Influence of temporal masking on click-pair discriminability

When temporal auditory acuity is estimated using time-reversed click pairs, the asymmetry of temporal masking may influence the results. To investigate this hypothesis, we first established normal-hearing listeners’ psychometric functions for the discrimination of time-reversed click pairs. An attempt to relate listeners’ performances in click-pair discrimination to their performances in forward and backward masking tasks was unsuccessful, probably due to the presence of spectral artifact in the temporal masking paradigms. We then investigated listeners’ abilities to discriminate time-reversed click pairs in which the intensity of the lower level click in one pair was altered. This alteration was introduced at random in order to minimize the influence of spectral artifact. Our results suggest that the course of temporal masking influenced the discriminability of the modified click pairs. Thus, the discrimination of time-reversed click pairs may yield a biased estimate of auditory temporal acuity.     

Temporal information processing and pitch discrimination as predictors of general intelligence.

In the present study, the relationship between performance on temporal and pitch discrimination and psychometric intelligence was investigated in a sample of 164 participants by means of an experimental dissociation paradigm. Performance on both temporal and pitch discrimination was substantially related to psychometric intelligence (r=.43 and r =.39). Regression analysis and structural equation modeling suggested that both psychophysical domains can be considered as valid predictors of psychometric intelligence. Both predictor variables contributed substantial portions of both shared and unique variance to the prediction of individual differences in psychometric intelligence. Thus, the present study yielded further evidence for a functional relationship between psychometric intelligence and temporal as well as pitch discrimination acuity. Eventually, findings are consistent with the notion that temporal discrimination - in addition to general aspects of sensory discrimination shared with pitch discrimination reflects specific intelligence-related aspects of neural information processing.     

Stable individual differences in number discrimination in infancy

Previous studies have shown that as a group 6-month-old infants successfully discriminate numerical changes when the values differ by at least a 1:2 ratio but fail at a 2:3 ratio (e.g. 8 vs. 16 but not 8 vs. 12). However, no studies have yet examined individual differences in number discrimination in infancy. Using a novel numerical change detection paradigm, we present more direct evidence that infants' numerical perception is ratio-dependent even within the range of discriminable ratios and thus adheres to Weber's Law. Furthermore, we show that infants' numerical discrimination at 6 months reliably predicts their numerical discrimination abilities but not visual short-term memory at 9 months. Thus, individual differences in numerical discrimination acuity may be stable within the first year of life and provide important avenues for future longitudinal research exploring the relationship between infant numerical discrimination and later developing math achievement.     

Forgetting and conditioned suppression: role of a temporal discrimination

Several experiments have found complete retention of conditioned suppression when overall suppression to the signal for shock was measured. The present experiment examined retention of conditioned suppression but did so with a paradigm that produced temporal discrimination of shock occurrence. Nine rats were exposed to a flashing light signal of 5-min duration that always terminated with a shock. After several months, a temporal discrimination was well established, as shown by maximum suppression toward the end of the signal period. After remaining in the home cage for 25 days, the rats were again subjected to the conditioning procedure. The overall level of suppression remained the same but the temporal discrimination was not observed.     

Discrimination of stimulus aperiodicity as a function of temporal patterning: a discrepancy between psychophysical and sensory-neural assessments.

Tactile discrimination of stimulus aperiodicity was investigated in a two-alternative forced-choice task by having subjects report which of two successively presented trains of mechanical pulses, one with complete pulse periodicity and one in which a single pulse was temporally displaced from its regular placement, was temporally irregular or aperiodic. Trains contained three, four, or five pulses and were presented at interpulse intervals of 60, 75, 85, 100, 125, and 150 ms. Aperiodic trains had one pulse, other than the first or last pulse, temporally advanced or receded by 40% of the interstimulus interval. Results showed that: (i) although the percentage of correct reports of aperiodicity decreased as presentation rate increased (smaller interpulse intervals), the amount of decrease was a function of the number of pulses in a train; (ii) the discrimination of aperiodicity was dependent upon the specific location of the irregularity within the stimulus temporal pattern; and (iii) all patterns with complete temporal reversals of their successive interpulse intervals yielded nearly equivalently accurate reports of aperiodicity. These data suggest that central, attentional factors are involved in the discrimination of stimulus aperiodicity.     

