Semantic, phonological and episodic representations in verbal immediate serial recall

Psycholinguistic frameworks provide contemporary accounts of immediate serial recall (e.g., N. Martin & Saffran, 1997; R. C. Martin, Lesch, & Bartha, 1999). These models emphasise the inclusion of semantic/associative and phonological representations in verbal short-term memory but have difficulty explaining how serial order is represented and maintained. Conversely, computational models of immediate serial recall (e.g., Brown, Preece, & Hulme, 2000; Henson, 1998b; Lewandowsky & Farrell, 2008b; Page & Norris, 1998) have typically concentrated on the role of temporary episodic representations on short-term recall but have trouble accounting for the influence of multiple representations on performance. The aim of this research was to combine these two lines of research to form a more integrative approach to immediate serial recall. The intention was to contribute to current understandings of verbal short-term memory by exploring how the binding of semantic/associative, phonological and episodic representations would influence immediate serial recall. The Deese-Roediger-McDermott (DRM) false memory paradigm was used as a framework to investigate the role of pre-existing phonological and semantic/associative knowledge on short-term memory. In line with the DRM framework and the embedded components model of working memory (Oberauer, 2002), the underlying assumption of this project was that long-term knowledge was arranged within pre-existing interconnected semantic and phonological networks that could communicate via spreading activation (Collins & Loftus, 1975). In Experiments 1 4, 80 adults aged between 18 53 years (M = 28.83, SD = 8.94) completed two computer-based immediate serial recall tasks during individual face-toface testing sessions. Each task was comprised of 40 six-word trials. To study phonological and associate/semantic binding, the type of items within each list were manipulated such that SEMANTIC, PHONOLOGICAL, EPISODIC REPRESENTATIONS IN SERIAL RECALL 14 lists were phonologically similar or dissimilar and associatively related or unrelated to a never-presented critical lure. “Pure” lists contained items that were either phonologically similar (e.g., rum) or semantically associated (e.g., jog) to the critical lure (e.g., run) interleaved between unrelated and dissimilar words. In contrast, “hybrid” trials comprised both items that were phonologically similar and items that were associatively related to the critical item. Unrelated lists contained items that were not connected to a common critical lure or to each other. To examine episodic binding, lists were presented at either a standard rate (i.e., one word per 1,000 milliseconds) or a rapid rate (i.e., one word per 250 milliseconds). Episodic binding was also manipulated by having participants repeat the same recall task or by giving participants two similar recall tasks to complete. The time between the two tasks was also varied such that participants completed the tasks in immediate succession, or after a 15-minute or 60-minute delay. In Experiments 5 and 6, healthy ageing was examined as a way to further examine episodic binding. Forty older adults aged between 67 92 years (M = 75.85, SD = 6.17) with no reported cognitive impairments completed a similar procedure to that of the younger participants. In all experiments of this project, responses were scored for serial recall and false recall and a series of factorial ANOVAs were run to analyse the results. Across all six experiments, the false memory effect was observed and false errors were reported to be significantly more likely during hybrid lists (p < .001) compared to other list types. Lures were also typically recalled towards the end of the list, under conditions in which episodic information was presumably at its weakest. False recall was not consistently impacted by age, presentation rate, or task repetition but these variables did influence true memory. Serial recall improved significantly with repetition (p < .01) across both age groups and younger adults tended to recall more items in position than older adults (p < .05). In SEMANTIC, PHONOLOGICAL, EPISODIC REPRESENTATIONS IN SERIAL RECALL 15 addition, serial recall was significantly greater during standard as opposed to rapid presentation rate (p < .05) for younger individuals. Together, these results support the notion that semantic/associative and phonological information is organised in pre-existing long-term networks and that the binding of this information can impact verbal short-term memory. These long-term activations appear to impact memory immediately after list presentation and persist for some time after the list has been recalled. The findings of this project also suggest that short-term recall is impacted by the strength and distinctiveness of temporary episodic content-context associations. Seemingly, episodic information can assist in maintaining order within the