The irrelevant sound effect (ISE) describes the disruption of processes involved in maintaining information in working memory (WM) when irrelevant noise is present in the environment. While some posit that the ISE arises due to split obligation of attention to the irrelevant sound and the to-be-remembered information, others have argued that background noise corrupts the order of information within WM. Support for the latter position comes from research showing that the ISE appears to be most robust in tasks that emphasize ordered maintenance by a serial rehearsal strategy, and diminished when rehearsal is discouraged or precluded by task characteristics. Evidence supporting such a stance has been used to create a narrow narrative in which the ISE should only emerge on tasks with ordered output demands, when a serial rehearsal strategy is used, and in the presence of changing-state auditory distractor sequences. However, an ISE has been documented in many situations that do not match the scenario described above, thus raising questions as to what specific factors and combination of factors give rise to the ISE. The present study aims to disentangle each of the proposed contributing variables to the ISE by using eight working memory tasks that vary based on demands and features in the presence of multiple sound conditions. Further, strategy use is assessed on a task-by-task basis using an informed, multi-step process. The results reveal patterns of the ISE that do not match the claims made by rehearsal-disruption nor attentional accounts, and instead support a narrative in which poor cognitive control likely leads to the adoption of ineffective strategies for memory maintenance, and the combination of such factors increases one’s susceptibility to disruption by irrelevant sounds. / Psychology

Humans engage with a variety of symbols in daily life. Perhaps the most common symbol form is language where we represent myriad concepts, ideas, and notions through strings of sounds and letters. Human communication is also facilitated through other non-verbal symbol modalities ranging from body language/gestures (e.g., crossed arms, thumbs up) to objects (clothing as an indication of social status), and signs (red octagon means stop). Child language research has explored symbolic cognition and its emergence in development, but fundamental questions remain regarding symbolic thinking in adulthood and the impact a symbolic deficit can have on communication. A novel, neurologically-constrained model of symbolic representation is proposed and investigated which aims to addresses open challenges in exploring symbolic cognition. In Chapter 1, SymCog, a novel toolkit to evaluate symbolic representation is developed and normed in a series of three studies. This toolkit and its task, the Symbol Identification Task, are premised upon matching animated video depictions of abstract concepts to their corresponding verbal and non-verbal symbols. Results showed individuals can consistently match different symbol modalities (words, images) to shared concept animations. Chapter 2 assesses performance in the Symbol Identification Task in neurotypical adults receiving inhibitory brain stimulation [i.e., transcranial direct current stimulation (tDCS) of the temporoparietal junction]. Chapter 3 evaluates two cases of persons with aphasia (PWA) in the same task. The goal of these studies was to isolate the neurological-constraints of the model and identify how symbol processing can be impaired. Findings showed reduced performance in the inhibitory stimulation group; highlighting the role of the temporoparietal junction in symbol processing. Results from PWA revealed one case had poor performance across both word and image symbol modalities. Chapter 4 further investigates neurological constraints of the model in an EEG/ERP study. This study assessed N400 deflections during a modified Symbol Identification Task, where frontal-central electrodes were most active. Taken together, these chapter findings suggested two cortical regions potentially support symbolic cognition, including the temporoparietal junction and left central frontal cortex. The results also suggest that impairments in one symbol modality (e.g., words in aphasia) might also present in other modalities for shared concepts. These studies offer insights regarding the cognitive mechanisms involved in symbolic cognition and how they can be impaired. With the use of contemporary tools, such as the SymCog toolkit, future research can better recognize the human capacity to understand and use symbols. / Communication Sciences

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Various infant studies suggest that statistical regularities in the speech stream (e.g. transitional probabilities) are one of the first speech segmentation cues available. Statistical learning may serve as a mechanism for learning various language specific segmentation cues (e.g. stress segmentation by English speakers). To test this possibility we exposed adults to an artificial language in which all words had a novel acoustic cue on the final syllable. Subjects were presented with a continuous stream of synthesized speech in which the words were repeated in random order. Subjects were then given a new set of words to see if they had learned the acoustic cue and generalized it to new stimuli. Finally, subjects were exposed to a competition stream in which the transitional probability and novel acoustic cues conflicted to see which cue they preferred to use for segmentation. Results on the word-learning test suggest that subjects were able to segment the first exposure stream, however, on the cue transfer test they did not display any evidence of learning the relationship between word boundaries and the novel acoustic cue. Subjects were able to learn statistical words from the competition stream despite extra intervening syllables.

