A dual-task paradigm was used to infer the processes critical for episodic memory retrieval by measuring susceptibility to memory interference from different distracting tasks. Research suggests that retrieval interference occurs due to material-specific overlap between concurrent tasks. I tested whether interference could instead arise from processing-specific overlap. In Experiment 1, I took advantage of individual differences in how verbal materials could be represented in those with different language backgrounds. I compared recognition of studied information in English and Chinese speakers under full attention (FA) or under one of two different divided attention (DA) conditions. Participants viewed simplified Chinese characters or English words, and later completed recognition while simultaneously performing distracting tasks requiring phonological (DAP) or visuospatial (DAV) processing of auditorily presented letters. I found an interaction such that Chinese speakers were more susceptible to interference from the visuospatial than phonological distracting task, whereas the reverse pattern was shown in English speakers. These results suggest that interference with memory retrieval is processing-, not material-, specific, as both distracting tasks used the same materials. Next I sought to determine whether processing-specific interference could be observed within the visuo-spatial domain. Accordingly, in Experiments 2 and 3, I examined whether face recognition would be disrupted more by a distracting task requiring configural than featural processing. In Experiment 2, participants studied faces under FA and subsequently performed a recognition task under either FA or each of two different DA conditions in which a distracting face was presented alongside, requiring either a featural (DAF) or configural (DAC) decision. In line with a material-specific account of interference, face memory accuracy was disrupted in both DA conditions relative to the FA condition, although no processing-specific differences in interference were found between the DA conditions, likely because both distracting tasks engaged configural processing. To better isolate the different processing streams in Experiment 3, some faces were inverted to offset configural processing and to engage featural processing. I compared patterns of memory interference when target faces were presented upright (configural) or inverted (featural). I found a crossover interaction: memory for upright faces was worse in the DAC than in the DAF condition, whereas the reverse was true for inverted target faces, supporting a processing-specific account of memory interference. In Experiment 4, I sought to rule out task difficulty as an alternative explanation for the pattern of interference effects. I measured whether each distracting task produced similar slowing, which provides an indirect assessment of resource requirements of a task, on a simultaneously performed auditory tone discrimination task. Results showed that my distracting tasks were not differentially attention demanding, as indexed by similar accuracy rates for tone classification and response times on the tone discrimination task when performed concurrently with each distracting task. Findings suggest that the magnitude of memory interference under DA conditions at retrieval is influenced by material-specificity but that, critically, it also depends on the extent to which the processing demands of the distracting and retrieval tasks overlap. I have shown here that retrieval is not automatic or obligatory as others have suggested, but instead is subject to disruption. This thesis specifies that retrieval interference can occur due to competition for a limited pool of common processing resources across target and distracting tasks. Thus, when trying to recall studied information, one should avoid distracting conditions, especially those that overlap significantly not only with the type of materials tested but also with the mental processes required to retrieve that target information.

No description available.

This study examined how different background noise conditions affected the spoken language production of people with aphasia (PWA) when performing a story retell task. Participants included 11 adults with mild to moderate aphasia and 11 age- and gender-matched controls. Participants retold stories in a silent baseline and five background noise conditions (conversation, monologue, phone call, cocktail, pink noise). Dependent measures of speech fluency and language production measures (correct information units, lexical errors, lexical diversity, and cohesive utterances) were compared between groups and across conditions. Results reveal that background noise results in significantly lower communication efficiency (i.e., correct information units) for the aphasic group than the control group. PWA also experience background noise costs in relation to speech fluency and lexical production during both conversation and phone call conditions. The control group experience no significant background noise costs. These findings suggest that background noise interferes with discourse more for PWA than neurologically healthy adults.

While previous research has extensively examined the effect of acute stress on cognitive performance, relatively little research has explored the relationship between chronic stress and cognitive performance. The current study aimed to control for current state anxiety to better isolate more chronic stress, when examining the relationship with performance on divided attention tasks. Fifty-four university undergraduates, who self-reported a wide range of perceived chronic stress (10-item Perceived Stress Scale), completed the Trail-Making Test and a dual (auditory and visual) Continuous Performance Test (CPT). Hierarchical regressions were performed to explore cognitive predictors of chronic perceived stress. After covarying for state anxiety (state portion of State-Trait Anxiety Inventory), the most statistically significant predictor (via stepwise entry) was the auditory omission error change score (dual minus single condition), which showed a medium effect size (r = .36). Results have practical safety implications, as the implementation of an efficient and inexpensive measure of self-reported stress may predict future job-related errors in high-stress professions that require divided attention.

