SPEECH ERROR ANALYSIS FROM HINDI
3.7 Phonological markedness
All patients are more likely to simplify rather than complicate syllabic structure.
However, is this also the case at the segmental level? In other words, does segment complexity (or markedness) play a role in which phonemes are deleted, substituted or inserted? In phonological terms unmarked phonemes are those that are more frequent, natural and simpler to articulate than marked phonemes. For example, Hindi distinguishes between voiced and unvoiced stops such as /k/ and /g/. These two phonemes are identical except for the additional property (or mark) in the latter that makes it voiced. Within voiced segments there is another difference in aspiration such as /k/ and /kh/ which are again differentiated by the additional property of aspiration /_h/. Markedness can have overlapping dimensions in that a phoneme can be viewed in different terms based on its features. For Hindi, these dimensions were defined into place, manner and two laryngeal features: voicing and aspiration.
Place was divided into three broad categories with the following values of markedness: velar, labial and coronal. Coronal and labial were treated as equally simple, as there is mixed evidence as to which category is more complex, while velar consonants were treated as the most marked (De Lacy, 2006). Manner was categorised with stops being the simplest followed by affricates, fricatives and then all other manner categories. Voiced and aspirated consonants were considered to be more complex than unvoiced and unaspirated consonants. The tables below show the organisation of errors based on place, manner and laryngeal features. The rows in Table 20 and Table 21 are arranged in ascending order of markedness.
99 Table 20 Percentage of Errors for Place in Hindi
Increase expected ↓ Decrease expected ↑
Deletion Target Substitution Insertion Response Substitution
Coronal 2.5% 10.5% 0.7% 9.6%
Labial 0.8% 4.8% 1.2% 6.2%
Velar 2.9% 9.2% 1.2% 8.4%
Table 21 Percentage of Errors for Manner in Hindi
Increase expected ↓ Decrease expected ↑
Deletion Target Substitution Insertion Response Substitution
Stop 1.0% 8.7% 1.0% 8.1%
Affricate 1.3% 9.4% 0.7% 17.4%
Fricative 8.3% 28.4% 0.8% 28.0%
Nasal 1.2% 5.4% 0.3% 2.9%
Liquid 4.8% 4.3% 1.4% 4.5%
The patterns are not clear and do not follow as expected. The trend is clearer in Table 22 where voicing and aspiration are considered. Deletions do not follow the expected pattern but all of the other errors do.
Table 22 Number of Errors for Voicing and Aspiration in Hindi
Deletion ↓ Target Substitution ↓ Insertion ↑ Response Substitution ↑
Unvoiced Unaspirated 3.3% 10.5% 1.3% 15.3%
Aspirated 0.3% 32.2% 0.0% 2.3%
Voiced Unaspirated 3.0% 4.9% 0.9% 5.3%
Aspirated 0.7% 29.1% 0.0% 2.6%
The above tables divide the errors according to the place, manner and laryngeal categories. The categories are in ascending order according to markedness. The less marked
100 phonemes should be less likely to be deleted or substituted in the target, but more likely to be inserted or replace a substituted phoneme in the response. The contrary should be true for more marked phonemes. However, the data is ambiguous for place (Table 20) and manner (Table 21). On the other hand, voicing and aspiration (Table 22) conform to this pattern. This is very likely to be due to the fact that place and manner are multi-feature properties with features with different levels of markedness combined to produce a segment property. For example, the phoneme /t / is a coronal affricate. It would be categorised as more marked in terms of manner and less marked in terms of place. Similarly, /k/ is a velar stop meaning that it is less marked for manner but more marked for place.
However, voice and aspiration are the result of single feature changes: [±voice] and [±sg]. This provides a clear pattern not seen in the other two categories. To see the overall markedness changes, we looked at the overall markedness change in substitution errors. We looked at place, manner, voicing and aspiration and produced an overall complexity change (less marked, more marked or neutral) depending on the average change in markedness.
Table 23 General Characteristics of Segment Errors in Hindi
Segmental Errors Difference between
Less and more
HK, MJ and PK show a clear trend towards unmarked phonemes in their errors while AS and NC do not. NC has an equal proportion of simplifications and complications. AS does have more phonemes that are less marked, but there is no significant difference between the two categories. The effect is not always consistent because other factors such as syllable
101 position, structure integrity and phonotactic legality may also be a factor in the ultimate output. The conclusion of this analysis would be that while markedness may play a role in errors, only single feature analyses could provide a clear pattern, while multi-feature properties may be too diluted to provide distinct trends.
3.8 General discussion
This chapter provided the results from a study conducted in Delhi, India with the participation of 5 native Hindi speaking stroke survivors. While 11 patients were recruited, these 5 were selected based on their suitability for the purpose of this study. They were assessed with tests that were equivalent to certain PALPA tasks. This initial assessment showed that the patients had very little problems in word comprehension or auditory discrimination. They also had no difficulties with lexical decision tasks. Some patients had difficulties with nonword minimal pairs.
