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Title: An associative approach to task switching
Author: Forrest, Charlotte Louise
Awarding Body: University of Exeter
Current Institution: University of Exeter
Date of Award: 2012
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This thesis explores the behaviour of participants taking an associative approach to a task-cueing paradigm. Task-cueing is usually intended to explore controlled processing of task-sets. But small stimulus sets plausibly afford associative learning via simple and conditional discriminations. In six experiments participants were presented with typical task-cueing trials: a cue (coloured shape) followed by a digit (or in Experiment 5 a symbol) requiring one of two responses. In the standard Tasks condition (Monsell Experiment and Experiments 1-3), the participant was instructed to perform either an odd/even or a high/low task dependent on the cue. The second condition was intended to induce associative learning of cue + stimulus-response mappings. In general, the Tasks condition showed a large switch cost that reduced with preparation time, a small, constant congruency effect and a small perturbation when new stimuli were introduced. By contrast the CSR condition showed a small, reliable switch cost that did not reduce with preparation time, a large congruency effect that changed over time and a large perturbation when new stimuli were introduced. These differences may indicate automatic associative processing in the CSR condition and rule-based classification in the Tasks condition. Furthermore, an associative model based on the APECS learning algorithm (McLaren, 1993) provided an account of the CSR data. Experiment 3 showed that participants were able to deliberately change their approach to the experiment from using CSR instructions to using Tasks instructions, and to some extent vice versa. Experiments 4 & 5 explored the cause of the small switch cost in the CSR condition. Consideration of the aspects of the paradigm that produced the switch cost in the APECS model produced predictions, which were tested against behavioural data. Experiment 4 found that the resulting manipulation made participants more likely to induce task-sets. Experiment 5 used random symbols instead of numbers, removing the underlying task-sets. The results of this experiment broadly agreed with the predictions made using APECS. Chapter 6 considers an initial attempt to create a real-time version of APECS. It also finds that an associative model of a different class (AMAN, Harris & Livesey, 2010) can provide an account of some, but not all, of the phenomena found in the CSR condition. This thesis concludes that performance in the Tasks condition is suggestive of the use of cognitive control processes, whilst associatively based responding is available as a basis for performance in the CSR condition.
Supervisor: McLaren, Ian ; Monsell, Stephen Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: task-switching ; task cuing ; associative learning ; conditional discriminations ; computational modelling