PhD Defense: Zoe Lam

Zoe Lam will have the final oral examination for her PhD thesis on Tuesday, October 9, 2018 at 4:00 PM. The title of her dissertation is Perception of lexical tones by homeland and heritage speakers of Cantonese. The examination will comprise a ~30-minute presentation about the dissertation followed by a question period, first by members of the committee and then opened up to members of the audience.

Please keep in mind that no one will be allowed to enter the room after the examination has begun at 4:00 PM, and that if you must leave before the examination is finished, you will not be allowed to re-enter.

Note: PhD defences are currently *not* being held in the Thea Koerner House due to construction; this defence will be held in Totem Field Studios.


This dissertation compares the lexical tone perception abilities of two populations with different bilingual configurations: Cantonese-dominant adults who grew up in Hong Kong (referred to as homeland speakers), and English-dominant adults who grew up in a Cantonese-speaking household in Canada (heritage speakers). From infancy both were exposed to Cantonese as a first language in terms of chronological order; however, after the onset of schooling, each became dominant in the majority language of their respective society. Given this background, this study investigates whether heritage speakers’ perception of lexical tones of a non-dominant first language (Cantonese) exhibits cross-language effects from a dominant second language (English) that does not have a contrastive dimension of tone. 
A series of perception experiments was conducted using the word identification paradigm. Eight types of audio stimuli were presented to homeland and heritage speakers (N=34 per group), each of which represented a specific configuration of four variables: whether the acoustic signal contained segmental and tonal information, whether the target word was isolated or embedded in a carrier sentence with semantic context, and whether the meaning of the target word was congruous with the carrier sentence. In each trial, participants saw pictures of the target word and minimally contrastive tonal competitors, and were instructed to choose the picture that represented what they heard.
Major findings of this study were: (1) among the eight stimulus types, the accuracy gap between the two groups was the biggest when the stimuli were low-pass-filtered monosyllables with no segmental information or semantic context, which suggests that homeland speakers have a significantly greater ability to distinguish tonally contrastive words by solely relying on tonal information. (2) Both groups showed confusion of overlapping subsets of tone pairs, but heritage speakers had a higher error percentage, which indicates a quantitative but not qualitative difference between the two groups. (3) When the target word was semantically incongruous with the carrier sentence, homeland speakers outperformed heritage speakers by attending to acoustic information, while heritage speakers relied on semantic information relatively more often. In other words, the two groups used different listening strategies in tone identification.