Poster D24, Wednesday, August 21, 2019, 5:15 – 7:00 pm, Restaurant Hall
Parsing trimorphemic words in sentences: Evidence from aphasia
Roberto G. de Almeida1, Maude Brisson-McKenna1;1Concordia University
Introduction: Linguistic productivity is intrinsically dependent on the ability to compute complex hierarchical structures. In morphology, this ability is determined by selectional restrictions of roots and affixes. For instance, in a word such as unstoppable the prefix un- attaches to the complex adjective stoppable not to the verb stop (thus, ruling out *unstop). In the case of unlockable, however, both possibilities exist: [[un][lockable]] “not able to be locked” or [[unlock][able]] “able to be unlocked”. Proper parsing of these trimorphemic structures is thus key to accessing their meaning in natural language use. Few experimental studies have investigated the parsing and interpretation of these types of words in isolation and in sentence contexts (de Almeida & Libben, 2005; Libben, 2003; Libben, 2006; Pollatsek, Stockall, Drieghe, & de Almeida, 2010), with results pointing either to a right-branching or to a left-branching preference, with factors such as context and frequency affecting later, not initial stages of analysis. We investigated morphological parsing in individuals with stroke and aphasia aiming to understand (a) whether there is a default parsing strategy, (b) the potential influence of sentential-semantic context on parsing preferences, and (c) the breakdown of morpho-semantic processing. Method: Participants were 14 individuals with stroke, 12 of whom were diagnosed with aphasia (3 fluent [FL], 2 mixed [MX], 2 mixed but predominantly non-fluent [MN], 5 non-fluent [NF]) and 2 were RH-damaged. Controls were 30 healthy individuals matched to the clinical groups in age, sex, education. They were all native speakers of English. Stimuli were 48 sentences containing ambiguous trimorphemic words (e.g., unlockable), with 24 biasing towards the left-branching, 24 towards the right-branching analysis of the trimorphemic word (e.g., ‘When the zookeeper went to unlock/lock the cage, he found it was unlockable’). In addition, materials included 24 sentences containing left-branching words ([[refill][able]]) and 24 sentences containing right-branching words ([[un]stoppable]). These sentences were divided into two booklets, with each participant completing one booklet. Participants rated each sentence on a 5-point scale (Rating task) and then were asked to indicate, by drawing a line on a target word, where in the word they thought a separation could be made (Parsing task). Results and Discussion: Analyses by items (Mycroft et al., 2002) were based on deviations from the control group. With the exception of NF, all groups, showed strong preference for right branching. Of note were the NF and MX groups which showed greater deviations in parsing strategies (F (1, 11) = 5.43, p = .04, ηp2 = .56), with NF showing a significant left-branching preference for all word types, irrespective of meaning, even with unambiguous right-branching words (thus yielding *[[unthink]-[able]]). MX showed the reverse pattern, with a significant preference for prefix-stripping (right-branching, thus yielding *[[re]-[fillable]]). Results are compatible with online studies (de Almeida & Libben, 2005; Pollatsek et al., 2010) suggesting that both parses are available during initial stages of analysis, regardless of context. But results also show that NF and MX aphasia groups are the least sensitive to morpho-semantic restrictions, applying default parsing strategies leading to semantic anomalies.
Themes: Disorders: Acquired, Morphology
Method: Behavioral