Effects of the build-up and resetting of auditory stream segregation on temporal discrimination

The tendency to hear a tone sequence as 2 or more streams (segregated) builds up, but a sudden change in properties can reset the percept to 1 stream (integrated). This effect has not hitherto been explored using an objective measure of streaming. Stimuli comprised a 2.0-s fixed-frequency inducer followed by a 0.6-s test sequence of alternating pure tones (3 low [L]-high [H] cycles). Listeners compared intervals for which the test sequence was either isochronous or the H tones were slightly delayed. Resetting of segregation should make identifying the anisochronous interval easier. The HL frequency separation was varied (0-12 semitones), and properties of the inducer and test sequence were set to the same or different values. Inducer properties manipulated were frequency, number of onsets (several short bursts vs. one continuous tone), tone:silence ratio (short vs. extended bursts), level, and lateralization. All differences between the inducer and the L tones reduced temporal discrimination thresholds toward those for the no-inducer case, including properties shown previously not to affect segregation greatly. Overall, it is concluded that abrupt changes in a sequence cause resetting and improve subsequent temporal discrimination.     

Duration discrimination in the context of age,sex, and cognition

It has been proposed that the perception of very short duration is governed by sensory mechanisms, whereas the perception of longer duration depends on cognitive capacities. Four duration discrimination tasks (modalities: visual, auditory; base duration: 100 ms, 1000 ms) were used to study the relation between time perception, age, sex, and cognitive abilities (alertness, visual and verbal working memory, general fluid reasoning) in 100 subjects aged between 21 and 84 years. Temporal acuity was higher (Weber fractions are lower) for longer stimuli and for the auditory modality. Age was related to the visual 100 ms condition only, with lower temporal acuity in elder participants. Alertness was significantly related to auditory and visual Weber fractions for shorter stimuli only. Additionally, visual working memory was a significant predictor for shorter visual stimuli. These results indicate that alertness, but also working memory, are associated with temporal discrimination of very brief duration.     

An orientation illusion analog to the rod and frame: Relational effects in the magnitude of the distortion

In previous studies, we have measured individual differences in simultaneous brightness discrimination between a long-duration (500 msec or more) comparison pulse and a set of briefer test pulses of the same luminance. Some observers judge the comparison pulse to be brighter than all test pulses in a range from 20 to 320 msec. Other observers exhibittemporal brightness enhancement: a test pulse of 80 msec for our stimulus conditions is judged brighter than the comparison pulse. Individual differences depend upon the temporal asynchrony between test and comparison pulses. Observers designated Type A show temporal brightness enhancement for both simultaneous onset of test and comparison pulse and for simultaneous offset of the pulses. Type B observers exhibit brightness enhancement for simultaneous offset of pulses but not for simultaneous onset. Type C observers do not exhibit brightness enhancement effects. Here we use both short (80 msec) and long (640 msec) pulses as the comparison stimuli. We replicate our previous pattern of individual differences for the long comparison stimulus. For the short comparison stimulus, brightness discrimination functions for the three classes of observers are exactly predicted from the patterns obtained with the conventional long comparison pulse. This confirms the generality of individual differences in pulse brightness perception and shows that they do not depend upon the particular stimulus conditions selected for the discrimination task.     

Effects of retinal eccentricity and acuity on global-motion processing

The present study assessed direction discrimination with moving random-dot cinematograms at retinal eccentricities of 0, 8, 22, and 40?deg. In addition, Landolt-C acuity was assessed at these eccentricities to determine whether changes in motion discrimination performance covaried with acuity in the retinal periphery. The results of the experiment indicated that discrimination thresholds increased with retinal eccentricity and directional variance (noise), independent of acuity. Psychophysical modeling indicated that the results for eccentricity and noise could be explained by an increase in channel bandwidth and an increase in internal multiplicative noise.     

