The role of phonetic naturalness in biasing the learning of sound patterns remains an unsettled question in phonology. The present study investigates naturalness bias in phonotactic learning using a novel experimental paradigm that tests whether learners reproduce a phonetically-motivated phonotactic implicational about the distribution of major place contrasts in stops. Stops differing in place of articulation are easier to distinguish word-initially than word-finally, so place contrasts in word-final position should also exist in word-initial position. The reverse is not necessarily true. This implicational is typologically supported as well as motivated by perceptual naturalness. In two artificial grammar learning experiments, I exposed participants to place contrasts in stops either word-initially or word-finally and tested whether they extended the contrasts to the other word-edge position. Participants successfully learned to recognize novel words that fit the phonotactic pattern they had been trained on, but they were equally willing to extend the place contrasts in both directions, yielding no evidence for naturalness bias. These results contrast with those of a similar study that found asymmetric extension of the stop voicing contrast, supporting an effect of naturalness bias. Confusion data suggests that the reduction in perceptibility from word-initial to word-final position may be greater for stop voicing than for stop place of articulation. This difference may underlie the divergent results of the two studies, leading to the hypothesis that the strength of a substantive bias depends on the magnitude of its phonetic precursor.
Crosslinguistically, phonological patterns tend to be phonetically natural, meaning they are motivated by articulatory and perceptual phonetic tendencies (
In arguing in favor of its existence, proponents of substantive bias have primarily relied on experimentation, particularly artificial grammar learning (AGL). If participants (infants, children, or adults) learn phonetically natural patterns better than phonetically unnatural patterns in AGL experiments, this provides evidence for a cognitive bias against acquiring phonetically unnatural patterns that may play a role in addition to the diachronic channel bias. The picture is currently inconclusive, however, because while some AGL experiments have uncovered learning advantages for phonetically motivated patterns (e.g.
There are a number of potential explanations for why substantive bias effects are so elusive in AGL studies. If substantive bias is relatively subtle (and/or difficult for current AGL methodologies to detect), then it may only be uncovered in very sensitive experiments. In this case, we expect fairly frequent null results, and it is the steady accumulation of solid positive results that would prove that substantive bias does influence learners. On the other hand, if there is no synchronic bias against unnatural phonological patterns, then the positive results in the AGL literature must be spurious. Publication bias may have inflated their relative frequency, with studies finding effects in the opposite direction of substantive bias potentially going unreported. Null results may also be underreported relative to their actual incidence. Between these two poles (substantive bias exists vs. there is no substantive bias), there could be more nuanced proposals. It might be that not all phonetic precursors to natural phonological patterns (i.e. perceptual or articulatory facts that make the patterns phonetically natural, perhaps in comparison to other logically possible patterns) give rise to substantive biases. Glewwe et al. (
This paper presents an AGL study testing for substantive bias in phonotactic learning. In two experiments, I exposed learners to major place contrasts in stops in either word-initial or word-final position and tested whether they extended the contrasts to the other word-edge position. Naturalness bias predicts that learners should extend such contrasts more from word-final position to word-initial position than vice versa, but in fact participants in my experiments extended equally in both directions. While this study cannot definitively distinguish between the abovementioned theories about why it is difficult to obtain substantive bias effects in AGL experiments, it can make a contribution. First, it represents another case of a null substantive bias result, helping to mitigate a potential publication bias. It is also useful to know
In the remainder of the paper, I introduce the phonotactic implicational that underpins the experiments (Section 2) and present the AGL study itself (Section 3). I then contrast its results with those of an analogous study (
Past work on naturalness bias effects in phonological learning has looked more often at alternations than at phonotactics. When AGL experiments test for naturalness bias in phonotactic learning, they typically expose participants to stimuli that provide negative evidence for a particular phonotactic constraint (e.g. *[α round][–α round] in
The positional extension I tested is rooted in a phonotactic implicational concerning the positional distribution of major place contrasts. If a language has major place contrasts in stops post-vocalically/in coda position (e.g. /ap/ vs. /at/ vs. /ak/), it should also have major place contrasts in stops pre-vocalically/in onset position (e.g. /pa/ vs. /ta/ vs. /ka/), but not necessarily vice versa (
The phonotactic implicational about the distribution of major place contrasts appears to hold crosslinguistically. Steriade (
If phonetic knowledge influences learners’ acquisition of phonological patterns and learners are biased toward phonetically natural phonological systems, they should make inferences about language in accordance with phonotactic implicationals like this one. Consequently, I used the phonotactic implicational about the distribution of stops with different places of articulation to structure an AGL study testing for substantive bias.
