Peter Graf

Prospective Graduate Students / Postdocs

This faculty member is currently not actively recruiting graduate students or Postdoctoral Fellows, but might consider co-supervision together with another faculty member.


Research Interests

Human memory
Prospective memory
Affect and cognition

Relevant Degree Programs

Affiliations to Research Centres, Institutes & Clusters


Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - Nov 2019)
The cognitive processes involved in prospective memory task execution: response switching from an ongoing activity to a planned task (2019)

Prospective memory is the cognitive function used for carrying out planned tasks upon the occurrence of an appropriate cue. Prospective memory tasks are uniquely challenging because they typically take place while we are otherwise engaged in another ongoing activity. In order to carry out a planned task, three retrieval stages are required: cue noticing, meaning the cue is processed by the sensory system and perceived as a distinct entity; recognition of cue-plan relevance, meaning that the representation of the plan is activated in connection with the cue; and response switching, meaning ongoing activity responding is interrupted and the planned task response is executed. Previous prospective memory research has focused on manipulations and theoretical explanations most relevant to the first two stages. The research presented in this dissertation examined the cognitive processes involved in response switching. In Experiments 1 and 2, a prospective memory task was embedded within the encoding phase (Experiment 1) or retrieval phase (Experiment 2) of a recognition memory test. I examined the pattern of processing for ongoing activity words immediately preceding and following a prospective memory task response. Participants responded more slowly, and recognition test performance was lower, for words immediately following prospective memory task responses. Experiment 3 tested the possibility that the proactive effects observed in Experiments 1 and 2 were a result of processing a distinctive stimulus. For words immediately following distinctive stimuli, participants responded more slowly, but there was little influence on recognition test performance. In Experiments 4a and 4b, the degree of overlap in the processing required for the ongoing activity and the prospective memory task cue was manipulated. Participants showed larger proactive effects when there was a greater degree of overlap. The goal of Experiment 5 was to explore how subliminal primes preceding the prospective memory task cue would influence proactive effects due to response switching. The results showed that category primes produce larger proactive effects compared to repetition primes. Taken together, these findings support the assumption that two mechanisms identified in the task-switching literature, task-set configuration and task-set inertia, are involved response switching in prospective memory task retrieval.

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Timing everyday tasks and events (2017)

Many of the tasks we complete every day require us to attend to the passing of time or to use time information in some way. Everyday tasks frequently require us to use time information in a strategic, deliberate, and explicit way, such as when we wish to steep a cup of tea for 3 minutes or must leave to meet a colleague in 5 minutes. Much of the previous research on timing has used very short duration tasks, in the range of seconds. Several models have been developed to account for timing in short duration tasks, but it is not known which model(s) best fit timing of everyday intervals. This dissertation research was designed to determine whether the AGM or memory storage models can account for timing in the range of everyday intervals. Experiment 1 investigated the underlying pattern of estimates in the range of 1-5 minutes. Participants produced underestimates for all intervals. Experiments 2 and 3 used a framing manipulation to investigate the role of memory chunking in timing everyday durations. Participants who were instructed to focus on the present task produced intervals that were longer than participants who were instructed to focus on a future task, consistent with the idea that a present frame serves as a better organizing structure for the interval and results in fewer chunks. According to memory storage models, the number of items in memory is compared to a stored value in reference memory to determine how much time has passed. When stimuli are organized more cohesively, resulting in fewer chunks, it takes a longer time to accumulate the target number of chunks. Experiment 4 used feedback and an attentional manipulation to investigate the role of reference memory and attention to timing. Participants produced more accurate intervals following feedback, consistent with the idea that reference memory for everyday intervals is inaccurate. Attention had no effect on estimate duration, which is inconsistent with the AGM. Taken together, the results from these experiments suggest that memory storage models are a better fit for timing in the range of everyday intervals.

