Memory links our experiences together. Remembering one thing can remind of us another. This can be a blessing, as when a song transports you back in time to relive a fond memory. Or it can be a curse, as when seeing a colleague reminds you of a missed deadline. Controlling which memories come to mind influences one's well-being. This research will study why certain memories become linked and the processes that allow us to search for specific memories and avoid others. Existing work has often used tasks that simplify real-world memories by having participants only study random words. We will look at how adding real-world complexities to tasks impacts behavior. Another feature of our work is the use of computer models to simulate the cognitive mechanisms hypothesized to underlie memory search. These simulations allow us to evaluate theories of memory. This work will also help educate the next generation of scientists. We will train graduate students in our laboratory and develop a workshop for local high schools. Students will collect and analyze data. This will introduce them to both memory science and computer programing.
The research has two scientific objectives: Objective 1 is to elucidate the computational basis of interactions between time-based and meaning-based associations. Events that occur nearby in time tend to be related by meaning, but typical free-recall tasks lack meaning-based relations between items. Therefore, subjects rely heavily on time-based associations to guide memory search: recalling a word and using it as a cue to recall another that was studied nearby in time. But recent data reveal that subjects all but abandon time-based associations when lists contain strong meaning-based associations. To ascertain how temporal and semantic information interact to guide memory search, our experiments will vary the number and nature of semantic associations in lists. Our simulations will test the hypothesis that such interactions can be explained by representing semantic similarity and temporal proximity in separate layers of a network. Objective 2 is to elucidate the computational principles enabling control processes to change the dynamics of memory encoding and search. We often form new memories without trying and later find that cues bring them spontaneously to mind. Other times, we deliberately encode information which we will need to accomplish some goal. But most laboratory memory tasks are not quite like these situations: subjects deliberately memorize items but only for the sake of rote memory and not for a specific goal. Recent data show that both incidental and goal-directed encoding markedly alter subjects' reliance on time-based associations. This suggests that control processes, which allow the memory system to adapt to different task demands, are critical determinants of how memory is organized. To ascertain how control processes change the balance of time- vs. meaning-based organization during both encoding and retrieval, our experiments will provide subjects with a goal and vary the type of association most relevant to that goal. Our simulations will test the hypothesis that the influence of goals can be accounted for by adding a goal representation layer to the network.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