In Experiment 1, I exposed participants to artificial languages featuring a three-way place contrast in either word-initial (pre-vocalic) or word-final (post-vocalic) position and tested whether they assumed the contrast existed in the other position as well. If participants behave in a way that is consistent with substantive bias, they will extend the place contrasts more from word-final to word-initial position than from word-initial to word-final position.
The first part of the experiment involved listening to words associated with pictures. There were two training conditions, Initial Contrast and Final Contrast. In the Initial Contrast condition, participants heard words beginning with labial, coronal, and dorsal stops (e.g.
I chose coronal place of articulation for the position in which stops did not contrast in place because coronal place is commonly considered unmarked (
O’Hara’s (
On the other hand, expanding the typological picture to languages like Selayarese introduces further complications. Although [ʔ] is the stop with the least marked place of articulation (
While Steriade (
Returning to the conditions, then, the Initial Contrast language is natural in that it features major place contrasts in stops word-initially but not word-finally, a pattern consistent with the phonotactic implicational. The Final Contrast language, on the other hand, is unnatural: in having major place contrasts word-finally but not word-initially, it violates the implicational.
Experiment 1 training conditions.
✔ | ✔ | ✔ | ✖ | ✔ | ✖ | |
✖ | ✔ | ✖ | ✔ | ✔ | ✔ |
The test items were identical in the two conditions. In the test phase, participants in both the Initial Contrast and Final Contrast conditions heard words beginning and ending with labial, coronal, and dorsal stops.
The training and test items were all nonce words of the shape C1VC2VC3. Either C1 or C3 was a stop drawn from [p t k b d ɡ]. The other two Cs were sonorants drawn from [n l ɹ j w]. The glides [j] and [w] did not occur word-finally, and no item contained a [ji] or [wu] sequence. In each word, all three Cs were different. The vowels were drawn from [i ɑ u]. Labial, coronal, and dorsal stops were equally represented in the position with the place contrasts in training and across positions in test. Additionally, voiced and voiceless stops were equally represented across positions and places of articulation in both the training and test phases. In the Initial Contrast condition, half the training items with initial stops were members of minimal triplets (e.g.
Sample training items in the Initial Contrast condition.
jáwi |
The stimuli were recorded by a phonetically-trained male native speaker of American English who was naïve to the purpose of the experiment. Voiced stops were fully voiced, voiceless stops were aspirated, and word-final stops were released. Unstressed vowels were not reduced. Otherwise, pronunciation was as in American English. The stimuli were produced in isolation as if each item was a sentence unto itself. The stimuli were recorded in a sound-attenuated room using a head-mounted microphone. Recording was done using Audacity with a sampling rate of 22,050 Hz.
The experiment was conducted online using Experigen (
The experiment began with the training phase (see
Event sequence for one training trial.
Event sequence for one test trial.
There were three types of item in the test phase. While the same set of test items was used in both conditions, which types test items fell into depended on the condition. Familiar Conforming items contained stops whose place of articulation and position conformed to the trained pattern (e.g. #P, #T, #K, and T# in the Initial Contrast condition) and were words that were heard in training. Novel Conforming items also contained stops whose place of articulation and position conformed to the trained pattern, but these words had not been heard in training. Finally, Novel Nonconforming items featured the place of articulation and position combinations not heard in training (e.g. P# and K# in the Initial Contrast condition). In each condition, there were 16 Familiar Conforming items, 16 Novel Conforming items, and 16 Novel Nonconforming items.
Sample test items for each training condition in Experiment 1.
nálu |
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rujá |
nálu |
The participants were native English speakers recruited through the UCLA Psychology Subject Pool. I excluded participants who reported that they were not in fact native English speakers (12), had taken more than one linguistics class (7), reported a history of speech or hearing impairments (4), gave an incorrect response to either of the two test words that preceded the experiment (0 in Experiment 1), or accepted all test items (2). After exclusions (25 out of 75 participants), there were 25 participants in each condition.