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The prospective memory deficit theory of compulsive checking (2008)

Checking compulsions are the most common manifestation of obsessive-compulsivedisorder (OCD), yet the mechanisms which contribute to them are not well understood.According to one prominent theory — the memory deficit theory — individuals’ compulsions tocheck are fueled by a deficit in memory which makes it difficult for them to rememberperforming a previous action (e.g., locking a door). The main goal of this dissertation is toexamine the link between memory deficits and checking compulsions. This examination incarried out in the context of two domains of memory: retrospective memory and prospectivememory.A review of the literature on memory in OCD shows that previous research on thememory deficit theory has focused almost exclusively on the domain of retrospective memory,the ability to remember previously learned information and events. More importantly, the reviewdemonstrates that deficits in this domain of memory are not unique to checkers and thereforedo not hold the power to explain the compulsion to check. The review further examines thememory deficit theory in the domain of prospective memory, the ability to remember to carry outactions (e.g., lock a door). It reviews two of the studies presented in the dissertation whichdemonstrate deficits in sub-clinical checkers’ prospective memory and it provides somesupplementary analyses which show that deficits in prospective memory are unique to checkersand therefore may hold the power to explain the compulsion to check.Three empirical studies demonstrating that sub-clinical checking compulsions areassociated with subjective and objective deficits in prospective memory comprise the body ofthe dissertation. Two of the studies show that the link between checking compulsions andobjective deficits in prospective memory is direct and independent from elevations indepression, anxiety and distractibility associated with checking compulsions.The results are used as initial support for the theory that checking compulsions maydevelop in part as a compensatory reaction to deficits in prospective memory. If individualsfrequently forget to perform tasks they may develop intrusive doubts about whether theyperformed important tasks and when the perceived consequences of a failure are serious thesedoubts may lead to checking.

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Master's Student Supervision (2010 - 2018)
The eye of the beholder: Discrepancy reactions and prospective memory retrieval (2013)

How do we react to cues that we process differently than expected? Discrepancy- attribution theory posits that cognitively processing targets with differing quality generates a discrepancy response that influences cognitive decisions. To test this assertion, I conducted a series of four experiments designed to investigate the role of a discrepancy-attribution mechanism in making rating judgments on abstract stimuli that differed in colour saturation.Studies I and II required students to discriminate between pairs of virtual grid patterns displayed in red, blue and green. Results on a same-different judgment task revealed very similar patterns of speed and task accuracy across colours, with poor performance on paired displays with only a small saturation difference but excellent performance when paired displays differed by larger increments of saturation scale points. These two studies provided a saturation discrimination curve, which could be used to find appropriate standard and discrepant stimuli for future work.In Experiments III and IV, I used this pilot data to then induce discrepancy reactions by first creating and then violating either strong or weak cognitive expectancies of the perceptual processing of grid patterns. Students were then required to make beauty judgments of these patterns.Results of Experiment III and IV revealed that discrepancy reactions caused faster response times when discrepant stimuli differed in a positive direction. Taken together, these findings can shed new light on the role of discrepancy reactions in cognitive judgments, and prospective memory.Discrepancy Attribution Theory has been proposed as the primary mechanism underlying prospective memory (ProM) retrieval, and these new results have implications for ProM cue retrieval as well as far-reaching applications for decision-making, advertising, and consumer behaviour.

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Time Judgements in Dual-task Conditions (2010)

Every day we complete a number of tasks which require us to accurately time events, from estimating how long it will take us to drive to work in the morning to steeping our afternoon tea for the correct duration. Although timing is very important in our everyday lives, we know relatively little about how we process time information. Many models have been proposed to account for human timing, with the most prominent are the attentional gate model (AGM) and the multiple resources model. The AGM and the multiple resources model make many similar predictions about human timing, and it is often difficult to discriminate between the two. Toward this goal, the present research focused on a situation in which the two models make opposing predictions, that is, conditions which require participants two carry out two tasks concurrently with both of them requiring time-related processing.. Three experiments are reported, in which subjects were asked to estimate various shorter or longer intervals while concurrently carrying out a task that either required processing of time-related information or non-time based information. Results of all three studies seem more supportive of the multiple resources model of timing, rather than the AGM.

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