Rules: Do they really rule?
The phonological generativity with which babies create utterances in their language hasamazed thinkers for centuries [1, 2]. For speech processing, which requires that hierarchical dependencies and bindings be extracted from linear signals , Berent  argues phonological productivity is constrained not by naturalness concerns but rather by symbolic algorithms specified over algebraic variables organized into equivalence classes (e.g. IDENTITY: *C1__C2; C1, C2, C3…Cn ε [C]). Language specific applications of each rule draw on values derived from phonological inventories. Such computational representational accounts of cognition [e.g, 5, 6] differ from naturalness accounts in making categorical demands on phonological rule outputs.
To test this account, we conducted two Forced-Choice experiments with 15 native Malayalam speakers, addressing single-melody velar gemination after preceding vowels [i, e, a] [7, 8]. Two palatalizing suffixes ([k:uka], [k:ə]) figured in the first experiment, an additional non-palatalizing suffix ([kal]) in the second. A male native speaker recorded [i, e, a]-final nonce-stems conjugated with the suffixes, in both palatalized and unpalatalized forms. Participants listened to matched pairs of palatalized and unpalatalized forms (15 repetitions per vowel per suffix), and indicated their preference using a keyboard. An algebraic computational phonology should impose palatalization across the board with licensed suffixes [k:uka] and [k:ə], and avoid it entirely with unlicensed [kal]. A natural phonology, however, should obey the phonetic implicational laws  without exception. Co-articulatory (phonetic) and grammatical accounts of the process can also be contrasted, in that highly unnatural [a]_[kkə] contexts create grammatical demands to trigger palatalization, while more natural [i, e]_[kal] environments would block it. This is because, typologically, palatalization after front vowels [i, e] is prevalent, unlike after [a] .
In experiment 1 (Figure 1) we found a significant vowel effect, F(1, 14) = 20.01, p < .01, but no suffix effect or interaction. In planned contrasts, [i, e] induced more triggering than [a], p < .05. Experiment 2 (Figure 2) showed main effects of vowel, F(1, 14) = 24.13, p < .01, and suffix, F(1, 14) = 917.72, p < .01, with a vowel*suffix interaction, F(1, 14) = 7.09, p = .01. Planned contrasts again found [i, e] more effective than [a], p < .01, and no significant difference between [i, e]. Thus, identical performance was found for the two licensed suffixes in each experiment, pinning the source of the interaction in Experiment 2 to unlicensed [kal], for which only sparse accidental palatalization occurred with all vowels. Our results thus conform overall to the licensing pattern for suffixes described by Mohanan . More importantly, however, our data show that a phonological mind can generalize rules to novel forms against naturalness concerns [also 11,12]. Such generativity is attainable only through algebraic mechanisms operating on equivalence classes [13,14]. Further, while our data fail to display any bias for the phonetic laws, the lack of bias is not absolute ([i, e] > [a]).
We interpret this as reflecting the double duty of the sound domain: ensuring infinite productivity from finite contrasts (core phonological grammar), while optimizing phonetic plausibility to attain efficient transmission (articulatory and perceptual interfaces with the sensory-motor system). Our results display the interaction between an equivalence class of trigger vowels ([i, e, a]) all members of which undergo an algebraic rule and create palatalized forms with licensed suffixes ([k:uka, k:ə]), but not with the unlicensed [kal]. Such computations in phonology may, however, be sensitive to functional phonetic concerns (consider the 28% lapse in palatalized preference with [a]), though such concerns are readily ignored if they conflict with the grammar [15, 16] (consider the unrestrained violation of all naturalness concerns we found with the unlicensed suffix [kal]). In the context of language and its externalization, viewed as computation by a digital system with subsequent transmission through an analog sensory-motor system, we conclude that phonological processing manifests algebraic operations that are purely algebraic, but whore serial/linear externalization involves functional optimisation of the output of phonological computations.
1. Darwin, C. (1888). The descent of man, and selection in relation to sex (Vol. 1). Murray
2. Chomsky, N. (1959). On certain formal properties of grammars. Information and Control, 2(2), 137–167.
3. Cutler, A., Eisner, F., McQueen, J. M., & Norris, D. (2010). How abstract phonemic categories are necessaryfor coping with speaker-related variation. Laboratory Phonology, 10, 91–111.
4. Berent, I., Everett, D. L., & Shimron, J. (2001). Do phonological representations specify variables? Evidence from the Obligatory Contour Principle. Cognitive Psychology, 42(1), 1–60.
5. Fodor, J. A., & Pylyshyn, Z. W. (1988). Connectionism and cognitive architecture: A critical analysis. Cognition, 28(1), 3–71.
6. Chomsky, N. (2009). Cartesian linguistics: A chapter in the history of rationalist thought. Cambridge University Press.
7. Mohanan, K. P. (1982). Lexical phonology.
8. Mohanan, K. P., & Mohanan, T. (1984). Lexical phonology of the consonant system in Malayalam. Linguistic Inquiry, 575–602.
9. Wilson, C. (2006). Learning Phonology With Substantive Bias: An Experimental and Computational Study of Velar Palatalization. Cognitive Science, 30(5), 945–982. http://doi.org/10.1207/s15516709cog0000_89
10. Maddieson, I., & Disner, S. F. (1984). Patterns of sounds.
11. Berent, I., Steriade, D., Lennertz, T., & Vaknin, V. (2007). What we know about what we have never heard: Evidence from perceptual illusions. Cognition, 104(3), 591–630.
12. Berent, I., Balaban, E., Lennertz, T., & Vaknin-Nusbaum, V. (2010). Phonological universals constrain the processing of nonspeech stimuli. Journal of Experimental Psychology: General, 139(3), 418
13. Berent, I. (2013). The phonological mind. Cambridge: Cambridge university press.