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    Isolation and characterization of potential PHB-degrading microorganisms from a Southern Ontario landfill
    (University of Waterloo, 2026-08-13) Thomas, Madison
    Plastic is essential to day-to-day life. Most plastics create large amounts of waste and emit greenhouse gasses at every life cycle stage from production to degradation, which can have harmful impacts on the environment and cause permanent damage to ecosystems. Polyhydroxybutyrate (PHB) is a proposed ecofriendly alternative to petroleum-based plastics with promising applications as a plastic packaging alternative. It is expected that PHB plastics will be disposed of similarly to petroleum plastics, and thus with increased production and use, the amount of PHB plastic waste in landfills will increase. This research explored the ability of landfill-derived microorganisms to biodegrade PHB through culture-based and genomic methods. The objectives of this research were to confirm the function of and identify PHB-degrading microorganisms from the landfill and to identify and explore their PHB degradation mechanisms. Landfill leachate was spread on PHB-containing selective plates to identify PHB-degrading colonies. From this, colonies were isolated confirming the presence of microorganisms capable of degrading PHB. Isolates from this assay were sequenced using Nanopore MinION sequencing and genomes were assembled using a long-read consensus assembler, autocycler, and annotated using bakta, creating high-quality long-read genome assemblies. Isolates were then taxonomically classified using GTDB-tk and genus/family trees created using GtoTree. Streptomyces, a genus containing many PHB-degrading species, was the most frequently isolated genus. Other taxa isolated include members of the genera Comamonas, Afipia, and Pseudomonas as well as a member of the family Micrococcaceae. All these lineages already contain known and predicted PHB degrading species. Two isolates from genera with no currently described PHB degrading species, Rahnella and Leifsonia, were cultured. Following gene annotation, the majority of isolates’ genomes encoded a likely PHB depolymerase. The Comamonas isolates’ genomes encoded both extracellular and intracellular depolymerases. Four isolates, the three Comamonas and the Afipia, had the full pathways for PHB degradation and synthesis encoded on their genomes. The Pseudomonas isolate genome encoded potential proteins for most of the PHB degradation and synthesis pathways, however, it appears to encode an intracellular medium chain length PHA depolymerase, and no PHB depolymerases were identified in this genome. The Leifsonia, Micrococcaceae, and Rahnella isolates’ genomes encoded probable Blastp predicted PHA depolymerases. The Rahnella isolate’s genome encoded a Bakta predicted PHB depolymerase. For all four, no matches to PHB depolymerases were found in the NCBI protein database. These isolates may have novel, more divergent PHB depolymerases or novel PHB degrading mechanisms, representing potential new pathways and enzymes for biotechnologists looking to industrialize PHB production and degradation. This work identifies microorganisms from landfill communities that can degrade PHB. This indicates that there is the potential for this process to occur in landfills and identifies the members of the microbial community that may be involved. The identification and analysis of the isolates expand the known diversity of PHB-degrading microorganisms, while identifying both known PHB degrading mechanisms and new areas of uncertainty for further research.
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    Teaching Toonies: A User-Centric Approach to Designing a Robot Companion for Language and Cultural Learning
    (University of Waterloo, 2026-08-13) Fernandes, Neil
    Newcomer children face compounding challenges upon resettlement: acquiring a new language, adapting to unfamiliar social routines, and cultivating community belonging. Consequently, language and culture are deeply interconnected processes. In the context of this thesis, I focus more on English language acquisition and Canadian cultural familiarization for Newcomer children who have come to Canada. While community-based literacy programs offer vital, low-stakes environments to support this socio-cultural orientation, tutors often struggle to balance language instruction, emotional support, and attention management for highly diverse groups within limited resource constraints. SARs present an opportunity to facilitate and encourage language practice without replacing human educators. This thesis investigates the user-centered design and evaluation of Maple, a peer-like social robot engineered as a tutor-mediated companion for young newcomer children (ages between 5 to 7). Grounded in language socialization and social learning theories, along with the Design Thinking design philosophy, Maple helps children rehearse situated interactions and everyday routines, actively mitigating the anxiety and fear of evaluation often associated with additional-language acquisition. Utilizing an iterative, co-design framework, this research engaged literacy experts and HRI researchers through shadowing, interviews, and an RTA to establish critical SAR design requirements. The resulting prototype delivers story-based learning via a multi-modal "visual novel" interface featuring embedded formative assessments. To foster inclusivity and prevent cultural bias, the narrative employs anthropomorphic Canadian animal characters, grounding vocabulary in local contexts without imposing a singular human demographic. A mixed-methods user study with expert tutors evaluated Maple's pedagogical fit, usability, and classroom orchestration. Results show tutors perceived Maple as highly engaging and effective at lowering the social risk of language practice. Operating within a triadic learning architecture (tutor-child-robot), Maple is designed to function as a "second voice" for repetitive practice. However, findings also emphasize that the robot's physical embodiment and active behaviors must be carefully bounded to prevent extraneous cognitive load and classroom disruption. This thesis argues that the utility of SAR like Maple does not lie in the automation of instruction. Rather, its value lies in providing brief, playful, and socially secure moments of practice that enhance learner participation while safeguarding the human tutor’s central role in pedagogical guidance, cultural translation, and socio-emotional care.
