Exploring interactions between long-term and working memory using the Hebbian repetition effect Kathryn L. Gigler & Paul J. Reber, Department of Psychology, Northwestern University, Evanston, IL WM is often referred to as a gateway for LTM, though the systems also interact in the opposite direction This can be seen in the ability of experts to maintain large quantities of domain-specific information in mind, as LTM supports expanded WM capacity for this information 1 The Hebb repetition effect can be seen as an in-lab demonstration of this; participants perform better on material that was presented repeatedly than on material that was not in a WM task 2 Whether this effect can be observed when the repeated material is presented in fragments, and whether the effect occurs with or without explicit awareness, remain controversial 3 Can the Hebb repetition effect be observed in a novel task where the repeated sequence is presented in fragments? What is the relationship between LTM, awareness, and WM under these conditions? Introduction ConclusionsSeVi task and methods 1.Ericsson, K.A. & Kintsch, W. (1995). Long-term working memory. Psychol Rev, 102(2): Hebb, D.O. (1961). Distinctive features of learning in the higher animal. In J.F. Delafresnaye (Ed.), Brain mechanisms and learning, Oxford: Blackwell. 3.Couture, M. & Tremblay, S. (2006). Exploring the characterisitcs of the visuospatial Hebb repetition effect. Memory & Cognition, 34(8), Sanchez, D.J., Gobel, E.W. & Reber, P.J. (2010). Performing the unexplainable: Implicit task performance reveals individually reliable sequence learning without explicit knowledge. Psych Bull & Review, 17(6), Gigler, K.L. & Reber, P.J. Sequence-specific and non-specific gains in working memory. Under revision. Acknowledgements: Funding for this work was provided by the Department of Psychology and the Family Institute of Northwestern University. References The repetition effect was observed (in some participants) at a presentation rate of 40% repeated/80% random, but not at 20% repeated/80% random Suggests that sequences must be of a certain length in order to learn statistical regularities between items when sequence is fragmented As measured by the repetition effect and recognition test, advantage for repeated material occurred only if participants were aware of the repeated sequence This advantage was enhanced for higher- span participants, indicating a “rich get richer” effect Sequential visuospatial working memory task (SeVi-WM) 4,5 Presentation Phase (A) Sequence of cues scroll vertically down to targets at bottom of screen Response Phase (B) Participants reproduce the sequence using D/F/J/K keys Length of presented sequence is adaptive via staircase method 2 correct or incorrect leads to +1/-1 length for next sequence Experiment 1 (A): Presented fragments always start from the same point within the repeated sequence Two 50-minute training sessions; 20% repeated/80% random (N=40) Experiments 2 and 3 (B): Presented fragments start from randomized points within the repeated sequence Exp 2: Two 50-minute training sessions 20% repeated and 80% random (N=26) Exp 3: Two 50-minute training sessions 40% repeated and 60% random (N=21) D J F K J K D F J D K F 12-item repeating sequence D J F K J K D F J D K F 4-item fragment 5-item fragment 6-item fragment 4-item fragment 5-item fragment 6-item fragment Higher WM span Hebb repetition effect (supported by LTM) Enhanced WM on task Enhanced task performance A B However, in Exp 3, the repetition effect is observed only in participants able to recognize the repeated sequence during a post-training recognition task, F(19)=4.86, p <.05 Experimental results Hebb repetition effect: In Exp 1, where the repeated sequence was obvious to participants, the effect can be observed at adaptive sequence lengths in all participants, F(39)=10.61, p<.01 In Exp 2 and 3, where the repeated sequence was not obvious to participants, the effect is not observed across all participants Effect of LTM/awareness: In Exp 2, no participants were aware of the repeated sequence, as measured on a post-training test of recognition In Exp 3, a subset of participants identified the repeated sequence, and these participants only demonstrated the repetition effect, F(19)=4.86, p <.05 Additionally, higher initial WM span seems to lead to greater LTM awareness, as higher-span participants recognized the repeated sequence at post-training, t (10)=2.73, p <.03 * Exp 1: Same starting point for repeated sequence *