Serial order effects in auditory discrimination by oddity and matching to sample

The oddity method and several matching-to-sample procedures were used for frequency and intensity discrimination by adult Ss. For all sequence tasks involving three choices, the Ss employed a decision strategy which resulted in a pattern of correctness that differed from the pattern of discriminability among the choice sounds. It was concluded that the use of signal detection theory for analysis of results had added an important dimension to the study, and it was recommended that this method of analysis be used in further attempts to relate sequential processes to various forms of verbal impairment.     

Temporal interference effects in auditory amplitude discrimination

The efficiency, y,η of performance in amplitude discrimination is examined as a function of the temporal separation, Γ, of the two signals to be discriminated. Performance in a monaural amplitude discrimination task is compared with that in a dichotic amplitude discrimination task, in which the first of the two signals was always presented to one ear and the second signal to the other ear. The difference in the shape of the resulting η versus Γ functions for the monaural and dichotic cases is interpreted in terms of peripheral and central interference effects.     

Temporal specificity of perceptual learning in an auditory discrimination task

Although temporal processing is used in a wide range of sensory and motor tasks, there is little evidence as to whether a single centralized clock or a distributed system underlies timing in the range of tens to hundreds of milliseconds. We investigated this question by studying whether learning on an auditory interval discrimination task generalizes across stimulus types, intervals, and frequencies. The degree to which improvements in timing carry over to different stimulus features constrains the neural mechanisms underlying timing. Human subjects trained on a 100- or 200-msec interval discrimination task showed an improvement in temporal resolution. This learning generalized to a perceptually distinct duration stimulus, as well as to the trained interval presented with tones at untrained spectral frequencies. The improvement in performance did not generalize to untrained intervals. To determine if spectral generalization was dependent on the importance of frequency information in the task, subjects were simultaneously trained on two different intervals identified by frequency. As a whole, our results indicate that the brain uses circuits that are dedicated to specific time spans, and that each circuit processes stimuli across nontemporal stimulus features. The patterns of generalization additionally indicate that temporal learning does not rely on changes in early, subcortical processing, because the nontemporal features are encoded by different channels at early stages.     

Temporal and spatial effects in luminance discrimination

Luminance difference thresholds (ΔI) were obtained by a successive and a simultaneous method of presenting the stimuli Spatial and temporal separation between the fields was the independent variable while other variables as stimulus size, luminance, retinal area of stimulation and duration were kept constant ΔI was less for simultaneously presented stimuli than for successively presented stimuli This was related to spatial and temporal interaction effects such that the greater the spatial interaction between simultaneously presented fields, the greater the discriminability while the greater the temporal interaction between successively presented fields, the less the sensitivity to luminance differences. It was suggested that the basis of the luminance discrimination may be different under conditions of temporal interaction than under conditions of spatial interaction between the fields.     

The effects of marker-related temporal cues on auditory gap-duration discrimination

In three experiments, we examined the ability of listeners to discriminate the duration of temporal gaps (silent intervals) and the influence of other temporal stimulus properties on their performance. In the first experiment, gap-duration discrimination thresholds were measured either in continuous noise or with noise markers with durations of 3 and 300 ms. Thresholds measured with 300-ms markers differed from those measured in continuous noise or with 3-ms markers. In the second experiment, stimuli consisting of a gap between two discrete markers were generated such that the gap duration, the onset-to-onset duration between markers, and the duration of the first marker were pseudorandomized across trials. Listeners’ responses generally were consistent with the cue that was identified as the target cue from among the three cues in each block of trials, but the data suggested that the onset-to-onset cue was particularly salient in all conditions. Using a modified method-of-adjustment procedure in the third experiment, subjects were instructed to discriminate between the durations of gaps in discrete markers of different durations in two intervals, where the gap duration in one interval was adapted to measure the point of subjective equality. Without feedback, listeners tended to equate the onset-to-onset times of the markers rather than the gap durations. Overall, the results indicated that listeners’ judgments of silent gaps between two discrete markers are strongly influenced by the onset-to-onset time, or rhythm, of the markers.     

Simultaneous auditory discrimination.

Stimuli in many visual stimulus control studies typically are presented simultaneously; in contrast the stimuli in auditory discrimination studies are presented successively. Many everyday auditory stimuli that control responding occur simultaneously. This suggests that simultaneous auditory discriminations should be readily acquired. The purpose of the present experiment was to train rats in a simultaneous auditory discrimination. The apparatus consisted of a cage with two response levers mounted on one wall and a speaker mounted adjacent to each lever. A feeder was mounted on the opposite wall. In a go-right/go-left procedure, two stimuli were presented on each trial, a wide-band noise burst through one speaker and a 2-kHz complex signal through the other. The stimuli alternated randomly from side to side across trials, and the stimulus correlated with reinforcement for presses varied across subjects. The rats acquired the discrimination in 400 to 700 trials, and no response position preference developed during acquisition. The ease with which the simultaneous discrimination was acquired suggests that procedures, such as matching to sample, that require simultaneous presentation of stimuli can be used with auditory stimuli in animals having poor vision.     

