This research explores auditory short-term memory (STM) capacity for non-linguistic sounds in 10-month-old infants. Infants were presented with auditory streams composed of repeating sequences of either 2 or 4 unique instruments (e.g., flute, piano, cello; 350 or 700. ms in duration) followed by a 500-ms retention interval. These instrument sequences either stayed the same for every repetition (Constant) or changed by 1 instrument per sequence (Varying). Using the head-turn preference procedure, infant listening durations were recorded for each stream type (2- or 4-instrument sequences composed of 350- or 700-ms notes). Preference for the Varying stream was taken as evidence of auditory STM because detection of the novel instrument required memory for all of the instruments in a given sequence. Results demonstrate that infants listened longer to Varying streams for 2-instrument sequences, but not 4-instrument sequences, composed of 350-ms notes (Experiment 1), although this effect did not hold when note durations were increased to 700. ms (Experiment 2). Experiment 3 replicates and extends results from Experiments 1 and 2 and provides support for a duration account of capacity limits in infant auditory STM.

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Research on visual working memory (VWM) suggests a capacity limit of three to four objects (Luck & Vogel, 1997), but recent studies on the fidelity of VWM capacity for objects indicates that informational bandwidth, which can vary with factors like complexity and amenability to perceptual grouping, can interact with this capacity (Brady, Konkle & Alvarez, 2011). For example, individual features can be grouped into objects for an added benefit in VWM capacity (Xu, 2002). Along these lines, the Gestalt principles of proximity and connectedness have been shown to benefit VWM, although they do not influence capacity equally (Xu 2006; Woodman, Vecera & Luck, 2003). Closure, which has not been investigated for its influence in VWM capacity, is similar to connectedness and proximity as it promotes the perception of a coherent object without physical connections. In the current experiment, we evaluated whether closure produces similar or greater VWM capacity advantages compared to proximity by having participants engage in a change detection task. Four L-shaped features were grouped in tilted clusters to either form an object (closure condition) or not (no-object condition), with a set size of two (8 L features), four (16 L features), or six clusters (24 L features). Following a brief mask (1000 ms), the orientation of one cluster was changed (tilted 25 or -25 degrees) on half the trials. Our results indicate that there was no difference in accuracy or reaction time for the perceptual grouping conditions of closure/no-object, although we did find a main effect for set size and change conditions. Overall, it seems that grouping by closure provides no further advantages to VWM capacity than proximity; however, more experiments need to be conducted to solidify the findings of the current experiment.

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Listening ability is affected by external factors such as background noise and internal factors such as attention-allocation. I varied listening conditions and cognitive load and evaluated auditory word recognition and ratings of listening effort. Additionally, I investigated how individual differences in working memory capacity affected word recognition, recall, listening effort, and how working memory capacity interacted with other factors. Rönnberg et al.’s (2013) Ease of Language Understanding (ELU) model states that individual differences in working memory capacity will lead to differences in language comprehension in challenging listening conditions, where those with higher working memory capacity will be better at speech recognition. Using a dual-task experiment, participants heard and repeated words presented in three listening conditions: masked with pink noise, masked with babble, and processed through a hearing loss simulator. To manipulate cognitive load, participants completed the speech recognition task in both single- and dual-task paradigms. In the dual-task paradigm, participants continuously tracked a pseudo-randomly moving target on a screen for half the experiment. Participants reported perceived listening effort for each combination of listening condition and tracking condition. Additionally, memory for correctly heard words was tested with a recognition memory test. Word recognition performance and listening effort rating data agreed with my hypotheses that difficult listening conditions would produce poorer word recognition performance and increased listening effort. Interesting effects of cognitive load are discussed. The relation between working memory capacity and performance on various measures is also discussed in the context of the ELU model and theories of working memory capacity. Internal and external factors clearly interact to affect listening, and this interaction varies across individuals. / Thesis / Master of Science (MSc) / The ability to hear is affected by many factors, including attention and memory. The goal of this research is to investigate the cognitive factors (attention and memory) that affect hearing and how these effects differ on an individual level. My findings contribute to a better understanding of how background noise and mental demand affect hearing ability and listening effort, as well as how individual differences in cognitive ability further influence these factors. Results suggest that background noise and increased mental demand will decrease listening ability and increase listening effort. These changes in listening differ according to individual cognitive ability.

The majority of memory research, and research on its cognitive underpinnings has thus far focused on retrospective memory, or memory for things learned or rehearsed in the past. More recently, however, prospective memory, or the memory for future intentions, has become a major area of research. It is theorized that prospective and retrospective memory may both rely on similar constituent parts such as working memory and selective attention; the relationship between these constructs and prospective memory is, however, significantly less clear than for retrospective memory. In this study we sought to further clarify the role that cognitive process play in prospective memory performance using an SEM approach that included monitoring as a mediating variable in addition to focal, non-focal, and time-based prospective memory task condition. Results suggest a monitoring component is important in both focal and non-focal conditions, and that the type of monitoring observed in this study is related primarily to proactive interference, and reflects participants’ ability to disengage from no longer relevant stimuli¬¬¬.

