Date published: 12/1/2017

Memory and learning are central to every aspect of cognition and behavior and the main focus of my research.  In the lab I co-direct with Robert Bjork, we explore the symbiotic interactions between learning and forgetting that often—and unintuitively—foster an adaptive memory system.

Forgetting as an Enabler of Learning

If asked, most people would probably say that forgetting was their biggest memory problem.  Frequently, however, forgetting is exactly what we need to do to function efficiently.  To avoid disabling emotions or influences of dysfunctional relationships, for example, we may want to forget embarrassing or painful events in our past.  We also need to forget to contend with a complex and constantly changing world.  We need, for example, to remember where we parked our car this morning, rather than yesterday morning or a week ago, and we need to remember our current password, phone number, or address, not the ones we had when using a previous computer or before moving to our current location.  Forgetting also plays an important role in successful retrieval.  When, for example, we search our memories for some desired information—such as the name of the person currently greeting us—we engage in a type of “online forgetting” process that involves inhibiting or selecting against the many similar names of other people we know in order to arrive at the correct one for this person.  Furthermore, the same conditions that produce forgetting—say, delaying an opportunity to restudy or changing the environmental context—then enhance learning when that material is restudied. 

In our lab, in collaboration with graduate students, undergraduate students, and postdoctoral fellows, we have studied such types of goal-directed forgetting and shown that the mechanism underlying them takes the form of retrieval inhibition, not active erasure or over-writing.  Consequently, the information we intentionally forget in the updating process remains in memory and can be relearned more quickly (compared to learning it from scratch) should it become needed again.  Additionally, our study of the type of forgetting involved in the retrieval process led us to the discovery of the phenomenon now known in the literature as retrieval-induced forgetting (or RIF).  Retrieving information from our memories alters our memories, not only in the sense of making the retrieved information more recallable in the future, but also by making other information associated to the same cues less recallable in the future.  In our lab’s research on this phenomenon, which was predicted by our “new theory of disuse” (Bjork & Bjork, 1992), we have gathered considerable evidence that such retrieval dynamics reflect a selection-plus-suppression mechanism that is strength-independent and competition dependent—factors that support an inhibitory account of RIF.  The mechanisms underlying RIF, however, remain a focus of extensive research.

Using Desirable Difficulties to Enhance Learning

More recently, our lab has also been concerned with the issue of whether what we have learned in the lab about learning and memory can be applied to optimize both classroom instruction and self-directed learning.  Both as instructors and learners, we are susceptible to assuming that conditions of instruction that enhance performance during acquisition also enhance long-term learning.  Our research has shown that this assumption is often dramatically wrong.  Instead, manipulations that make performance improve rapidly during acquisition often fail to support long-term retention and transfer, whereas other manipulations that introduce difficulties, slowing the rate of apparent learning, can actually enhance retention and transfer.  Such manipulations, which we call desirable difficulties, include spacing (rather than massing) repeated study opportunities; interleaving (rather than blocking) practice on separate topics; varying (rather than keeping constant) the manner in which to-be-learned material is presented; providing intermittent (rather than continuous) feedback on performance; and using tests (rather than additional presentations) as learning events.  

We see the idea that difficulties can be desirable and the body of research on which that idea rests as providing a foundation for improving teaching as well as self-directed learning in potentially dramatic ways.  To enhance learning, we need to be challenged in multiple ways—ways that introduce variability, require generation, interleave topics, and tap into other desirable difficulties that require more active involvement in the learning process.  Achieving learning that supports retention and transfer requires producing the kind of elaborated and inter-linked memory representation that basic researchers have shown will sustain access to knowledge, retard forgetting, and enhance transfer.  Introducing desirable difficulties is one key to achieving that goal.  It is necessary, in short, for teachers and learners alike to become suspicious of a sense of ease and to be undeterred by a sense of difficulty.

My Path to Cognitive Psychology

My route to becoming a cognitive psychologist studying human learning and memory in the Psychology Department at UCLA was fairly circuitous.  My life began in China where my parents were medical missionaries, followed by living in numerous places owing to my father being in the Public Health Service, but eventually graduating with a degree in Mathematics from the University of Florida.  It was not until my senior year that I took my first psychology course, but I was so intrigued by the potential for research on human learning and memory and by the collaborative nature of research in psychology, that I eventually focused on the sub-field of mathematical psychology in graduate school at the University of Michigan where I received my Ph.D.