consistent with recent cognitive interpretations of classical conditioning. Second, the largest capacity allocation (i.e., slowing of RTs) occurred 300 msec following CS+ onset. This finding is consistent with the notion that subjects are actively processing the signal properties of the CS+ at 300 msec following CS+ onset. Third, presentation of the UCS when improperly cued (following CS-) significantly increased capacity allocation, whereas presentation of the same UCS when properly cued (following CS+) did not affect capacity allocation. These findings indicate that subjects were actively prepared for the UCS following CS+ but not following CS- and that a surprising UCS elicits greater capacity allocation than does an expected UCS. Fourth, large electrodermal responders to the CSs exhibited patterns of capacity allocation during the CSs, particularly during the CS+, different from those of small electrodermal responders. In particular, they exhibited significantly longer RTs at 300 msec after CS+ onset than did the small responders, followed by a shortening of RT at 500 msec relative to the small responders. This finding suggests that large electrodermal responders devote greater processing capacity to significant environmental stimuli than do small responders and that their processing may begin and be completed more rapidly. All in all, the data indicate the complexity of the cognitive processes that occur during human classical conditioning and the usefulness of the secondary-task technique in integrating conditioning theories and psychophysiology with cognitive psychology.     

The dynamic-stimulus advantage of visual symmetry perception

It has been speculated that visual symmetry perception from dynamic stimuli involves mechanisms different from those for static stimuli. However, previous studies found no evidence that dynamic stimuli lead to active temporal processing and improve symmetry detection. In this study, four psychophysical experiments investigated temporal processing in symmetry perception using both dynamic and static stimulus presentations of dot patterns. In Experiment 1, rapid successive presentations of symmetric patterns (e.g., 16 patterns per 853 ms) produced more accurate discrimination of orientations of symmetry axes than static stimuli (single pattern presented through 853 ms). In Experiments 2-4, we confirmed that the dynamic-stimulus advantage depended upon presentation of a large number of unique patterns within a brief period (853 ms) in the dynamic conditions. Evidently, human vision takes advantage of temporal processing for symmetry perception from dynamic stimuli.     

Duration discrimination of filled and empty auditory intervals: Cognitive and perceptual factors

Adult subjects were presented with two auditory stimuli per trial, and their task was to decide which of the two was longer in duration. An adaptive psychophysical procedure was used. In Experiments 1, 2, and 4, the base duration was 50 msec, whereas in Experiment 3, the base duration was 1 sec. In Experiments 1, 2, and 4, it was found that filled intervals (continuous tones) were discriminated more accurately than empty intervals (with onset and offset marked by clicks). It was concluded that this difference was perceptual rather than cognitive in nature, since performance on filled and empty intervals was not affected by increasing cognitive load in a dual-task procedure (Experiment 2) but was affected by backward masking (Experiment 4). In contrast, the results of Experiment 3 showed that duration discrimination of filled auditory intervals of longer duration was cognitively influenced, since performance was impaired by increasing cognitive load. Implications for notions of perceptual processing and timing mechanisms tanderlying differences in duration discrimination with filled and empty intervals are discussed.     

Duration discrimination of filled and empty auditory intervals: cognitive and perceptual factors.

Adult subjects were presented with two auditory stimuli per trial, and their task was to decide which of the two was longer in duration. An adaptive psychophysical procedure was used. In Experiments 1, 2, and 4, the base duration was 50 msec, whereas in Experiment 3, the base duration was 1 sec. In Experiments 1, 2, and 4, it was found that filled intervals (continuous tones) were discriminated more accurately than empty intervals (with onset and offset marked by clicks). It was concluded that this difference was perceptual rather than cognitive in nature, since performance on filled and empty intervals was not affected by increasing cognitive load in a dual-task procedure (Experiment 2) but was affected by backward masking (Experiment 4). In contrast, the results of Experiment 3 showed that duration discrimination of filled auditory intervals of longer duration was cognitively influenced, since performance was impaired by increasing cognitive load. Implications for notions of perceptual processing and timing mechanism underlying differences in duration discrimination with filled and empty intervals are discussed.