Examining group differences in between-participant variability in non-native speech sound learning

Pamela Fuhrmeister

doi:10.3758/s13414-021-02311-3

Abstract

Many studies on non-native speech sound learning report a large amount of between-participant variability. This variability allows us to ask interesting questions about non-native speech sound learning, such as whether certain training paradigms give rise to more or less between-participant variability. This study presents a reanalysis of Fuhrmeister and Myers (Attention, Perception, and Psychophysics, 82(4), 2049-2065, 2020) and tests whether different types of phonetic training lead to group differences in between-participant variability. The original study trained participants on a non-native speech sound contrast in two different phonological (vowel) contexts and tested for differences in means between a group that received blocked training (one vowel context at a time) and interleaved training (vowel contexts were randomized). No statistically significant differences in means were found between the two groups in the original study on a discrimination test (a same-different judgment). However, the current reanalysis tested group differences in between-participant variability and found greater variability in the blocked training group immediately after training because this group had a larger proportion of participants with higher-than-average scores. After a period of offline consolidation, this group difference in variability decreased substantially. This suggests that the type and difficulty of phonetic training (blocked vs. interleaved) may initially give rise to differences in between-participant variability, but offline consolidation may attenuate that variability and have an equalizing effect across participants. This reanalysis supports the view that examining between-participant variability in addition to means when analyzing data can give us a more complete picture of the effects being tested.

Highlights

Many learning studies test for differences in group means as a result of some intervention: A study is typically designed so that a group of learners receives some type of treatment and they are compared to a control group or a group receiving another type of treatment
The current study presented a reanalysis of the discrimination task from Fuhrmeister and Myers (2020) to test for group differences in between-participant variability as a result of blocked or interleaved phonetic training
The current results indicate that the differences in participant variability between the groups decreased after a period of offline consolidation, which raises the question whether the group differences at the immediate posttest are important if they go away that quickly

Summary

Introduction

Many learning studies test for differences in group means as a result of some intervention: A study is typically designed so that a group of learners receives some type of treatment and they are compared to a control group or a group receiving another type of treatment. Fuhrmeister and Myers (2020) manipulated the presentation of variability (blocked vs interleaved presentation of phonological contexts) in their stimulus set to train listeners to learn a non-native segmental contrast, though this study differed from the previous ones discussed here in that they only used a limited amount of total variability in the stimulus set (i.e., this cannot be considered a high-variability training study) They found that higher pre-training aptitude predicted success with interleaved phonetic training on an identification task (though not a discrimination task). These findings provide some evidence that presenting talker or phonological variability in an interleaved manner may be a type of disequalizing treatment in non-native speech sound learning, in that high-aptitude learners benefit disproportionately. The variance of one group may be larger than the other, which could suggest an interaction with another variable that was not measured

Results

Discussion

Conclusion