Temporal order and processing acuity of visual,auditory, and tactile perception in developmentally dyslexic young adults

We studied the temporal acuity of 16 developmentally dyslexic young adults in three perceptual modalities. The control group consisted of 16 age- and IQ-matched normal readers. Two methods were used. In the temporal order judgment (TOJ) method, the stimuli were spatially separate fingertip indentations in the tactile system, tone bursts of different pitches in audition, and light flashes in vision. Participants indicated which one of two stimuli appeared first. To test temporal processing acuity (TPA), the same 8-msec nonspeech stimuli were presented as two parallel sequences of three stimulus pulses. Participants indicated, without order judgments, whether the pulses of the two sequences were simultaneous or nonsimultaneous. The dyslexic readers were somewhat inferior to the normal readers in all six temporal acuity tasks on average. Thus, our results agreed with the existence of a pansensory temporal processing deficit associated with dyslexia in a language with shallow orthography (Finnish) and in well-educated adults. The dyslexic and normal readers' temporal acuities overlapped so much, however, that acuity deficits alone would not allow dyslexia diagnoses. It was irrelevant whether or not the acuity task required order judgments. The groups did not differ in the nontemporal aspects of our experiments. Correlations between temporal acuity and reading-related tasks suggested that temporal acuity is associated with phonological awareness.     

Dissociation of explicit and implicit timing in repetitive tapping and drawing movements

Four experiments explored the hypothesis that temporal processes may be represented and controlled explicitly or implicitly. Tasks hypothesized to require explicit timing were duration discrimination, tapping, and intermittent circle drawing. In contrast, it was hypothesized that timing control during continuous circle drawing does not rely on an explicit temporal representation; rather, temporal control is an emergent property of other control processes (i.e., timing is controlled implicitly). Temporal consistency on the tapping and intermittent drawing tasks was related, and performance on both of these tasks was correlated with temporal acuity on an auditory duration discrimination task. However, timing variability of these 3 tasks was not correlated with timing variability of continuous circle drawing. These results support the hypothesized distinction between explicit and implicit temporal representations.     

Attentional breadth and trade-offs in spatial and temporal acuity

Various manipulations have been shown to induce trade-offs in spatial and temporal acuity. Two experiments examine the role of the breadth of the attentional focus in such trade-offs. In the first experiment, exogenous attentional cues indicated 1, 2, 3, or 4 possible (contiguous) target locations. Half of the subjects performed a perceptual task on the target requiring spatial acuity – detecting spatial gaps in a ring; the other half of the subjects performed a task requiring temporal acuity – detecting a temporal gap in the presentation of the target ring. The results revealed a trade-off in spatial and temporal acuity: as the cue size increased, performance on the spatial task declined and performance on the temporal task improved. A second experiment replicated this pattern using two different tasks: a temporal order judgment task that assessed temporal acuity, and a task requiring the localization of a thin line that assessed spatial acuity.     

The detection of a temporal gap between two disparate stimuli

When a temporal gap is bounded by a light and a tone, gap detection performance as a function of gap duration is well described by a simple model which characterizes the discrimination as a purely temporal one. When the gap is bounded by two tones, performance is superior and seems to depend on the frequency difference between the tones, but is not well described by the same model. It is suggested that the light-tone performance represents the operation of a central temporal discrimination mechanism, while the tone-tone cases represent the use by Os of nontemporal cues originating in the peripheral auditory system.     