This study examined the impact of divided attention tasks on stress using physiologic measures. The divided attention conditions included speech tasks (conversation or procedural discourse) and non-speech computer-based tasks (visuospatial, mathematical, language, data entry, or text editing). Participants included 60 adults divided into two groups of 30 by age. The young adult group ranged in age from 18-30 years and the older adults ranged from 55-82 years. Participants were required to perform the speech task and the non-speech task in isolation as well as a speech task performed concurrently with each of the non-speech tasks. The order of the tasks was randomized between participants to reduce sequencing effects. Physiologic measures include heart rate (HR), heart rate variability (HRV), and galvanic skin response (GSR) using a physiologic measurement system. Statistical analysis revealed age-related physiologic differences during the performance of all tasks. All GSR measures were significantly lower in older adults. Findings also provide insight into the physiologic response to dual-task conditions. The GSR levels were lower in concurrent conditions when compared to the conversation only tasks. Additionally, GSR levels increased during math tasks when compared to visuospatial or language tasks. The results provided insight into the physiologic response to divided attention tasks. The lack of a resting baseline condition and the effects of age on the dependent measures complicated the interpretation of the findings. Further research is needed to better understand the impact of divided attention tasks on a speaker’s physiologic stress response.

We examined the neural and cognitive processes engaged during auditory verbal recognition performance under full attention (FA) and divided attention (DA) conditions in younger and older adults. Recognition was disrupted by a word (DA-word), but not digit-based (DA-digit) distracting task, performed concurrently with retrieval. In Study 1, a multivariate functional magnetic resonance imaging analysis technique, Partial Least Squares (PLS) was used to identify distributed patterns of brain activity most related to the different conditions and behaviours. We found that similar retrieval networks were recruited during the FA and DA-digit, but not DA-word, condition in both age groups, mirroring behavioural performance. There was, however, an age-related change in the brain regions that predicted successful memory performance. In addition, we found that a neural network relating to hippocampal activity predicted memory success during the FA and DA-digit, but not DA-word, condition in younger, but not older, adults. In study 2, we used a Remember-Know paradigm to examine how manipulations of DA affect recollective and familiarity-based retrieval processes. Younger and older adults showed an increase in false Remember responses during both DA conditions and decreased accuracy in Know responses only during the word-based DA condition. In addition, aging was associated with decreased accuracy in Remember, but not Know, responses, in both DA conditions. In a follow-up experiment, we showed that these results cannot be accounted for by differences in difficulty level of the chosen distracting tasks. Results suggest that recollective processes rely on attentional resources during retrieval. Together these studies show that declines in available attentional resources, common with advancing age, affect both the neural networks used during retrieval, and the qualitative nature of the memories that are retrieved. Results also suggest that familiarity processes rely on the reactivation of content-specific representations, mediated by a neural network relating to hippocampal activity in younger, but not older, adults.

The purpose of this study was to examine the bidirectional effects of simulated driving and conversations using different speaking modalities. Participants included 30 males and 30 females with no history of speech, language or hearing disorders. The participants were divided into three age groups: 20s, 40s, and 60s. They completed a driving simulation task in isolation and also while speaking on a hand-held or hands-free cell phone or with a passenger in the car. Speech measures included speaking time ratio, mean, and standard deviation of intensity, as well as mean and standard deviation of fundamental frequency in semitones. Driving measures included standard deviation of lane position, mean, and standard deviation of speed, standard deviation of steering wheel position, and the average number of steering wheel turns. There were significant effects of speaking while driving on mean intensity, speaking time ratio, standard deviation of steering wheel position, and the number of steering wheel turns. There were significant gender effects for speaking time ratio, standard deviation of intensity, and mean intensity, with the females having higher speaking time ratios, and the males having a higher standard deviation and mean of intensity. There was a significant age effect for mean fundamental frequency, standard deviation of lane position, and the standard deviation of steering wheel position. For mean fundamental frequency, the 60s group were lower than the 20s group. The 60s group had a higher standard deviation of lane position and standard deviation of steering wheel position. These findings reveal effects on both speaking and driving performance when speaking and driving concurrently. This has potential clinical implications for planning therapy activities that will help individuals generalize their learned skills from quiet, distraction-free clinic rooms to more realistic situations with distractions and background noise.

