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Abstract: Stimulus uncertainty produced by variations in a target stimulus to be detected or discriminated, impedes perceptual learning under some, but not all experimental conditions. To account for those discrepancies, it has been proposed that uncertainty is detrimental to learning when the interleaved stimuli or tasks are similar to each other but not when they are sufficiently distinct, or when it obstructs the downstream search required to gain access to fine-grained sensory information, as suggested by the Reverse Hierarchy Theory (RHT). The focus of the current review is on the effects of uncertainty on the perceptual learning of speech and non-speech auditory signals. Taken together, the findings from the auditory modality suggest that in addition to the accounts already described, uncertainty may contribute to learning when categorization of stimuli to phonological or acoustic categories is involved. Therefore, it appears that the differences reported between the learning of non-speech and speech-related parameters are not an outcome of inherent differences between those two domains, but rather due to the nature of the tasks often associated with those different stimuli. [Copyright &y& Elsevier]

Background: The time course and outcome of perceptual learning can be affected by the length and distribution of practice, but the training regimen parameters that govern these effects have received little systematic study in the auditory domain. We asked whether there was a minimum requirement on the number of trials within a training session for learning to occur, whether there was a maximum limit beyond which additional trials became ineffective, and whether multiple training sessions provided benefit over a single session. Methodology/Principal Findings: We investigated the efficacy of different regimens that varied in the distribution of practice across training sessions and in the overall amount of practice received on a frequency discrimination task. While learning was relatively robust to variations in regimen, the group with the shortest training sessions (∼8 min) had significantly faster learning in early stages of training than groups with longer sessions. In later stages, the group with the longest training sessions (>1 hr) showed slower learning than the other groups, suggesting over-training. Between-session improvements were inversely correlated with performance; they were largest at the start of training and reduced as training progressed. In a second experiment we found no additional longer-term improvement in performance, retention, or transfer of learning for a group that trained over 4 sessions (∼4 hr in total) relative to a group that trained for a single session (∼1 hr). However, the mechanisms of learning differed; the single-session group continued to improve in the days following cessation of training, whereas the multi-session group showed no further improvement once training had ceased. Conclusions/Significance: Shorter training sessions were advantageous because they allowed for more latent, between-session and post-training learning to emerge. These findings suggest that efficient regimens should use short training sessions, and optimized spacing between sessions. [ABSTRACT FROM AUTHOR]

Background: Although feedback on performance is generally thought to promote perceptual learning, the role and necessity of feedback remain unclear. We investigated the effect of providing varying amounts of positive feedback while listeners attempted to discriminate between three identical tones on learning frequency discrimination. Methodology/Principal Findings: Using this novel procedure, the feedback was meaningless and random in relation to the listeners' responses, but the amount of feedback provided (or lack thereof) affected learning. We found that a group of listeners who received positive feedback on 10% of the trials improved their performance on the task (learned), while other groups provided either with excess (90%) or with no feedback did not learn. Superimposed on these group data, however, individual listeners showed other systematic changes of performance. In particular, those with lower non-verbal IQ who trained in the no feedback condition performed more poorly after training. Conclusions/Significance: This pattern of results cannot be accounted for by learning models that ascribe an external teacher role to feedback. We suggest, instead, that feedback is used to monitor performance on the task in relation to its perceived difficulty, and that listeners who learn without the benefit of feedback are adept at self-monitoring of performance, a trait that also supports better performance on non-verbal IQ tests. These results show that 'perceptual' learning is strongly influenced by top-down processes of motivation and intelligence. [ABSTRACT FROM AUTHOR]

Sensory stimuli become easier to detect or distinguish with practice. It is generally assumed that the task-relevant stimulus dimension becomes increasingly more salient as a result of attentively performing the task at a level that is neither too easy nor too difficult. However, here we show improved auditory frequency discrimination following training with physically identical tones that were impossible to discriminate. We also show that learning transfers across tone frequencies and across modalities: training on a silent visuospatial computer game improved thresholds on the auditory discrimination task. We suggest that three processes are necessary for optimal perceptual learning: sensitization through exposure to the stimulus, modality- and dimension-specific attention, and general arousal. [ABSTRACT FROM AUTHOR]

Major, rapid performance improvements in perceptual training are often dismissed as 'task' or 'procedural' learning because they are fast and generalize within a task. We assessed the contributions of perceptual and procedural learning to improvement in an auditory tone frequency learning task in humans and found that perceptual learning accounted for between 76% and 98% of the rapid early performance improvement. [ABSTRACT FROM AUTHOR]