Liddell’s mental space model explains many gestural phenomena within sign languages; evidence from neurolinguistic and psycholinguistic studies support his analysis (e.g., Corina, 1999; Emmorey, 1999, 2002). However, there is also evidence suggesting that the use of space must be in some ways categorical and therefore linguistic (Aronoff, Meir, & Sandler, 2000; Meier, 2002; Rathmann & Mathur, 2002). Meier in particular notes that there are restrictions on pointing (i.e., the extent to which different forms can point and how they point) which suggest that indexing must be linguistically determined.
Rather than seeking answers from the way language is acquired or processed, here I explore phonetic properties of signs themselves as they are used within the signing space. This study compares singular and plural forms in terms of the extent to which they “point to” their referents (indexicality). Some signs are clearly indexic, such as the singular pronoun (simply a pointing sign) as well as classifiers, which are signs that denote particular characteristics of referents. These pronoun and classifier forms (indexers) are found in all sign languages we know about today. Certain classes of verbs (also found in all known sign languages) are also indexic.
While the majority of pronouns and classifiers tend to be indexic, not all of them are. Some signs are not so indexic, such as the first person plural pronoun WE in ASL, shown in Figure 1. This pronoun consists of two points at the center of the signer’s chest; it does not point to all its referents or really to any of its referents other than the signer. However, the ASL sign WE used to be more indexic than it is today (Klima & Bellugi, 1979). This sign previously consisted of a series of pointing signs, starting and ending with a point to self. Thus we see a loss of indexicality over time. The series of pointing signs in the older form used the signing space, but the current form does not.
Figure 1: WE
Loss of indexicality can also occur synchronically, for example with singulars versus plural verbs. The so-called exhaustive (i.e., distributive plural) verb that occurs in ASL and other sign languages is rhythmically distinct from and is reduced in form compared to three or more predicates. This reduction in form makes the exhaustive form less indexic than three separate predicates (see Cormier, 2002 for examples and more details).
In order to account for such loss of indexicality, I compared the phonetic forms of singular and plurals using two studies. In the first study, the indexicality of plural pronouns was investigated. The results revealed an exclusive form of the plural pronoun WE in ASL – i.e., a form of the pronoun that excludes some salient referent in the discourse. This exclusive variant can be displaced to the signer’s right side or left side (cf. the neutral form WE in Figure 1 and the exclusive form in Figure 2). Interestingly, each signer participating in the study consistently showed a general preference for either the right or left side, regardless of where the referents were established in the signing space. For example, if a signer were using an exclusive form to refer to herself and a group of people on her left (excluding some salient referent in the discourse), that signer would use a form displaced to either her left or her right side. Thus the exclusive form of WE in ASL can be indexic but it need not be. It seems that what is most important for marking exclusivity is the displacement, so much so that the indexicality of the pronoun may be compromised.
Figure 2: WE-exclusive
In order to get an overall picture of indexicality for these pronouns, I took a more general measure of indexicality (lateral indexicality) based on which side of the midline the pronoun was produced. If the pronoun was produced on the same side of the signer’s midline as the referents, the pronoun was considered laterally indexic. Otherwise, the pronoun was considered laterally non-indexic.
Results showed that pronouns referring to many referents were less laterally indexic than pronouns referring to two or three referents. This suggests that a greater number of referents leads to a loss of indexicality.
These results are important because of how they relate to the second study, an instrumental study comparing the indexicality of singular indexers and verbs with plural indexers and verbs. This study used a motion analysis system to measure distances between verbs and indexers (see Cormier, 2002 for more details).
For example, Figures 3 and 4 show a signer describing a film clip in which a woman gives a man a piece of paper. First the signer used a person classifier to set up a location for the woman, as shown in Figure 3. She then produced the verb GIVE to show that the woman gave the paper to the man; the starting position of the verb is shown in Figure 4. Measurements were taken of the classifier (indexer) location shown in Figure 3, and also the verb location shown in Figure 4. The distance between these two locations was then calculated. Similar distances were obtained for one, two and three referents.
Figure 3: Classifier for standing person (CL-1)
Figure 4: Start of path movement for verb GIVE
Statistical analyses showed that the mean distance between singular verbs and their indexers (i.e., for one referent) was significantly smaller than the mean distances for 2, 3 and many referents (p<0.0003). Thus, the significant contrast found was for one referent vs. more than one referent. This suggests that singulars do indeed more precisely indicate their referents than plurals do.
In addition to the instrumental analysis, lateral indexicality was also determined, this time based on comparisons of the indexer and verb rather than the pronoun and its referents. Thus, if the verb was produced on the same side of the signer’s midline as the indexer, the verb/indexer pair was considered to be laterally indexic. Otherwise, the verb/indexer pair was considered to be laterally non-indexic. Interestingly the same pattern emerged with this study as with the pronoun study – i.e., a gradual decrease in lateral indexicality as the number of referents increases.
These results suggest that plurals (including duals and trials) are indeed less precise than singulars. Some of the results could be attributed to cognitive or motoric factors – that is, it might be easier to keep track of one referent than many referents. However, lateral indexicality results suggest the significant difference between singulars and non-singulars cannot be due entirely to motoric or cognitive factors, since it should not be physically or cognitively difficult to match left-side located signs with left-side located referents and right-side located signs with right-side located referents. Overall the results from both studies provide phonetic evidence that plural marking affects indexicality in ASL by causing a reduction in form.
Previous studies by Liddell and others who subscribe to his gestural model have only ever taken into account ways in which signers index a single referent. Plural forms have been largely ignored in the research on indexing, and yet these forms are key to understanding the way in which gesture (i.e. indexing) overlaps with grammaticized, linguistic information (i.e. number marking).
As noted above, proponents of the linguistic status of indexing argue that the restrictions on indexing suggest it cannot be purely gestural. Meier (2002) notes that “although the form of agreement may be gestural, the integration of these gestural elements into verbs is linguistically determined.” I’d like to take this a step further and claim that the integration of gestural elements (e.g. the use of space for indexing) with morphological marking (e.g. number marking) is linguistically determined. The fact that indexers and verbs are less indexic when morphologically inflected for plural suggests that the use of space with these forms is in some sense less intuitively gestural than we might expect given how people normally use gestures for communication.