short-term system and also help one to ignore irrelevant activated representations in memory. In addition, how these temporary episodic bindings interact with long-term semantic and phonological networks also appears to be important to serial recall performance. The outcomes of this thesis highlight the role of semantic/associative, phonemic and temporary episodic binding in verbal short-term memory, and have implications for contemporary accounts of immediate serial recall. Some of these findings can be explained using the embedded components model (Oberauer, 2002) whilst others are more consistent with either psycholinguistic (e.g., R. C. Martin et al., 1999) or computational frameworks (e.g., Brown et al., 2000, 2007; Burgess & Hitch, 2006; Page & Norris, 2009). However, no current models of immediate serial recall are able to accommodate for all of the results of this project, providing support for the need for an integrative approach to short-term recall. SEMANTIC, PHONOLOGICAL, EPISODIC REPRESENTATIONS IN SERIAL RECALL 16 Chapter One: Chapter Overviews The overarching aim of this project was to examine the influence of associative/semantic, phonological, and episodic information on verbal short-term memory. The intention was to contribute to current understandings of immediate serial recall and contemporary frameworks of short-term memory. In particular, the purpose was to present an integrative model that could accommodate for the effects of both semantic and episodic memory on short-term recall. With this goal in mind, Chapter Two outlines the verbal shortterm memory system and provides an introduction to contemporary models of immediate serial recall. This includes a discussion of frameworks that have focused on the role of phonological and/or semantic information in short-term memory tasks as well as those that have emphasised the impact of episodic information on performance. The aim of this chapter was to develop the rationale that short-term memory research would benefit from a more comprehensive account of immediate serial recall than what is currently available in the literature. That is, an integrative model that is able to describe the role of semantic, phonological and episodic information in verbal short-term memory. The three subsequent chapters then discuss the manipulation of semantic, phonological and episodic information. These chapters are separated into the ways in which (1) semantic and phonological information and (2) episodic material are operationalised in this project. In order to manipulate semantic and phonological information in the immediate serial recall task, this project employed the Deese-Roediger-McDermott (DRM) false memory paradigm (Deese, 1959; Roediger & McDermott, 1995). Hence, Chapter Three provides a description of this procedure and its application within both the shortand long-term domain. To vary episodic information in the current project, healthy ageing was investigated. Therefore, SEMANTIC, PHONOLOGICAL, EPISODIC REPRESENTATIONS IN SERIAL RECALL 17 Chapter Four summarises the influence of the normal ageing process on memory performance and outlines the key theoretical perspectives of age-related declines in cognition. The purpose in discussing memory and ageing at this point of the thesis was to provide a foundation for the inclusion of an ageing sample as a way to further manipulate episodic information in the immediate serial recall task. The inclusion of an ageing sample was also intended to assist in investigating and extending the possibility of an integrative model of verbal short-term memory. As an additional means to manipulate episodic information, this thesis manipulated presentation rate and repetition of the immediate serial recall task. Chapter Five details the ways in which these variables have been utilised in other short-term memory studies and their employment in false memory research. After the relevant literature has been reviewed, Chapter Six delivers a general rationale and overview to the research, summarising the key points raised in the earlier chapters. The general aims and theoretical assumptions and predictions underpinning this thesis are included in this section to provide a basis for the experiments of the project. The six experiments of this thesis are detailed in Chapter Seven, Chapter Eight and Chapter Nine. The overall aim of these experiments was to investigate the binding of semantic/associative, phonological and episodic information, and the ways in which this information would influence true and false immediate serial recall. All experiments involved two immediate serial recall tasks using the DRM paradigm (Deese, 1959; Roediger & McDermott, 1995) and varying speeds of presentation. A general discussion of the results of these experiments are provided in Chapter Ten and implications for these findings in relation to an integrative model of immediate serial recall are considered in Chapter Eleven. In addition, the contributions that this project makes to verbal short