Edwards, Timothy L.Yee, Journie2026-05-202026-05-202026https://hdl.handle.net/10289/18288Domestic dogs (Canis familiaris) are known for their excellent sense of smell, which is widely used to assist humans with important tasks. Despite this, there is limited research on how a dog's hunger state might influence their performance in scent-detection tasks. Previous research suggests that dogs demonstrate higher accuracy in search tasks when tested within 30 minutes of breakfast consumption. However, the underlying mechanisms are not clear, and whether similar effects might also occur in scent-detection tasks is unknown. One possible explanation is the glucose effect, which suggests that a recent meal improves cognitive performance. Alternatively, motivating operations (MO) theory suggests that feeding state modifies the dogs’ behaviour by changing the reinforcing effectiveness of food. Under this framework, recent food consumption is an abolishing operation (AO) that decreases the value of reinforcement and narrows stimulus control, while not eating recently is an establishing operation (EO), that increases the value of reinforcement and broadens response bias. This study evaluated scent-detection performance using an alternating-treatments design across breakfast (AO) and non-breakfast EO conditions. To prevent ceiling and floor effects, task difficulty was adjusted by increasing the formal similarity between target (discriminative stimulus; Sᴰ) and non-target odours across experimental phases. We hypothesised that the dogs would perform more accurately on the scent-detection task on breakfast days, as the absence of breakfast may increase the likelihood of false alarm indications, thereby reducing accuracy. Results showed that hit rates remained high, 89% across all phases in both conditions, and across individual sessions, ranging from 87%-93% for breakfast and 82% 94% for non-breakfast conditions. While correct-rejection rates were significantly higher on breakfast days (p = .016). This suggests that the AO narrowed stimulus control, whereas the EO broadened generalisation. A measure of log d and correct rejection rates improved significantly over time (p = .025; p = .014), suggesting that, cumulative food reinforcement (AO) throughout the day refined discrimination. These findings suggest that a recent meal functions as a MO which influence the precision of stimulus control, instead of, or possibly in addition to, a glucose effect.enAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.motivating operationsstimulus controlstimulus generalisationcanine scent detectionpre/post feedingThesis