Amodal aspects of linguistic design

Abstract

All spoken languages encode syllables and constrain their internal structure. But whether these restrictions concern the design of the language system, broadly, or speech, specifically, remains unknown. To address this question, here, we gauge the structure of signed syllables in American Sign Language (ASL). Like spoken languages, signed syllables must exhibit a single sonority/energy peak (i.e., movement). Four experiments examine whether this restriction is enforced by signers and nonsigners. We first show that Deaf ASL signers selectively apply sonority restrictions to syllables (but not morphemes) in novel ASL signs. We next examine whether this principle might further shape the representation of signed syllables by nonsigners. Absent any experience with ASL, nonsigners used movement to define syllable-like units. Moreover, the restriction on syllable structure constrained the capacity of nonsigners to learn from experience. Given brief practice that implicitly paired syllables with sonority peaks (i.e., movement)--a natural phonological constraint attested in every human language--nonsigners rapidly learned to selectively rely on movement to define syllables and they also learned to partly ignore it in the identification of morpheme-like units. Remarkably, nonsigners failed to learn an unnatural rule that defines syllables by handshape, suggesting they were unable to ignore movement in identifying syllables. These findings indicate that signed and spoken syllables are subject to a shared phonological restriction that constrains phonological learning in a new modality. These conclusions suggest the design of the phonological system is partly amodal.

Figure 1. Syllables and morphemes across modalities.

Panel a illustrates the pattern of meaningful elements (morphemes) and meaningless elements (syllables) in an English word. Panels b-c illustrate the manipulation of syllable and morpheme structure in English words (b) and ASL signs (c). Note that one-syllable signs have a single movement, whereas two-syllable signs have two movements (marked by arrows). Morphemes, by contrast, are defined by the number of handshapes. For example, the monomorphemic monosyllabic sign MARRY has a single group of active fingers (the open hand with the thumb extended) whereas in the monosyllabic bimorphemic sign MIND-FREEZE there are two groups of active fingers, the “one” (an extended index finger) handshape changes to an open hand with the thumb extended.

Figure 2. The distinction between syllables and morphemes in the novel ASL stimlus items.

Note that one-syllable signs have a single movement, whereas two-syllable signs have two movements (marked by arrows). Morphemes, by contrast, are defined by the number of handshapes. For example, the monomorphemic monosyllabic sign has one group of active fingers (the closed fist with the thumb positioned infront of the fingers, the “S” handshape in ASL) whereas in the monosyllabic bimorphemic sign, there are two groups of active fingers - the “S” handshape changes to an “F” handshape (the tip of the pointer finger touching the tip of the thumb to form a small circle with the other three fingers extended).

Figure 3. The proportion of “one” responses given by Deaf signers in Experiment 1 for the syllable count task (a), morpheme count task(b), and the incongruent trials taken from both tasks (c).

Error bars are confidence intervals, constructed for the difference between the means.

Figure 4. The proportion of “one” responses given by nonsigners in Experiment 2 (without feedback) for the syllable count task(a), morpheme count task (b), and the incongruent trials taken from both tasks (c).

Error bars are confidence intervals, constructed for the difference between the means.

Figure 5. The proprtion of “one” responses given by nonsigners in Experiment 3 (with feedback consistent with the natural phonological association of syllables and movement) for the syllable count task (a), morpheme count task (b), and the incongruent trials taken from both tasks (c).

Error bars are confidence intervals, constructed for the difference between the means.

Figure 6. The proportion of “one” responses given by nonsigners in Experiment 4 (with feedback suggesting an unnatural phonological association of syllables and handshape) for the syllable count task (a), morpheme count task (b), and the incongruent trials taken from both tasks (c).

To clarify the effect of learning from feedback, we indicate the expected responses, color-coded by task. Specifically, syllable count responses (in red) should depend on the number of handshapes; morpheme count (in blue) should depend on the number of movements. Error bars are confidence intervals, constructed for the difference between the means.