Contribution of passive stimulus exposures to learning on auditory frequency discrimination Andrew T. Sabin and Beverly A. Wright 1
2
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Department of Communication Sciences and Disorders, the Hugh Knowles Center, Northwestern University Institute for Neuroscience, Northwestern University, Evanston IL, USA
1
Testing and Training
General Method Procedure • two-interval, forced choice, with feedback • adaptive, 3 down/1 up (79.4% correct) • 60 trials per threshold estimate Standard Stimulus used for Training • two 15-ms 1-kHz tone pips • 86 dB SPL • onsets 100 ms apart (temporal interval = 100 ms) Tasks • Frequency discrimination Which sound has the lower frequency? • Written Task Matching Symbols to Numbers 1 8 m
2 H G
3 ! h
4 h !
5 2 H
6 m !
7 E E
8 G 2
During the training phase, listeners practiced one of the following training regimens each day for 7-10 weekdays:
7
Freq PSILenceassive Silence Freq Silence Freq Silence
Freq+ Passive
8
Freq Passive Freq Passive Freq Passive
AllFreq
8
25
no training (participated only in the pre- and post-training tests)
Freq+ Silence
Freq
Freq
Freq
Freq
Freq
Freq
Freq
Freq
•
Only listeners in the Freq+Passive and AllFreq groups learned significantly more than controls on frequency discrimination at an untrained temporal interval (50 ms).
Daily Training
Group n Control 10
Untrained Temporal Interval
Pre-training
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15
•
10 5
Freq 120 trials (~ 5min) of Frequency Discrimination
Control
Freq+ Freq+ Silent Passive
AllFreq
Silence 5 minutes of the Written Task practiced in silence
of the Written Task practiced while the standard Passive 5 minutes stimulus5 was repeatedly presented in the background
Results: Trained Condition Only listeners in the Freq+Passive and All-Freq groups learned significantly more than controls on the trained condition. 25
Pre-training
1 kHz 100ms
Post-training
20
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*
15 10 5
Untrained Frequency None of the trained groups learned significantly more than controls on frequency discrimination at an untrained frequency (4 kHz). 110 100
Control
Freq+ Freq+ AllSilent Passive Freq
Pre-training Post-training
• •
These results are inconsistent with the idea that perceptual learning can only occur as a result of active performance of the target task.1-3 Instead it appears that, when mixed with active performance of the target task, additional exposures to the standard stimulus can increase learning when attention is diverted away from the target task3 and even when attention is diverted away from the standard stimulus.
We propose that active training is necessary to initiate learning, but that a period follows during which passive exposures to the standard stimulus will contribute to learning. The present results suggest that perceptual training programs could be made less effortful by including passive exposures.
Footnotes
4 kHz 100ms
Shiu and Pashler (1992) Percept. & Psychophys. 52, 582-588. 2 Ahissar and Hochstein (1993) PNAS 90, 5718-5722. 3 Wright (1998) Assoc. Res. Otolaryngol. Abs. 21: 413 4 Wright et al. (2005) Assoc. Res. Otolaryngol. Abs. 28: 428. 5 The stimuli that were presented passively always had a frequency of 1 kHz, however the temporal interval varied between 100 and 140 ms. 1
90 80 70 60 50 40
Perceptual learning can be increased by unattended exposures to the standard stimulus used in the target task. • Passive exposure to the standard stimulus, when temporally interleaved with active exposure to the same stimulus, contributed to frequency discrimination learning (a task previously shown to require some active performance for learning).3 exposures yielded the same generalization pattern as training using more than twice as many active exposures, suggesting that both types of exposures affect the same neural circuit.
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Conclusions and Discussion
• Training using a mixture of active and passive
1 kHz 50ms
Post-training
Frequency Discrimination Threshold (Hz)
We examined the influence of passive exposures to the standard stimulus (during a non-auditory task) that were interleaved with active exposures to the same stimulus (as part of a target discrimination task). We report that listeners who were not passively exposed to the standard stimulus did not learn, while those who received the passive exposures learned significantly and generalized in the same pattern as another group that actively trained on the target task for more than twice as many trials. Thus it appears that mere exposure to the standard stimulus in the same session as active performance of a target task can contribute to learning of the target task.
Before (pre) and after (post) a training phase, four groups of listeners were tested on the trained condition and several other frequency discrimination conditions.
Frequency Discrimination Threshold (Hz)
It is commonly thought that learning of a perceptual task only occurs as a result of active practice of that task.1-3 However we recently observed that learning on a target task can be increased by performing a non-target task with the same standard stimulus when both tasks are practiced in the same session.4 The purpose of this experiment was to determine whether this increased learning requires attention to the standard stimulus because it is already clear that it does not require attention to the target task.
Results: Generalization
Frequency Discrimination Threshold (Hz)
Introduction
3
Control
Freq+ Freq+ Silent Passive
AllFreq
Asterisks indicate the significance of an ANCOVA comparing the post-training performance of the trained and control listeners using pre-training performance as a covariate (computed separately for each trained group). p<0.05
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Acknowledgments K. Banai, J. Huyck, D. Karidi, J. Mossbridge, R. Wilson and Y. Zhang provided helpful comments on earlier drafts of this poster. This work was supported by NIH/NIDCD.