Current Signal Detection Theory models of source memory necessitate assumptions about the underlying distributions of source strengths to describe source memory performance. The current experiments applied a modified version of the same-different task in order to plot individual memory stimuli along a controlled dimension of the average frequency of voices. This technique allowed us to determine that subjects were using an independent-observations strategy rather than a differencing strategy when deciding whether two test words were spoken by the same or different female speakers at study. By including two male and two female voices and changing the task distinction from same or different speakers to same or different genders, we predictably switched subjects’ decision strategies. With this new same-different memory design, we are one step closer to ending our reliance on measures that are inferred from data to describe subjects’ source memory performance.

This investigation examined the hypothesis that the presence of relationship threat leads to decreased working memory capacity, and also changes partner perceptions based on adult attachment style. To test this hypothesis, participants were exposed to a threat or no-threat manipulation and then completed measures examining partner perceptions and individual differences. Results suggest that the threat manipulation might have been strong enough for only highly anxious people. These individuals showed higher levels of working memory capacity following a relationship threat, compared to more securely attached persons, and later described their partners in more global, less desirable terms, regardless of threat condition. Highly avoidant individuals also described romantic partners in less desirable terms compared to more securely attached persons, regardless of threat condition. Individual difference measures suggest that rejection sensitivity and neuroticism may contribute to how romantic partners are perceived. Implications for future research on relationship threat and partner perceptions are discussed.

This thesis investigates the developmental trajectory of visuo-spatial working memory as well as the potential influence of acute exercise on working memory performance. Individuals between the ages of 6 and 25 years were randomly assigned to a 30-minute bout of exercise on an elliptical trainer or to a no-exercise control condition. Participants then performed a computerized N-back task to assess working memory. Developmental results suggest that working memory ability continues to develop into early adulthood with the exact trajectory depending on the cognitive demand of the task being assessed. No difference in working memory performance was found between the exercise and control conditions. Thus, acute exercise did not influence performance on the present working memory task, suggesting a need for more research in this area.

The most important predictors of fixation durations in reading are a word’s frequency of occurrence (as measured by counts in large corpora) and its predictability in context (as measured by cloze probability). Two recent eye-tracking studies investigated distributional effects of word frequency (Staub et al, 2010) and word predictability (Staub, 2011) separately. The present study investigates the distributions associated with these two variables when they are manipulated in the same experiment. When considering the overall means, frequency and predictability showed significant main effects (LF>HF; LP>HP), with no interaction. In addition, we found evidence supporting the previous distributional findings where frequency and predictability affect all fixations (causing a shift in the distribution), but frequency also has a special influence on the longest fixations. Interestingly, the model fits suggested that there was an interaction between the predictors in first fixation duration. However, this effect was not visible in the vincentiles (which are plots of the actual data) and it appeared to be conditional on four particular subjects. Since we did not find convincing evidence of an interaction in our distributional analysis, the present findings provide support for theories of fixation durations whereby frequency and predictability combine additively.

The test effect (Roediger & Karpicke, 2006) demonstrates that performance on a final test is better when an immediate test is taken after reading a passage rather than rereading. Although transfer appropriate processing has been suggested as a theoretical explanation, the results could be due to elaborative retrieval processes during the immediate test that are not available during restudy. We compared testing to three other strategies using elaborative retrieval—Generating Questions, Read-Recite-Review, Teaching—to determine whether they would be as beneficial as testing. Results showed that each of the alternative strategies produced final test performance equal to that of testing, suggesting not only that these strategies are as effective as testing, but also that elaborative retrieval can explain test effects. However, final test performance for testing was not better than rereading. This finding leaves unanswered questions, given that the test effect is a robust result in the literature.

Specific ERPs such as error- related negativity (ERN) and feedback- related negativity (FRN) reflect error processing/performance monitoring. The reinforcement learning theory of error processing suggests that ERN reflects the first detection of error commission. In order to elicit ERN, participants must perceive a response as erroneous. This implies that as learning occurs, ERN amplitude increases. A previous study (Horst, Johnson, & Donchin, 1980) examining the P300 component on a learning task demonstrated increased amplitude in response to violations of participants’ expectations about task events. The current study sought to replicate this finding while extending the analysis to include ERN and FRN amplitudes on incorrect trials. Participants completed a complex learning task in which they were required to learn 3 lists of paired nonsense syllables. Participants viewed a stimulus syllable, typed what they believed to be the correct response, then indicated their confidence level on a scale from 0- 100. Feedback was then presented regarding response accuracy. Each list was considered learned after 10 consecutively correct trials. Data from electrodes Fz, Cz, Pz, and Oz showed an increased ERN amplitude 50ms after error commission on incorrect trials. The ERN and FRN amplitudes were greater for incorrect trials than for correct trials. Larger P300 amplitudes were observed for trials in which participants’ outcome expectation was violated. This extension of previous findings provides further insight into the role of error processing in the context of reinforcement learning.