While not central to the research question, a first prediction is that the acceptance rate of Familiar Conforming items should be greater than the acceptance rate of Novel Conforming items. In other words, participants should accept words they heard in the training phase more often than they accept words that fit their training pattern but are new to them.
Participants’ acceptance rates of Novel Nonconforming items, relative to Novel Conforming items, indicate whether they have extended the place contrasts in stops to a new position in a given condition. For instance, if participants in the Initial Contrast condition accept test items with word-final labial and dorsal stops (P# and K#), they have extended the word-initial place contrasts they encountered in training to word-final position. Recall the phonetic advantage favoring word-initial place contrasts: stop place of articulation is more perceptible at the beginning of a word than at the end of a word. On the basis of phonetic naturalness, then, a language with major place contrasts word-finally should also have major place contrasts word-initially, but not necessarily the other way around. Performance consistent with a substantive bias would be asymmetric extension: participants exposed to the place contrasts word-finally should extend them to word-initial position more than participants exposed to the place contrasts word-initially extend them to word-final position. Extension of the place contrasts to the other position manifests as erroneously accepting Novel Nonconforming items, so participants trained on the contrasts word-finally should more readily accept their Novel Nonconforming items (#P and #K) than participants trained on the contrasts word-initially accept their own Novel Nonconforming items (P# and K#).
Assuming similar performance in both conditions on Novel Conforming items, meaning that participants in both conditions learned to an equal degree what types of words did belong to their language, a higher acceptance rate of Novel Nonconforming items in the Final condition relative to the Initial Contrast condition would constitute evidence that learners are biased toward phonetically natural phonotactic systems. Put another way, if learning is substantively biased, participants should learn the unnatural Final Contrast language worse than the natural Initial Contrast language, as demonstrated by their mistakenly “filling in” the missing initial labial and dorsal stops in their language.
Acceptance of test items by condition.
I analyzed the results with mixed-effects logistic regressions using the
Experiment 1—fixed effects of the conforming items model.
Intercept | 0.547 | 0.214 | 2.552 | 0.011* |
Familiarity = familiar (vs. novel) | 1.526 | 0.291 | 5.242 | <0.001*** |
Condition = Final Contrast (vs. Initial Contrast) | –0.167 | 0.266 | –0.630 | 0.529 |
Familiarity × Condition | –0.157 | 0.339 | –0.464 | 0.643 |
Turning now to novel items, the acceptance rates of Novel Conforming items were significantly above chance in both conditions, meaning that both Initial Contrast and Final Contrast participants correctly generalized to new words in their language. The acceptance rates of Novel Nonconforming items were significantly below chance in both conditions, meaning that both Initial Contrast and Final Contrast participants correctly rejected words not in their language.
I fit a mixed-effects logistic regression to the novel items (Novel Conforming and Novel Nonconforming) with response (accept or reject) as the dependent variable, Conformity (conforming vs. nonconforming), Condition (Initial Contrast vs. Final Contrast), and their interaction as fixed effects, random intercepts for subject and item, and by-subject random slopes for Conformity. The model was dummy coded with nonconforming as the reference level for Conformity and Initial Contrast as the reference level for Condition.
Experiment 1—fixed effects of the novel items model.
Intercept | –0.520 | 0.221 | –2.354 | 0.019* |
Conformity = conforming (vs. nonconforming) | 1.094 | 0.241 | 4.534 | <0.001*** |
Condition = Final Contrast (vs. Initial Contrast) | –0.057 | 0.309 | –0.185 | 0.853 |
Conformity × Condition | –0.116 | 0.356 | –0.326 | 0.744 |
In sum, participants did not fill in the place of articulation gaps in their training languages; rather, in both conditions, they successfully learned the gaps. The lack of interactions in the regression models means that there was no difference in participants’ ability to generalize to new words or reject nonconforming words between the conditions.
The participants in Experiment 1 did not reproduce the phonotactic implicational about the positional distribution of major place contrasts. That is, they did not extend the place contrasts more from word-final to word-initial position than from word-initial to word-final position. The experiment therefore yielded no evidence for substantive bias. Note that this was not because the experiment itself was entirely insensitive: it did uncover strong effects of familiarity and learning of the trained pattern. This suggests that if the relevant substantive bias does influence phonotactic learning, its effect must be much smaller than the effects the experiment was able to detect.
