El aprendizaje y la construcción de identidades

This chapter explored an account of the sound specificity effect in terms of the acoustic glimpses (intelligible left-overs) of the same word(s), created by the distinct masking of two co- occurring sounds. To this end, the present experiments created favourable and controlled “glimps- ing” contexts, where spoken words were paired with one of two car horn sounds that had the same intermittent structure and different pitches. Experiments 2A and 2B explored the hypothesis that different glimpses of the same word(s), created by the change in the paired sound from exposure to test, would elicit a sound specificity effect. The glimpse difference was realised by the change in the pitch of the paired car horn sounds. As the statistical analysis of the computationally computed glimpse percentages also demonstrated, the glimpses of the same word(s) corresponding to the two masking sounds were indeed significantly different from each other, with the low pitch car horn sound creating a higher overall glimpses percentage. Nevertheless, there was no sound specificity effect in either 2A, or 2B. The failure to find an effect in these experiments encouraged the idea to implement more contrasted glimpses of the same word(s) between exposure and test in Experiment 3. We reasoned that although different, the masking from the two background sounds in Experi- ment 2A and 2B occurred in the same word regions temporally, therefore it may have led to glimpses that were not sufficiently contrasted in eliciting the targeted effect. The high glimpse con- trast in Experiment 3 was achieved by a combined change in both the sound pitch and its temporal alignment with the word(s). The intermittent structure of the car horn sounds was particularly con- venient for both the creation of glimpsing opportunities and the manipulation of the temporal alignment between the words and their paired sounds. As anticipated, a sound specificity effect was present in the word recognition accuracy. Similar to Experiment 2A and 2B, the computed glimpses of the same words, corresponding to the two different masking sound configurations, were quanti- tatively different. I argue that what seems to be crucial for the emergence of a sound specificity effect from a glimpses perspective, is the combined quantitative and qualitative difference in the glimpses. More specifically, in Experiment 3, the two sounds masked different regions in both the frequency and temporal domains of the words, creating both quantitatively and qualitatively differ- ent glimpses of the same word(s) in exposure and test.

The comparative analysis among the experiments in this chapter revealed that the sound speci- ficity effect was not statistically different from the voice specificity effect. However, no interac- tions between the sound specificity effect in Experiment 3 and the insignificant effects in Experi- ment 2A and 2B were found. This is not entirely unexpected, considering the relatively small mag- nitude of specificity effects in general and that of the sound specificity in particular. On the other hand, there was an interaction between the voice specificity effect (Experiment 1, Chapter 2) and the insignificant effects in Experiment 2A and 2B. This suggests that the voice specificity effect seems more robust than the sound specificity effect, which is also consistent with the overall find- ings of Pufahl and Samuel (2014). It is not very surprising that indexical information pertaining to 33 human voices seems to persist better in memory than the information associated with external sounds co-existing with spoken words. The auditory system is tuned to detecting and interpreting changes in human voices as meaningful events with functional value. Tracking these changes has

Across experiments, Pufahl and Samuel (2014) found an average of about 6% decrease in the overall word identification

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accuracy as a result of the voice change from exposure to test, and an average of about 3% decrease in identification accuracy from the sound change. Similarly, we found a higher decrease in accuracy for the voice change (5.63% decrease in the overall word recognition accuracy) compared to the sound change (3.73% decrease in recognition accuracy).

useful practical and adaptive functions for successful speech understanding and communication. The functional value of tracking changes in background sounds co-occurring with spoken words, on the other hand, is arguably less relevant for the auditory system. Consistent with existing litera- ture (e.g., Pufahl and Samuel, 2014), the comparative analysis indicates that the sound specificity effect observed in Experiment 3 is fragile and less stable than its voice counterpart.

In the experiments discussed in this chapter, the fact that a specificity effect only appeared when the co-occurring sounds created highly contrasted glimpses between conditions, undermines to a certain degree the idea that mere co-occurrence between speech and sounds leads to episodic traces of the sounds in memory. Taken together, the present results indicate that energetic masking may play a role in the emergence of a sound specificity effect. As such, they support the possibility that the acoustic glimpse of a word, rather than the co-occurring sound may be retained in memory and affect subsequent word recognition accuracy. However, they do not provide enough evidence to reject the alternative that the sounds are encoded in memory alongside the words. Another plausible explanation of the present results could be that increasing the difference between the items in expo- sure and test in Experiment 3 (compared to Experiment 2A and 2B), may have led to the emergence of the sound specificity effect. Further, although these experiments present a “glimpses scenario” as a potential explanation for a sound specificity effect, they do not directly test this scenario. In all the experiments, the sounds were still present, i.e., co-occurring with the words, albeit in different masking configurations. A more direct test of the presence of glimpses in memory would have been to have another experiment with only the glimpses of the words as stimuli, instead of word-sound pairs. Without such an experiment, the glimpse hypothesis remains relatively weak.

Speech-extrinsic specificity effects are a recent phenomenon in the indexical and spoken word recognition literature, with very few studies reporting them (Cooper et al., 2015; Creel et al., 2012; Pufahl & Samuel, 2014). This recent development has the potential to add new insights into the representational nature of lexical entries and the organization of the mental lexicon. However, con- sistent with other studies that investigated speech-extrinsic specificity effects (e.g., Cooper et al., 2015; Pufahl and Samuel, 2014), the findings discussed in this chapter suggest that these effects are fragile and highly sensitive to the context in which they are tested. In the rest of the thesis, my goal is to further explore contexts in which such effects can emerge. The experiments presented here established one such context: a “glimpses” scenario. In the next chapter, I continue this investiga- tion by analyzing the analogy (or lack thereof) between voice specificity and sound specificity, fo- cusing on the notion of integrality (Vitevitch, 2003), that is, the degree to which spoken words are necessarily undissociable from the accompanying voice as opposed to the accompanying sound.