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Title: The (questionable) role of neighbourhood density in verbal short-term memory
Author: Greeno, David James
ISNI:       0000 0004 9347 5442
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2019
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Neighbourhood density refers to the number of words that can be derived from a given word by changing a single phoneme (phonological neighbours) or letter (orthographic neighbours). Performance in verbal short-term memory (vSTM) tasks (e.g., serial recall/reconstruction) is usually best when to-be-remembered words are from dense rather than sparse neighbourhoods. This is typically used as evidence of short-term storage being supported by networks of long-term lexico-phonological knowledge. The primary aim of the thesis is to assess our current understanding of neighbourhood density and to consider what it really reveals about the nature of vSTM. This was achieved by adopting several approaches. Chapter 2 first identified and then investigated three key variables – modality, task type and word pool size – to assess the parameters required for a dense neighbourhood advantage in vSTM tasks to manifest. However, across 4 experiments, it was revealed that neighbourhood density does not have robust and general effects upon vSTM with an advantage for sparse neighbourhood words elicited in Experiments 3 and 4. The findings raise questions over several models of vSTM. Chapter 3 more closely examined the parameters used by some previous experiments that have investigated neighbourhood density and found that the distribution of onset letters within each word pool is often not controlled. Simulations were used to demonstrate that this oversight can produce analogous effects in serial reconstruction tasks if participants were to use part of the word (e.g., the onset letter) to inform the order of the originally presented sequence. If, in some instances, the distribution of onset letters within word pools was determining vSTM task accuracy then the usefulness of using those results to make specific claims about how neighbourhood density impacts vSTM is brought into question. Chapter 4 considered that neighbourhood density variations might exist because of effort minimisation during the development and evolution of language. It was found that words from denser neighbourhoods tend to consist of more effortful articulations and take longer to vocalise than words from sparser neighbourhoods. This raises the possibility that neighbourhood density distributions impact vSTM because dense neighbourhood words are generally easier to articulate, rather than dense neighbourhood words being better supported by networks of long-term lexico-phonological knowledge. Finally, Chapter 5 attempted to demonstrate that effects analogous to those found when neighbourhood density is manipulated can also be found when only articulatory difficulty is manipulated. However, articulatory difficulty failed to predict the outcome of three experiments. The results of the thesis are considered in relation to several models of vSTM and the concept of neighbourhood density and what role, if any, it plays in vSTM is critically discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: BF Psychology