Another reason no substantive bias effect emerged could be that participants’ learning was too explicit because the pattern was too easy to identify. Moreton & Pertsova (
Moreton & Pertsova (
While Experiment 1 already incorporates design properties previously used to foster implicit learning and partly resembles Moreton & Pertsova’s No-Feedback (implicit learning) condition in its results, Moreton & Pertsova demonstrated that participants may engage in explicit learning even in an experiment meant to encourage implicit learning. They also showed that changing properties of an experiment can affect what kind of learning participants engage in. Thus, even if Experiment 1 elicited a certain amount of implicit learning, it should still be possible to make learning even more implicit.
I hypothesized that making the task in Experiment 1 harder might foster more implicit learning, which might in turn cause substantive bias to emerge. To test this, I carried out Experiment 2, a modified version of the positional extension of place contrasts experiment.
Experiment 2 was identical to Experiment 1 except for three differences. First, I added 20 filler items in which all three consonants were sonorants (e.g.
Second, I increased the number of training blocks from two to three. This was done because the acceptance rate of Novel Conforming items in the Final Contrast condition was just barely significantly above chance in Experiment 1. Acceptance rates of Novel Conforming items must be above chance to show that participants have learned to accept the types of items they were trained on. Without this demonstration of learning, performance on Novel Nonconforming items is harder to interpret. I therefore increased the number of training blocks in Experiment 2 to try to push Novel Conforming acceptance rates up.
Finally, I removed the Familiar Conforming items from the test phase, leaving 32 test items in each condition.
The participants in Experiment 2 were native English speakers recruited through the UCLA Psychology Subject Pool. I applied the same exclusion criteria as in Experiment 1 and excluded 25 out of 67 participants. Of the 25 excluded participants, 10 were not in fact native English speakers, 7 had taken more than one linguistics class, 1 reported a history of speech or hearing impairments, and 7 gave an incorrect response to either of the two test words that preceded the experiment. After exclusions, there were 21 participants in each condition. None of the participants in Experiment 2 had participated in Experiment 1.
The predictions for Experiment 2 are the same as the predictions for Experiment 1, except that Familiar Conforming items are not predicted to be accepted more than Novel Conforming items because there are no Familiar Conforming items. If learners are biased toward phonetically natural phonotactic systems, participants in the Final Contrast condition should more readily accept Novel Nonconforming items than participants in the Initial Contrast condition. This would show that learners are more likely to assume place contrasts exist word-initially if they have been taught they exist word-finally than they are to assume place contrasts exist word-finally if they have been taught they exist word-initially. If there is no substantive bias at work, acceptance rates of Novel Nonconforming items should not differ between the two conditions.
Acceptance of test items by condition.
For Novel Nonconforming items, the mean acceptance rates in Experiment 1 were 39% in the Initial Contrast condition and 38% in the Final Contrast condition while the mean acceptance rates in Experiment 2 were 50% in the Initial Contrast condition and 48% in the Final Contrast condition. Eliminating the Familiar Conforming test items also pushed up acceptance rates of Novel Nonconforming items. In Experiment 1, Novel Nonconforming items were accepted at rates significantly below chance in both conditions, but in Experiment 2, the acceptance rates of Novel Nonconforming items did not differ from chance in either condition.
To test for asymmetric positional extension of the place contrasts, I fit a mixed-effects logistic regression to the test items (Novel Conforming and Novel Nonconforming) with response (accept or reject) as the dependent variable, Conformity (conforming vs. nonconforming), Condition (Initial Contrast vs. Final Contrast), and their interaction as fixed effects, random intercepts for subject and item, and by-subject random slopes for Conformity.
Experiment 2—fixed effects of the model.
Intercept | –0.032 | 0.268 | –0.121 | 0.904 |
Conformity = conforming (vs. nonconforming) | 0.771 | 0.337 | 2.286 | 0.022* |
Condition = Final Contrast (vs. Initial Contrast) | –0.031 | 0.375 | –0.081 | 0.935 |
Conformity × Condition | 0.319 | 0.501 | 0.637 | 0.524 |
Like Experiment 1, Experiment 2 found robust learning of the phonotactic patterns: participants clearly distinguished between conforming and nonconforming novel words. Experiment 2 also resembles Experiment 1 in its lack of a significant interaction of Conformity and Condition, meaning that there was no asymmetric extension of the place contrasts. Participants in the Final Contrast condition did not extend the place contrasts more from word-final to word-initial position than participants in the Initial Contrast condition extended the place contrasts from word-initial to word-final position. Experiment 2 thus did not yield evidence for substantive bias either. Though the actual acceptance rates of Novel Conforming and Novel Nonconforming items changed from Experiment 1 to Experiment 2 due to the removal of the Familiar Conforming items, the natural Initial Contrast language and the unnatural Final Contrast language were still learned equally well.