The effects of divided attention on speech in Parkinson's disease (PD) have been studied for a variety of tasks in recent years. Much of the previous research studied gait patterns while participants concurrently performed another task. There have been few studies regarding the effects of divided attention on speech in individuals with PD. The ability to communicate effectively relies in part on an appropriate rate of speech, vocal intensity, and fundamental frequency control. This study included 27 participants: 8 with PD, 12 neurologically healthy older (HO) adults, and 7 healthy younger (HY) adults. Each participant was given a list of topics to speak about during the experiment. They produced monologues under three conditions: standing, walking on a treadmill, and walking over obstacles on a treadmill. Each monologue was recorded and trimmed of pauses between topics, experimenter speech, and nonspeech behaviors before analysis. Speech rate, speaking versus pausing time, overall intensity, and intensity and fundamental frequency (F0) variability were analyzed. Median, mean, maximum, and minimum F0 increased as the gait task increased in difficulty. Mean and standard deviation of intensity also increased with gait demands. All groups had increased intensity variability when walking compared to standing. Speaking versus pausing time did not differ significantly as a function of the walking task and the results varied across the groups; the same was true for speech rate. These findings reflect changes in performance during divided attention tasks, with a greater effect on HO adults and individuals with PD than their younger counterparts.

We examined the neural and cognitive processes engaged during auditory verbal recognition performance under full attention (FA) and divided attention (DA) conditions in younger and older adults. Recognition was disrupted by a word (DA-word), but not digit-based (DA-digit) distracting task, performed concurrently with retrieval. In Study 1, a multivariate functional magnetic resonance imaging analysis technique, Partial Least Squares (PLS) was used to identify distributed patterns of brain activity most related to the different conditions and behaviours. We found that similar retrieval networks were recruited during the FA and DA-digit, but not DA-word, condition in both age groups, mirroring behavioural performance. There was, however, an age-related change in the brain regions that predicted successful memory performance. In addition, we found that a neural network relating to hippocampal activity predicted memory success during the FA and DA-digit, but not DA-word, condition in younger, but not older, adults. In study 2, we used a Remember-Know paradigm to examine how manipulations of DA affect recollective and familiarity-based retrieval processes. Younger and older adults showed an increase in false Remember responses during both DA conditions and decreased accuracy in Know responses only during the word-based DA condition. In addition, aging was associated with decreased accuracy in Remember, but not Know, responses, in both DA conditions. In a follow-up experiment, we showed that these results cannot be accounted for by differences in difficulty level of the chosen distracting tasks. Results suggest that recollective processes rely on attentional resources during retrieval. Together these studies show that declines in available attentional resources, common with advancing age, affect both the neural networks used during retrieval, and the qualitative nature of the memories that are retrieved. Results also suggest that familiarity processes rely on the reactivation of content-specific representations, mediated by a neural network relating to hippocampal activity in younger, but not older, adults.

The multiple object tracking task (Pylyshyn and Storm, 1988) has long been a standard tool for use in understanding how we attend to multiple moving points in the visual field. In the current experiments, it is first demonstrated that this classical task can be adapted for use in a simulated driving environment, where it is commonly thought to apply. Standard requirements of driving (steering, maintaining headway) are shown to reduce tracking ability. Subsequent experiments (2a, 2b, 2c) investigate the way in which participants respond to events at target and distractor locations, and have bearing on Pylyshyn’s (1989) “indexing” hypothesis. The final experiment investigates the effect of the colour-composition of the tracking set on performance, and may have implications for our theoretical understanding of how tracking is performed. / AUTO21, NSERC, CANDrive