The experiments consisted of reading, repetition and picture naming tasks based on stimuli prepared to assess various syllable structures and clusters found in Hindi. The patients made more nonword errors than word errors. Among word errors, all of the patients except AS made very few formal and semantic errors. AS, on the other hand, made a larger number of formal errors. However, these did not make him deviate from the other patients in his rate of nonword errors (also see Dell et al., 2006). Nonword errors were classified as individual, sequence and multiple errors. Multiple errors involved more than three nonadjacent segments and were removed from further analysis. Sequence errors involved two or more adjacent segments while individual errors were single segment errors. Binomial regression analysis showed that all of the patients showed a consistent main effect of length, meaning that the number of segments played a significant role in the probability of an error occurring.
We then defined the licensing principle of syllable structure hierarchies upon which we based further analysis. If syllable structure is stored within the lexicon, there should be
102 asymmetry in the distribution of errors between primary licensers and other syllable position.
In terms of addressing the issue of syllable structure preservation, we looked at errors among consonants versus vowels, syllable positions and syllable boundaries. All patients (except AS) had significantly more consonant substitutions as opposed to vowel substitutions. All patients deleted consonants more often than vowels. Consonant-to-vowel substitutions or vice versa were not found in the errors. Substitution errors are the most common type of error in all the patients as they have the potential to optimise sonority. Substituting vowels with consonants would require the insertion of a new vowel to license the rest of the consonants in the syllable. Substituting consonants with vowels would result in a new syllable being built around it. Both of these scenarios require considerable reorganisation of the syllable structures within a word. These observations underline the idea that vowels are the primary licensers for the syllable hierarchy. Moving from the primary licenser at the highest level to secondary licensers (core positions), we find similar results. Deletions of target satellite positions occur more often when compared with core positions for both onset and coda.
Deletion errors would be considered to modify syllable structure in all instances. However, deletions affecting satellite positions result in no modifications to syllable structure as opposed to core positions which are most likely preserved by stronger levels of activation during production. This data is also supported by Den Ouden (2002) and Stemberger and Treiman (1986) who found more errors in the syllabically weak positions of complex onsets than for stronger core positions. However, the Hindi data does not show similar patterns for substitution errors. In these errors, core positions are just as likely as or more likely to be substituted than satellite positions. This data can be explained by the fact that substitutions of core positions do not result in the movement of any segments (such as those in satellite position). Therefore, there is no reorganisation of segments or structure in these errors. This means that the greater vulnerability of core positions to substitution does not refute the data
103 from deletions. The primacy of vowels and the vulnerability of satellite positions indicate that syllables (if stored within the lexicon) are organised hierarchically.
Another interesting aspect of the errors was at syllable boundaries. Heterosyllabic cluster, homosyllabic cluster and geminate errors showed a tendency to keep the structure intact. Heterosyllabic clusters are the clearest evidence for this trend as they tend to retain their heterosyllabic structure or turn into geminates. They never changed into homosyllabic clusters. This trend is similar to a single case study by Romani and Calabrese (1996) which found that heterosyllabic clusters replaced geminates in the errors of an apraxic patient.
Geminates often turn into heterosyllabic clusters and vice versa in the Hindi errors as well.
Homosyllabic cluster errors are more ambiguous as their numbers were much lower than other errors. This is most likely because patients tended to simplify clusters with vowel insertions.
Finally, syllable position constraints are not to be confused with position specific phonemes. It is clear that phonemes move between different syllable position not only in pure movement errors but also in some substitution errors. This indicates that phonemes are linked to abstract structures rather than being pre-specified for different syllable positions (as in the Dell model).
Romani et al., (2011) provided results from Italian that were similar (but not identical) to what we have seen in this chapter. The results from this chapter suggest that Hindi may have a lexicon which specifies an abstract syllable structure to organise phonemes.
While the role of syllable structure has been used to explain articulatory production and stress assignment, the evidence from Italian and Hindi illustrate that it also has a role to play in organising phonemes. The fact that typologically different languages like Italian and Hindi preserve syllable structure indicates that this may be a universal phenomenon for all languages. This chapter provided evidence to that effect in showing that errors that are likely
104 to involve complicated transformation (such as heterosyllabic clusters becoming homosyllabic) tend to be avoided. This is most likely due to those kinds of alterations being computationally expensive. They also violate constraints to keep the output as similar to the input as possible (see chapter 6 for explanation on faithfulness constraints in Optimality Theory).
3.9 Conclusion
This chapter has presented evidence from Hindi that supports the idea that syllable structure may have lexical representation. The results show preservation of syllabified representations may be cross-linguistic in that the effects are seen in Hindi as well as in Italian (Romani et al., 2011). However, it could be argued that this effect is not universal but isolated to certain languages with particular constraints, syllable typology or resyllabification rates. Chapter 2 showed us that Italian and Hindi have a much lower resyllabification rate than English. As models such as LRM (Levelt et al., 1999) put forth resyllabification as a justification for exclusively post-lexical syllabification, it could be argued that languages with lower rates of resyllabification are more likely to represent syllable structure within the lexicon while those with higher rates (whatever the demarcation for ‘high’ would be) organise phonemes differently. Such a situation is probable but highly unlikely in that it is difficult to imagine the lexicons between human beings being organised differently in such a central aspect of their configuration. However, the only way to test this hypothesis is to look at the error patterns in a language with higher rates of resyllabification: English.
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