The main motivation for running Experiment 2 was to try to make participants’ learning more implicit and thereby allow a substantive bias to emerge. To foster implicit learning, I added filler items to the training phase in hopes of making the distribution of labial, coronal, and dorsal stops less obvious. One might ask whether this modification actually caused more implicit learning in Experiment 2 as compared to Experiment 1. In Experiment 2, roughly half of participants (10 out of 21 (48%) in the Initial Contrast condition and 11 out of 21 (53%) in the Final Contrast condition) reported seeking a rule to distinguish words in their language from those not in their language. Only one participant in each condition found the correct rule. In Experiment 1, two thirds (Initial Contrast condition) or three quarters (Final Contrast condition) of participants reported seeking a rule, so there does seem to have been somewhat more implicit learning in Experiment 2. This did not lead to the emergence of substantive bias, however. The natural and unnatural patterns were still learned to an equal degree.
The basis of this study was the phonotactic implicational whereby major place contrasts in post-vocalic position entail major place contrasts in pre-vocalic position, but not vice versa. Together, Experiments 1 and 2 show that this implicational is not reproduced in an AGL paradigm. Instead, participants learned equally well a natural language in which place was contrasted in stops only word-initially and an unnatural language in which place was contrasted in stops only word-finally. Neither experiment’s results provide support for substantive bias. Though Experiment 2 may have successfully encouraged more implicit learning, it still did not turn up evidence for substantive bias.
Experiments 1 and 2 tested for substantive bias in phonotactic learning by investigating whether learners were more likely to extend phonemic contrasts from a position in which they were less perceptible to a position in which they were more perceptible than vice versa. Such asymmetric extension would support the hypothesis that phonetic naturalness biases phonological learning, but it was absent in the experiments. Interestingly, Glewwe (
The experiments in Glewwe (
Acceptance of Novel Nonconforming items by experiment and condition.
In Glewwe’s (
Given the great similarity between the two sets of experiments, these divergent results are surprising. Glewwe (
One possible explanation for why a substantive bias effect emerged in the voicing contrast study but not in the place contrasts study would be a difference between voicing and place of articulation in terms of the size of the perceptibility differential across positions. If the difference between the perceptibility of stop voicing word-initially and word-finally is greater than the difference between the perceptibility of stop place word-initially and word-finally, then having a contrast only in word-final position, where it is harder to hear, should be more unnatural in the case of voicing than in the case of place of articulation, leading to more positional extension of the voicing contrast. If the perceptibility differential across word-edge positions is smaller for place of articulation, meaning that place contrasts in stops are only marginally harder to hear word-finally than word-initially, then there may be less pressure to avoid the unnatural sound pattern via positional extension, resulting in no effect in the present study.
White (
For this type of explanation to account for the difference between the current study and Glewwe’s (
Wang & Bilger (
Consonant confusions in the CV context (added across all signal levels).
Consonant confusions in the VC context (added across all signal levels).
As
These confusion data do provide evidence that the decrease in perceptibility from word-initial position to word-final position is greater for stop voicing than for stop place, which in turn could explain why substantive bias emerged in Glewwe’s (
The evidence from Wang & Bilger should be treated with caution, though, because as a reviewer points out, they considered the confusability of these stops not just amongst themselves but with all the obstruents of English. On the one hand, based on the sounds they were exposed to in training and presented with in Novel Nonconforming test items, participants in the AGL experiments only needed to (implicitly) compare the perceptibility of voicing within stops with the same place of articulation or the perceptibility of place of articulation within stops with the same voicing. On the other hand, when relying on Wang & Bilger’s confusion study, it may be necessary to take into account, for example, confusions between [p] and [v] to capture the full picture of the perceptibility of voicing, or between [p] and [d] for the perceptibility of place of articulation. If voicing and place confusions that also involve changes in other features are included, the degree to which stop voicing is more perceptible word-initially vs. word-finally is much diminished, though stop place remains surprisingly more confusable word-initially than word-finally.