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    Putting the Brakes on Slot Machine Gambling: Reducing Problematic Gambling Engagement Through Strategic Applications of Friction
    (University of Waterloo, 2026-08-13) Oliveira, Jacob
    Slot machines are designed to promote continuous, automatic engagement, often producing a state of deep absorption known as dark flow. The present research examined whether introducing brief in-game friction, implemented as short mandatory pre-spin delays, would be associated with reductions in gambling perseverance and the experience of dark flow. Across two experiments using a simulated slot machine, participants were assigned to either a Friction condition, in which brief lockout delays preceded spins, or a Non-Friction condition with uninterrupted play. Experiment 1 assessed behavioral perseverance as time spent gambling during a voluntary free-play period following mandatory play, along with post-play measures of flow, positive affect, and negative affect. Experiment 2 examined subjective experience during play using real-time in-task thought probes, in addition to retrospective measures. Results indicated that friction was associated with reduced time spent gambling and greater awareness of time passing, while no reliable differences emerged in self-reported flow, enjoyment, or affect across either experiment. These findings suggest that brief, design-level interruptions may reduce gambling persistence while largely preserving subjective engagement, highlighting friction as a potentially scalable harm-reduction strategy.
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    An Exploration of Parent-Child Joint Attention During a Problem-Solving Task: A Novel Eye Tracking Method
    (University of Waterloo, 2026-08-13) Mahenthiran, Thuvaraka
    Parents play a critical role in helping their young children navigate challenging or novel problems (Ladd & Petit, 2002). Studies show that joint attention (JA) is a key predictor of successful collaboration, which contributes to successful problem solving and learning (Barron, 2003). JA occurs when two individuals coordinate their focus to mutually share attention towards a common event or object (Bradley et al., 2023). Most studies examine JA between infants or toddlers and a parent without considering other aspects of the interaction (e.g., Ambrose et al., 2020; Guo & Feng, 2013). Consequently, there is limited work on how JA relates to parenting behaviours in naturalistic learning contexts. This thesis examines whether the proportion and type (child-led or parent-led) of JA differ depending on the parents’ motivational state and whether parental behaviours are associated with JA. I examined eye tracking data from a subset of participants in a larger study (N=29 dyads; child ages 4.00 - 5.83 years) in which parents’ and children’s eye movements were recorded while children completed three challenging tangram puzzles (modeled after Lunkenheimer et al., 2017). The dyads were randomly assigned to one of two study conditions used to manipulate the parents’ motivational states: process-oriented or outcome-oriented. JA frequency and type (child vs. parent led) were coded for predefined regions of interest (e.g., the puzzle boards, parent hand, etc.). Proportion and type of JA was unrelated to motivational state; however, regardless of condition children primarily drove JA during this task. By exploring the dyadic association between parents and their children in a naturalistic task, research like this can inform parents and early childhood educators about how to best support children’s problem solving.
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    When does the chance of getting caught matter? Apprehension probability and its impact on punishment judgments
    (University of Waterloo, 2026-08-13) Kim, Jisoo
    Punishment is intended not only to respond to wrongdoing, but also to discourage future crime. Deterrence theory suggests that punishment should therefore reflect both the harm caused and the likelihood that an offender will be caught. Across five experiments, we examined whether people adjust punishment judgments according to apprehension probability—the likelihood that an offender will be caught—and victim harm. In property harm cases, participants consistently recommended harsher punishments when apprehension probability was lower, and victim harm was higher. This pattern remained whether the victim was an identifiable individual, society more broadly, or the participant. Although participants responded to apprehension probability in the direction predicted by deterrence theory for property crimes, they did not adjust their judgments as strongly as economic models would prescribe. In bodily harm cases, apprehension probability did not influence punishment judgments. Instead, punishments were driven primarily by the severity of the harm. These findings suggest that people consider deterrence when judging crimes but place limits on how strongly the apprehension probability should affect punishment. This boundary highlights possible concerns in designing effective punishments that discourage crime.