Retrieval practice enhances the accessibility but not the quality of memory

Psychon Bull Rev (2016) 23:831–841 DOI 10.3758/s13423-015-0937-x BRIEF REPORT Retrieval practice enhances the accessibility but not the quality of memory David W. Sutterer 1,2 & Edward Awh 1,2,3 Published online: 24 September 2015 # Psychonomic Society, Inc. 2015 Abstract Numerous studies have demonstrated that retrieval from long-term memory (LTM) can enhance subsequent memory performance, a phenomenon labeled the retrieval practice effect. However, the almost exclusive reliance on categorical stimuli in this literature leaves open a basic question about the nature of this improvement in memory performance. It has not yet been determined whether retrieval practice improves the probability of successful memory retrieval or the quality of the retrieved representation. To answer this question, we conducted three experiments using a mixture modeling approach (Zhang & Luck, 2008) that provides a measure of both the probability of recall and the quality of the recalled memories. Subjects attempted to memorize the color of 400 unique shapes. After every 10 images were presented, subjects either recalled the last 10 colors (the retrieval practice condition) by clicking on a color wheel with each shape as a retrieval cue or they participated in a control condition that involved no further presentations (Experiment 1) or restudy of the 10 shape/color associations (Experiments 2 and 3). Performance Electronic supplementary material The online version of this article (doi:10.3758/s13423-015-0937-x) contains supplementary material, which is available to authorized users. * David W. Sutterer * Edward Awh 1 Department of Psychology, The University of Chicago, Chicago, IL, USA 2 The Institute for Mind and Biology, The University of Chicago, 940 E. 57th St., Chicago, IL 60637, USA 3 The Grossman Institute for Neuroscience, The University of Chicago, 940 E. 57th St., Chicago, IL 60637, USA in a subsequent delayed recall test revealed a robust retrieval practice effect. Subjects recalled a significantly higher proportion of items that they had previously retrieved relative to items that were untested or that they had restudied. Interestingly, retrieval practice did not elicit any improvement in the precision of the retrieved memories. The same empirical pattern also was observed following delays of greater than 24 hours. Thus, retrieval practice increases the probability of successful memory retrieval but does not improve memory quality. Keywords Cued recall . Memory . Mnemonic precision . Testing effect Introduction Numerous studies have demonstrated that retrieval from longterm memory (LTM) can enhance subsequent memory performance, a phenomenon labeled the retrieval practice effect (Carrier & Pashler, 1992). The benefits of retrieval practice have been observed with a wide variety of memoranda (Roediger & Karpicke, 2006), including word pairs (Pyc & Rawson, 2009), pictures (Wheeler & Roediger, 1992), and spatial positions (Carpenter & Pashler 2007; Rohrer, Taylor, and Sholar, 2010; Carpenter & Kelly, 2012). Varying explanations have been offered for how retrieval practice enhances memory performance. Some have focused on increased elaborative retrieval during testing (Carpenter, 2009), whereas others have emphasized the narrowing of the retrieval search space via helpful contextual associations (Lehman, Smith, and Karpicke, 2014). One common assumption of these accounts is that retrieval practice enhances the probability of access to a memory rather than the quality of the memory. This focus on accessibility over fidelity may be 832 attributable in part to the fact that past studies have typically used discrete word or picture stimuli (and all-or-none measures of accuracy) that do not allow clear measurements of memory fidelity. That said, some past findings may be consistent with a putative effect of retrieval practice on memory quality. For example, Chan and McDermott (2007) found that retrieval practice improved participants’ ability to avoid semantically similar lures during a recognition test and improved source memory. Likewise, Szpunar, McDermott, and Roediger (2008) found that testing improves list discrimination. However, while each of these findings could reflect a more precise memory (e.g., of specific semantic content, or of the temporal context associated with an item), the binary nature of the responses in these studies also allows for an interpretation based on retrieval probability. An approach that may provide more traction for understanding the effect of retrieval practice on the quality of item-specific memory is to allow participants to report remembered information along a continuous response space. For example, Carpenter and Kelly (2012) used a continuous response space in a task where subjects recalled the precise positions of different objects. Retrieval practice resulted in a decrease in the average response error for retrieved locations relative to restudied locations. However, although a change in memory quality provides an intuitive explanation of these findings, a reduced guessing rate in the retrieval practice condition also would yield lower average response errors. Thus, the goal of the present work was to examine the retrieval practice effect using an analytic approach that can estimate both the probability of retrieval and the quality of the retrieved representations. We measured performance in a shape/color recall task in which the possible colors were drawn from a continuous 360degree space, and we used a mixture-modeling approach (Zhang & Luck, 2008) that provided separate measures of the probability of recall and the quality of the retrieved memories. This analytic approach has been widely applied to the field of working memory (see Luck & Vogel, 2013 for review), and has recently been applied to the study of LTM (Brady et al., 2013). To anticipate our conclusions, retrieval practice elicited robust improvements in the probability of memory access, but absolutely no improvement in the fidelity of the retrieved memories. Experiment 1: Test versus no test Method Participants Twenty-two undergraduates at the University of Oregon completed the experiment for course credit. All participants gave Psychon Bull Rev (2016) 23:831–841 informed consent according to procedures approved by the University of Oregon institutional review board. Apparatus Stimuli were generated in MATLAB using Psychophysics Toolbox extension (Brainard, 1997; Pelli, 1997) and were presented on a 17-in. flat CRT computer screen (60-HZ refresh rate). The viewing distance was ~80 cm. Stimuli were 9.2° × 9.2° of visual angle. Stimuli Four hundred nameable pictures (e.g., animals, plants, shapes, countries, U.S. states, and symbols) were obtained via a web search for royalty free clip art. One of 360 continuous colors was assigned to each image, with different color/shape sets for each subject. Task and procedure The 400 stimuli were presented in two successive runs (...truncated)