Further perceptual studies are needed to determine whether the decrease in perceptibility from word-initial to word-final position really is more severe for stop voicing than stop place of articulation. These investigations might include targeted confusion studies or difficult discrimination tasks like Martin & Peperkamp’s (
I now briefly consider some other possible reasons for the null substantive bias result in Experiments 1 and 2 vs. the positive result in the voicing contrast study, as well as the broader issues those reasons bring to the fore. The first reason is related to the difference between stop place and voicing discussed above but additionally takes language experience into account. That is, what if position has relatively little effect on the perceptibility of stop place of articulation specifically for native English speakers, and this is why Experiments 1 and 2 did not find an effect? Traditional conceptions of substantive bias within Optimality Theory encode the preference for natural phonology in an innate universal constraint set, which contains some constraints but not others, in accordance with universal phonetic facts (
In addition to raw acoustic cues, other factors that might shape the perceptibility of phonological contrasts in a given language could potentially affect the strength of language-specific substantive biases too. For instance, a contrast’s importance for differentiating words in a particular language (i.e. its functional load in that language) may affect its distinctiveness for native speakers (
I do not expect any of these language-dependent factors to ever generate predictions that a phonetically unnatural pattern should be favored over a natural one. It seems unlikely that the functional load of a particular contrast would be significantly greater in a position where, acoustically, it was harder to perceive than in a position where it was easier to perceive precisely because, whatever the reason, phonological systems tend to be phonetically natural. Moreover, even if a contrast’s functional load were to boost its perceptibility in an unexpected position, this would likely not override the influence of raw acoustic cues. With respect to the P-map, universal properties of production and perception will ensure that the general phonetic knowledge it contains is largely the same across languages; what can vary are details like how much the perceptibility of a contrast improves from one position to another.
In sum, universal phonetic precursors have the potential to give rise to substantive biases, which may then play a role in shaping the phonological typology, but the phonetic implementation (of e.g. various contrasts) in specific languages may affect the strength of those biases in native speakers if the phonetic knowledge underpinning them is learned. This may be especially true in adult speakers, who are the most frequent participants in AGL studies. If the perceptibility of major place contrasts in stops is less influenced by position specifically in English, it might explain why Experiments 1 and 2 did not uncover a naturalness bias. This discussion points to the importance of conducting experiments examining the same hypothesized substantive biases in different languages with distinct phonetic implementations. Positive results would show that a substantive bias can become active in learners with access to the right phonetic knowledge, which in turn would mean that that bias could potentially have influenced the phonological typology.
Finally, I will touch on one last possible reason for the difference between the place contrasts and voicing contrast studies, namely, that the explanation is in some way connected to the typology. Half of the initial contrast conditions in Glewwe’s (
I conducted an AGL study that tested for substantive bias in phonotactic learning by examining whether participants exposed to place of articulation contrasts in stops in a given position were more likely to extend those contrasts to a new position where they are more perceptible than to a new position where they are less perceptible. Although the experiments found strong effects of phonotactic learning, participants extended the place contrasts equally in both directions, yielding no support for substantive bias. This lack of an effect might be taken as another entry in the long list of null results that have cast doubt on the substantive bias hypothesis. A closely related study, however, addressed the same question by examining extension of the stop voicing contrast and did uncover an effect of substantive bias, suggesting that it was something specific about stop place of articulation that led to the null finding in this study.
It is possible that the degree to which perceptibility is diminished from word-initial position to word-final position is smaller for stop place of articulation than for stop voicing; preliminary evidence from confusion data supplies some support for this idea. This would reduce the relative unnaturalness of only having place contrasts word-finally, thereby resulting in more symmetrical extension of the place contrasts across positions. The present study reinforces the elusiveness of substantive bias and may support the hypothesis that its role in shaping phonological grammars is subtle. In combination with the voicing contrast study, though, it points to a more nuanced hypothesis: the strength of a substantive bias (or whether it exists at all) varies with the magnitude of its phonetic precursor.
In yielding null substantive bias results while very similar experiments did not, the two experiments reported on here suggest a promising frontier in the further characterization of the nature and scope of substantive bias. Taking the magnitude of phonetic precursors into account may shed new light on existing AGL results and can furnish novel predictions for future experiments. If this line of inquiry proves fruitful, it could eventually help determine which phonetically natural tendencies in the typology might stem in part from substantive bias and which can be attributed entirely to channel bias.