Temporal discrimination in the split brain

Divided visual field studies of neurologically normal adults indicate that the left hemisphere is superior to the right in making temporal judgments. Some neuroimaging and neuropsychological studies, however, have suggested a role for the right hemisphere in temporal processing. We tested the divided hemispheres of a split-brain patient in two tasks requiring temporal judgments about visually presented stimuli. In one task, the patient judged whether two circles presented to one visual field appeared for the same or different durations. In the second task, the patient judged whether the temporal gaps in two circles occurred simultaneously or sequentially. In both tasks, the performance of the right hemisphere was superior to that of the left. This suggests that the right hemisphere plays an important role in making temporal judgments about visually presented stimuli.     

Decay of auditory memory in vowel discrimination

Two experiments on same-different vowel discrimination are reported. In each, the main variable was the duration of a silent delay between the two items being judged. As would be expected from the assumption that such judgements depend at least partly on auditory sensory memory, longer delays led to poorer discrimination than shorter delays. The auditory memory loss seems to be asymptotic at about 3 sec, whether it is measured by correct discrimination of (as in one part of Experiment 2) by the contextual influence of the first vowel on identification of the second.     

Temporal integration in duration and number discrimination

Temporal integration in duration and number discrimination by rats was investigated with the use of a psychophysical choice procedure. A response on one lever ("short" response) following a 1-s white-noise signal was followed by food reinforcement, and a response on the other lever ("long" response) following a 2-s white-noise signal was also followed by food reinforcement. Either response following a signal of one of five intermediate durations was unreinforced. This led to a psychophysical function in which the probability of a long response was related to signal duration in an ogival manner. On 2 test days, a white-noise signal with 5, 6, 7, 8, or 10 segments of either 0.5-s on and 0.5-s off or 1-s on and 1-s off was presented, and a choice response following these signals was unreinforced. The probability of a long response was the same function of a segmented signal and a continuous signal if each segment was considered equivalent to 200 ms. A quantitative fit of a scalar estimation theory suggested that the latencies to initiate temporal integration and to terminate the process are both about 200 ms, and that the same internal accumulation process can be used for counting and timing.     

Temporal grouping in auditory spatial serial memory

Grouping effects in serial recall have been widely studied with verbal stimuli, but hardly ever with spatial stimuli and not at all with auditory spatial stimuli. In Experiment 1, we examined the influence of combined temporal and pitch grouping on recall of the locations from which bursts of white noise were presented. Similar to findings in verbal studies, effects of the grouping manipulation were found in performance accuracy, in the nature of order errors, and in the timing of responses. Experiment 2 was designed to distinguish the role played by pitch grouping from that played by temporal grouping, through independent manipulation of the presence of a shift in pitch and that of a temporal gap. The results showed that the temporal grouping manipulation determined performance and the pitch grouping manipulation did not. Similarities between our findings and those of verbal studies, and implications for the understanding of serial memory are discussed.     

Sound sequence discrimination learning motivated by reward requires dopaminergic D2 receptor activation in the rat auditory cortex

We have previously reported that sound sequence discrimination learning requires cholinergic inputs to the auditory cortex (AC) in rats. In that study, reward was used for motivating discrimination behavior in rats. Therefore, dopaminergic inputs mediating reward signals may have an important role in the learning. We tested the possibility in the present study. Rats were trained to discriminate sequences of two sound components, and licking behavior in response to one of the two sequences was rewarded with water. To identify the dopaminergic inputs responsible for the learning, dopaminergic afferents to the AC were lesioned with local injection of 6-hydroxydopamine (6-OHDA). The injection attenuated sound sequence discrimination learning, while it had no effect on discrimination between the sound components of the sequence stimuli. Local injection of 6-OHDA into the nucleus accumbens attenuated sound discrimination learning. However, not only discrimination learning of sound sequence but also that of the sound components were impaired. SCH23390 (0.2 mg/kg, i.p.), a D1 receptor antagonist, had no effect on sound sequence discrimination learning, while it attenuated the licking behavior to unfamiliar stimuli. Haloperidol (0.5 mg/kg, i.p.), a D2 family antagonist, attenuated sound sequence discrimination learning, while it had no clear suppressive effect on discrimination of two different sound components and licking. These results suggest that D2 family receptors activated by dopaminergic inputs to the AC are required for sound sequence discrimination learning.     

Zebra finches (Taeniopygia guttata) demonstrate cognitive flexibility in using phonology and sequence of syllables in auditory discrimination

Animal Cognition - Zebra finches rely mainly on syllable phonology rather than on syllable sequence when they discriminate between two songs. However, they can also learn to discriminate two...     

Perception of sequence in auditory events

A series of tape-recorded sentences were presented to various groups of listeners, totalling 164. During each sentence an extraneous sound was present on the recording, and the listener had to indicate the exact point in the sentence at which this sound occurred. It was found that errors were made which were large compared with the duration of a single speech sound; which suggests that the listener does not deal with each sound separately but rather with a group of sounds. Errors were reduced if the sentence consisted of a series of digits rather than an ordinary text, or if the listeners were trained in phonetics. Prior knowledge of the content of the sentence did not affect accuracy. The direction of error was usually to refer the extra sound to an early point, but it is affected by the relative position of the extra sound in the sentence. These results can be regarded as an extension, to the case where all stimuli are presented to the same sense, of classic results on prior entry.