Psycholinguistic mechanisms of classifier processing in sign language

Abstract

Nonsigners viewing sign language are sometimes able to guess the meaning of signs by relying on the overt connection between form and meaning, or iconicity (cf. Ortega, Özyürek, & Peeters, 2020; Strickland et al., 2015). One word class in sign languages that appears to be highly iconic is classifiers: verb-like signs that can refer to location change or handling. Classifier use and meaning are governed by linguistic rules, yet in comparison with lexical verb signs, classifiers are highly variable in their morpho-phonology (variety of potential handshapes and motion direction within the sign). These open-class linguistic items in sign languages prompt a question about the mechanisms of their processing: Are they part of a gestural-semiotic system (processed like the gestures of nonsigners), or are they processed as linguistic verbs? To examine the psychological mechanisms of classifier comprehension, we recorded the electroencephalogram (EEG) activity of signers who watched videos of signed sentences with classifiers. We manipulated the sentence word order of the stimuli (subject-object-verb [SOV] vs. object-subject-verb [OSV]), contrasting the two conditions, which, according to different processing hypotheses, should incur increased processing costs for OSV orders. As previously reported for lexical signs, we observed an N400 effect for OSV compared with SOV, reflecting increased cognitive load for linguistic processing. These findings support the hypothesis that classifiers are a linguistic part of speech in sign language, extending the current understanding of processing mechanisms at the interface of linguistic form and meaning. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Figure 1.

Example representing the two experimental conditions: Both arguments were referenced in space by a classifier handshape (in this case the two referents are placed in space in a way indicating that they are standing opposite each other with more distance between them). Then, either the hand representing the first referent (signer’s left hand in SOV orders) or the second referent (signer’s right hand in OSV orders) started to move; i.e. indicating the active referent. The sentence shown means: “Two girls stand opposite each other and one of them (either the one on the left or the one on the right side) jumps towards the other.” Signs are glossed with capital letters

Figure 2.

Top: Comparison of SOV vs. OSV conditions with regard to the time point when the classifier predicate started its movement. The vertical line represents the time point at which the first frame when the hand referencing the subject starts to move was visible. Negativity is plotted upwards. The red square marks the time window in which the effect of ORDER became significant (300–800 ms time window). Bottom: The topographic plots illustrate the corresponding voltage difference between the two conditions over the epoch of interest, i.e. from 300 and 800 ms showing the broad scalp distribution of the N400 effect.