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Accumulating evidence about what prospective memory costs actually reveal
Luke Strickland1, Andrew Heathcote2, Roger W Remington3
1The School of Psychology, The University of Western Australia.
Summary
Prospective memory (PM) costs arise from increased response caution, not slower processing. This study used decision modeling to show that both focal and nonfocal PM tasks increase response thresholds, especially for word targets.
Area of Science:
- Cognitive Psychology
- Neuroscience
- Decision Science
Background:
- Event-based prospective memory (PM) tasks involve withholding an ongoing task response to perform a PM action upon target detection.
- PM task performance often incurs costs, indicated by slower ongoing task responses, traditionally attributed to capacity sharing reducing processing rates.
- Previous decision modeling studies on PM costs have been debated regarding whether costs reflect changes in processing speed or response caution.
Purpose of the Study:
- To investigate the underlying mechanisms of prospective memory costs using computational modeling.
- To differentiate between capacity-sharing (processing speed reduction) and caution-based (response threshold increase) explanations for PM costs.
- To examine how focal versus nonfocal PM task demands influence these mechanisms.
Main Methods:
- Employed the Linear Ballistic Accumulator and Diffusion Decision Model to analyze data from a lexical-decision task with semantic category-defined PM targets.
- Compared PM costs in nonfocal (semantic category) and focal (single target) PM conditions.
- Analyzed response times and accuracy for word and nonword trials.
Main Results:
- Prospective memory costs were consistently driven by increases in response threshold (caution), not by decreases in processing speed (drift rate).
- Both focal and nonfocal PM tasks led to increased thresholds, which were larger for word trials compared to nonword trials.
- Nonfocal PM instructions, unlike focal ones, also increased the threshold for nonword trials, suggesting a global increase in caution due to perceived task complexity.
Conclusions:
- Decision modeling supports a caution-based account of prospective memory costs, where individuals increase response thresholds rather than reduce processing speed.
- The findings suggest that PM targets (words) prompt increased thresholds to allow more time for retrieval, particularly under nonfocal conditions.
- Nonfocal PM tasks appear to induce a broader increase in response caution, likely reflecting heightened perceived task demands.