Journal of Memory and Language 48 (2003) 195-206. doi:10.1016/S0749-596X(02)00524-7Received by publisher: 2001-11-26Harvest Date: 2016-01-04 12:22:46DOI: 10.1016/S0749-596X(02)00524-7Page Range: 195-20

If strategy shifts speed up performance, learning curves should show discontinuities where such shifts occur. Relatively smooth curves appear consistently in the literature, however. To explore this incongruity, we examined learning when multiple strategies were used. We plotted power law learning curves for aggregated data from four mental arithmetic experiments and then plotted similar curves separately for each participant and strategy. We then evaluated the fits achieved by each group of curves. In all four experiments, plotting separately by strategy produced significantly better fits to individual participants' data than did plotting a single power function. We conclude that improvement of solution time is better explained by practice on a strategy than by practice on a task, and that careful assessment of trial-by-trial changes in strategy can improve understanding of the effects of practice on learning. 0The generality and precision simultaneously achieved by expressing empirical regularities as mathematical functions facilitates theoretical development, testing, and the application of scientific knowledge. Although mathematical laws are more prevalent in the physical sciences than in the social sciences, psychology's search for quantitative laws that describe human behavior is long-standing, dating back to the 1850s. A few notable successes have been achieved, including Fitts's law (1954) and the Hick-Hyman law (Hick, 1952;Hyman, 1953). Newell and Rosenbloom (1981) proposed another candidate for the status of quantitative psychological law. They argued that the power law of practice 1 offers a sufficiently accurate, general, and useful characterization of human skill acquisition. This article examines that proposal in the light of empirical evidence that strategy changes sometimes play an important role in cognitive skill acquisition. Such evidence raises questions about the adequacy of the regular power law as a complete descriptor of the temporal course of complex human learning. Our goal is to describe the tension arising between the general formulation of the regular power law and the data on strategy shifts and then to suggest a way to reconcile the two bodies of evidence.It is well established that practice on a task almost always improves performance, both by reducing the number of errors and by reducing the time required to perform the task. Many longitudinal studies using performance time (e.g., solution time for problems, reaction time to stimuli) to measure skill acquisition have shown a remarkable regular-0.1. This regularity was first noted by Lewis (1976) in an unpublished manuscript that Newell acknowledged reading.

Abstract:Instructing people to forget a list of items often leads to better recall of subsequently studied lists (known as the benefits of directed forgetting). The authors have proposed that changes in study strategy are a central cause of the benefits (L. Sahakyan & P. F. Delaney, 2003). The authors address 2 results from the literature that are inconsistent with their strategy-based explanation: (a) the presence of benefits under incidental learning conditions and (b) the absence of benefits in recognition testing. Experiment 1 showed that incidental learning attenuated the benefits compared with intentional learning, as expected if a change of study strategy causes the benefits. Experiment 2 demonstrated benefits using recognition testing, albeit only when longer lists were used. Memory for source in directed forgetting was also explored using multinomial modeling. Results are discussed in terms of a 2-factor account of directed forgetting. Key words: directed forgetting, intentional forgetting, study strategies, multinomial modeling, inhibition Article:When people find out that they are talking to a memory specialist, they often ask about how to improve their memories and how to remember more effectively. The irony of this is that people should perhaps be interested in how to forget things better in order to improve memory, as it appears that forgetting often leads to better memory (R. A. Bjork, 1989).One way to study the linkage between forgetting and learning is to ask people to forget something they have just studied-a procedure known as directed forgetting. A forget instruction can be delivered either after each item (known as the item method) or after a block of items (known as the list method). These two methodologies were shown to have different underlying mechanisms, with the item method reflecting encoding phenomena (better encoding of forget vs. remember items), and the list method most likely reflecting retrieval phenomena (e.g., Basden, Basden, & Gargano, 1993;R. A. Bjork, 1989). The current article focuses on the list method of directed forgetting because the mechanism underlying this phenomenon has created a variety of theoretical viewpoints as opposed to the mechanism supporting the item method. (For a more complete review of directed forgetting and related procedures such as specific intentional forgetting, see H. Johnson, 1994, or MacLeod, 1998 A typical list method directed forgetting study presents participants with two word lists to study. Between administration of the two lists, the experimenter instructs half of the participants to forget the first list and the  We are grateful to Xiangen Hu and William Batchelder for their help with the GPT.EXE software and multinomial models in general. Thanks also go to Kathryn Hughes, Kristin Kukharenko, Ryan Lobo, and Isabel Manzano for their help in data collection and scoring.

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