The stimuli are given in a broad IPA transcription (<j> represents [j], <a> represents [ɑ], and <r> represents [ɹ]). Shaded items are familiar (heard in training and test). Bolded items belong to minimal triplets.
An earlier AGL study that also invited participants to extend a phonotactic pattern to a new context is
More precisely, this applies to major place contrasts (labial vs. coronal vs. dorsal) in oral stops. The following discussion refers only to these contrasts. Other contrasts, such as that between retroflex and non-retroflex consonants, have different cues and therefore different patterns of perceptual similarity across positions (see
In conducting his typological study, O’Hara (
To be clear, I assume that substantive bias arises from the phonetic facts that make one phonological pattern more natural than another and not from the typology. Learners may possess implicit phonetic knowledge that could bias them toward some patterns over others, but they do not have implicit knowledge of the typology of the positional distribution of place contrasts in stops.
A reviewer asked whether less successful learning of the Final Contrast language could also manifest as lower acceptance rates of Familiar Conforming or Novel Conforming items (i.e. less willingness to accept test items that fit the trained pattern). While not the focus of this paper, the general implementation of substantive bias that underpins my predictions here assumes there exist markedness constraints penalizing stops with (more) marked places of articulation (e.g. *L
Error bars represent ±1 standard error.
I did not include by-item random slopes for Condition because although the test items were the same in both conditions, they did not fall into the same types in each condition. Thus the Familiar Conforming items in the Initial Contrast and Final Contrast conditions are not exactly the same sets of items, and the same is true for the Novel Conforming items.
Whether acceptance rates were significantly above chance was determined by fitting mixed-effects logistic regressions to the novel items (Novel Conforming and Novel Nonconforming) with the same random effects structure as in the model in
I tested for the substantive bias effect among the non-rule-seeking participants only (14 total; 8 in the Initial condition and 6 in the Final condition). The raw results appear promising: non-rule-seeking participants’ mean acceptance rates of Novel Conforming items were similar (59% in the Initial condition and 61% in the Final condition), but the mean acceptance rate of Novel Nonconforming items was higher in the Final condition (47%) than in the Initial condition (37%). This looks like greater extension of the place contrasts from final position to initial position than vice versa. However, when I fit a mixed-effects logistic regression to the novel items (the same type of model as in
Which test items were Familiar Conforming differed between the two conditions, so removing the Familiar Conforming items meant that the test items were no longer identical in the two conditions in Experiment 2.
This was determined by fitting a mixed-effects logistic regression to the test items (Novel Conforming and Novel Nonconforming) and changing the reference levels of the factors Condition and Conformity so that the model intercept represented the acceptance rate for the relevant combination of Condition and Conformity. When the intercept represented Initial Contrast Novel Conforming items or Final Contrast Novel Conforming items, it was significantly above chance (Initial Contrast:
When the intercept of the model described in fn. 11 represented Initial Contrast Novel Nonconforming items or Final Contrast Novel Nonconforming items, it did not differ significantly from chance (Initial Contrast:
In Experiment 1, like in the place contrasts experiments, the non-stop consonants were voiced sonorants (e.g.
In these experiments, the number of participants in each condition ranged from 29 to 41, which is somewhat higher than in the place contrasts experiments, but the standard errors of the acceptance rates were similar between Glewwe (
White’s experiment also included coronal stops and fricatives [t d θ ð], but I use the labial case to exemplify.
This is echoed by Wang & Bilger’s (
Substantive bias could also be encoded via fixed rankings (or relative weightings) of constraints (see fn. 5).
This is different from Archangeli & Pulleyblank’s (
This research was certified exempt from IRB review by the UCLA Institutional Review Board (IRB#16-001655).
I would like to thank two anonymous reviewers for their thoughtful comments and for helpful suggestions that strengthened the paper. Thanks also to associate editor Juliet Stanton; to Robert Daland, Bruce Hayes, Megha Sundara, and Kie Zuraw; to Charlie O’Hara; and to audiences at the 2017 Annual Meeting on Phonology (AMP 5), the 2018 LSA Annual Meeting, and the UCLA Phonology Seminar. All remaining errors are my own.
The author has no competing interests to declare.