Recent research has implicated working memory in unconscious tasks, controversially shifting the viewpoint of conscious access necessitating working memory functions (Soto, Mäntylä & Silvanto, 2011). The aim of this study was to investigate the flexibility of unconscious working memory using continuous flash suppression (CFS). Participants (n=18) completed a simple delayed-match-to-sample (DMS) task. Two conditions required the matching of either objects or spatial locations. CFS was used to render stimuli invisible and the perceptual awareness scale (PAS) helped to determine subjective conscious experience. Analysis determined no significant findings in d’ or reaction times. This confirmed the null hypothesis, that there would not be an affect on working memory due to presentation of visually suppressed information. These results may have been due to a lack of effect, complexity or procedural issues. Further research is needed to elucidate these non-significant results. This is especially critical since alternative methods examining unconscious working memory have found significant results.

This paper investigates the influence of readers' linguistic proficiency level and working memory functions on the reading behaviors and processes of readers of Arabic as a foreign language (henceforth RAFL). Two aspects of reading comprehension, speed and accuracy, are examined in light of readers' word decoding efficiency, recall performances, response times, scores, and readers' responses to two quantitative tests: a questionnaire and an interview. Twenty-four subjects participated in this study and were divided into two subgroups based on their proficiency level. The proficiency of these subjects was determined based on their academic level and their overall GPA in Arabic. All subjects completed a series of reading passages, in two separate sessions, followed by comprehension questions. Reading and answer time on the reading passages and questions were timed and scored. Data was also collected retrospectively using a questionnaire and an interview. The results suggest that reading comprehension and the ability to select and implement specific reading processes are impacted by the proficiency level of subjects as well as their word decoding skills. A strong correlation between comprehension outcomes and working memory functions was also found. That is, working memory capacity was found to be influential on the reading behaviors of readers especially at the sentence level with better performances reported for readers with larger and more elaborate vocabulary repertoire. Based on these results, some implications and conclusions are discussed for both Arabic reading research and foreign language classroom.

As life expectancy increases in modern societies, a greater importance has recently started to be given to cognitive aging. Alzheimer's disease (AD) affects the memory capability of individuals at advanced ages, independently of their general physical health. However, AD is suggested to have an undetectable development many years prior the first clear behavioral symptoms. This silent presence of AD may allow scientists to detect its initial stages, at which a combination of prevention treatments, such as medication and cognitive training, can be more effective. This study extends a line of research that aims to identify possible 'silent' biomarkers of AD using working memory performance and electrophysiological recordings (EEG) in healthy adults. Working memory (aka., short-term memory) is a memory sub-type used in everyday life that allows us to execute tasks in short periods of time. Given the significant parallels of working memory with other forms of long-term memory and its clear facility to be employed in experimental settings of short duration, working memory is a suitable candidate to identify early biomarkers of memory deficits ingeneral. In this study we assessed the cognitive performance and the electrophysiological response - via EEG signals - in a visual working memory recognition task that included the interference of past memories over the present ones. This 'proactive interference' effect is evaluated has a possible biomarker candidate for AD. Our findings reveal that subjects take longer reaction times in the recognition of visual items in the proactive interference condition in comparison to no interference. Additionally, we report an early (170-180 ms) and a later (430-450 ms) EEG components (ERP) that underlies the neural processing responsible for the resolution of this working memory interference. These two time intervals are interpreted as revealing the resolution of proactive interference at two difference stages of visual information processing ('letters'): the phonological (sub-lexical) and semantic (lexical) levels respectively. / --

<p>Higher-order cognitive functions, such as executive function (EF) and intelligence, are crucial to the everyday functioning of human beings. Gaining knowledge about these functions is important for our general understanding of human nature as well as for our ability to help those who may not develop these processes optimally. The present thesis focused particularly on the EF component working memory (WM), described as the ability to maintain informa-tion in consciousness during short time periods with the purpose of using that information in complex cognition. The major aims of the thesis were to increase our understanding of higher-order cognition in children as well as of deficiencies in intelligence found in children with Attention Deficit Hyperactivity Disorder (ADHD). We approached these aims by studying the interrelations among EF-related components in terms of their independent contributions to intellectual functioning. We also studied whether the lower intelligence in children with ADHD was mediated by fundamental EF-related components or whether these deficiencies went beyond the weaknesses in these specific cognitive functions.</p><p>Interpreting the present data, we suggest that intellectual functioning in children is best viewed as representing a system of primarily independent parts that may be accompanied by an overarching common mechanism. The multiple components involve, but are surely not limited to, WM functions, inhibitory functions, sustained attention, and processing speed. One of these functions, WM, was found to be further partitioned into domain-specific executive WM processes and domain-specific short-term storage processes, all of which constitute important aspects of higher-order cognitive functioning. We have further learned that deficits in fluid intelligence in children with ADHD may entail more than weaknesses in specific central cognitive functions. This additional deficit is cautiously interpreted as involving supe-rior executive attention functions setting the stage for the development and integration of the EF system as well as the “intelligence system”.</p>