On the refractoriness of somesthetic temporal acuity

Preconditioning, with a burst of electrical pulse stimuli elevates the threshold for temporal acuity as measured with a technique requiring the S to detect a short gap in an otherwise regular burst of similar stimuli. Only a small amount of backward inhibition can be observed. The temporal duration of the inhibitory effect (up to 700 msec.) suggests that repetitive after-discharges of second-order afferents in Ike spinal cord may underlie this behavioral measure by actually filling in the intervals which are used by the S to make the judgment. The phenomenon is thus thought to be a disruption of a true temporal judgment rather than one indirectly mediated by an amplitude judgment, and as such it represents a significant datum on the temporal resolving power of time dimensions of neural coding.     

The detectability of a brief gap in a pulse of light as a function of its temporal location within the pulse

A signal detection experiment was carried out to test the hypothesis that the detectability of abrief gap of fixed duration in a pulse of light would vary with its temporal location in the pulse. For five of six Os, as the gap occurred later and later in the pulse, gap detectability increased until just prior to the end of the pulse, where a sharp decrease was found. The finding was replicated in a seventh O and the decrease in detectability near the end was found to be attributable to the temporal proximity of the end of the pulse. The results are interpreted in terms of the effects of light adaptation and masking.     

Vibrotactile frequency discrimination

Thresholds for vibrotactile discrimination of pulse interval were determined for pulse frequencies between 1 and 384 Hz. The results point to a temporal resolution significantly more accurate than that demonstrated in earlier studies. Although touch as a vibratory sensor is in general much inferior to audition, the present results show a striking resemblance to those obtained on auditory pitch. The neurophysiological implications for the tactile as well as for the auditory system are discussed.     

Duration discrimination of brief light flashes

The data from four experiments indicate that when Os discriminate between light flashes of different durations, for durations for which Bloch’s law has been shown to hold, their discriminations are frequently made on the temporal information available in the flashes rather than on their apparent brightness. A model for duration discrimination which specifies that discriminability depends only on the difference in duration between the two brief flashes, and is independent of their durations, is presented and applied to the data.     

Temporal preparation facilitates perceptual identification of letters

Recent evidence has suggested that perceptual processing of single stimulus features improves when participants are temporally prepared for the occurrence of the stimuli. This study was conducted to investigate whether the benefit of temporal preparation generalizes to perceptual identification of more complex stimuli, such as letters. In three experiments, participants discriminated masked letters under high- and low-temporal-preparation conditions. Visual discrimination performance in all experiments improved when the participants were temporally prepared. Therefore, the present results support the notion that perception benefits from temporal preparation not only at the feature level, but also at subsequent levels at which feature information is integrated.     

The spatial constraint in intersensory pairing: no role in temporal ventriloquism

A sound presented in temporal proximity to a light can alter the perceived temporal occurrence of that light (temporal ventriloquism). The authors explored whether spatial discordance between the sound and light affects this phenomenon. Participants made temporal order judgments about which of 2 lights appeared first, while they heard sounds before the 1st and after the 2nd light. Sensitivity was higher (i.e., a lower just noticeable difference) when the sound-light interval was approximately 100 ms rather than approximately 0 ms. This temporal ventriloquist effect was unaffected by whether sounds came from the same or a different position as the lights, whether the sounds were static or moved, or whether they came from the same or opposite sides of fixation. Yet, discordant sounds interfered with speeded visual discrimination. These results challenge the view that intersensory interactions in general require spatial correspondence between the stimuli.     

Temporal expectancy modulates inhibition of return in a discrimination task

This research examined the influence of cue temporal predictability on inhibition of return (IOR) in a discrimination task. In exogenous attention experiments, the cue that summons attention is noninformative as to where the target will appear. However, it is predictive as to when it will appear. In previous work, it was demonstrated that temporal predictability does not influence IOR in detection tasks. In this work, it is shown that IOR is influenced by temporal predictability in discrimination tasks. Predictability was manipulated by using three stimulus onset asynchrony distributions: nonaging, aging, and accelerated aging. IOR was found when the cue predicted target appearance and was modulated by temporal information. In the nonaging distribution (in which the cue did not predict target appearance), there was no IOR.