There are several theories in psychology about the mechanisms of forgetting. One, developed by Edward Thorndike in the early 20thcentury, is called “decay theory.” According to Thorndike, new information creates a neurochemical trace that will disintegrate over time if the idea is not actively rehearsed.
In this Mishna, Rabbi Dostai, in the name of Rabbi Meir, highlights the challenge of forgetting;
Whoever forgets even a single word of his learning is considered as if he has forfeited his life, as it is stated, “Just be careful, and diligently guard your soul, lest you forget the things that your eyes have seen” (Deut. 4:9). One might think that this applies also to one who [has forgotten because] his studies proved too difficult for him, therefore the verse continues, “that they do not fade from your mind as long as you live.” Thus, one does not forfeit his life unless he deliberately removes them from his heart.
Memory is essential for successful Torah learning and Jewish continuity. The consequences of failing to remember are dire. Yet, Rabbi Dostai also acknowledges the fact that forgetting is natural, and is sometimes excusable. What are the exact parameters of “his studies proved too difficult for him,” which removes culpability, and he “deliberately removes them from his heart,” which incurs liability? The commentaries offer several approaches, yielding different insights about memory and forgetting.
Most commentators assume that the Mishna is not addressing someone who deliberately and actively tries to forget Torah, as that is too obvious a violation to even mention. Rather, the deliberate removing Torah from one’s heart recited in the Mishna includes not reviewing one’s studies out of laziness (Tosafot Yom Tov). If one does review sufficiently and still does not remember, however, that is beyond his or her control. Another factor that negatively impacts memory is not properly understanding the material at the outset. When the information is not encoded properly, later retrieval is unlikely. If someone tried to process the information with appropriate learning techniques, but due to lack of full understanding is unable to later remember that information, that would fall under the exemption of “his studies proved too difficult for him” (see Rashi).
Others point to a possible motivational barrier to memory that stems from a lack of valuing Torah. As Rabbi Dr. Reuven Bulka writes, “one who forgets obviously has not approached Torah seriously enough, has not seen Torah, as so crucial that every word is critical, and therefore, should be vibrantly remembered.” The assumption is that if we truly cared, we would have a better chance of remembering. To the extent that our forgetting is rooted in lack of proper appreciation of Torah, we would be culpable.
Another factor that impacts our memory of Torah is how busy we are with non-Torah endeavors. One of the other theories of forgetting in psychology is interference, namely, the phenomenon wherein other information gets in the way from proper encoding or retrieval of information. To the extent that we don’t have a choice and must be involved with other pursuits like earning a livelihood or performing other mitzvot or responsibilities, presumably that would fall under” his studies proved too difficult for him” category. However, as Meiri points out, there are many endeavors we spend our time engaging in that are not necessary, and those do not avail us of an excuse to forget our learning.
It seems clear that in order to avail ourselves of the excuse “his studies proved too difficult for him,” we first need to put in proper effort. Rabbi Yosef Hayyun uses the Mishna as a springboard to discuss several strategies to enhance our capacity to remember, and would likely be necessary before justifying forgetting. First, he points to a strategy offered by many other commentators: constant and consistent review of material (chazara). He relates a story about a sage who reviewed a new teaching 40 times (Pesachim 72a) and adds the precedent of Rabbi Chiyya who would review his learning every 30 days (Berachot 38b). These models of reviewing map well onto current research in memory. In their book Made to Stick: The Science of Successful Learning, Peter Brown, Henry Roediger, and Mark MacDaniel highlight the importance of the effortful retrieval of previously learned information. Not only is repeated review important, but also delayed retrieval is essential. This entails recalling information after time has passed, which is an even more potent strategy, because the mental effort of retrieving the information helps strengthen the memories.
Another idea that Rabbi Hayyun suggests that similarly has both Talmudic precedent and corroboration from recent research, is verbally articulating out loud what we are learning (Eiruvin 53b-54a). In 2010, Colin Macleod and colleagues studied the impact of what they deemed the “production effect,” demonstrating that when materials are read aloud, it leads to substantial memory improvement as compared to silent reading. Additionally, Rabbi Hayyun encourages teaching others as an effective way to improve memory. The impact of teaching for a teacher’s own learning success is well documented as the protégé effect (Bargh & Schul, 1980), and one possible mechanism for the improvements in learning is due to improved memory that the process of teaching affords (Koh, Lee, and Lim, 2018).
While it is true that forgetting is natural and it is sometimes beyond our control, Rabbi Dostai reminds us that we need to do everything within our control to remember the essential ideas we encounter while learning Torah. We need to overcome laziness, value the content, learn the information clearly, review using proven retrieval practices, and use other techniques that will help us remember including reciting aloud, teaching to others, and any other strategy that proves effective. By putting in the effort to remember, may we merit the inverse of the cautionary warning of the Mishna, and instead be granted a long and prosperous life filled with meaningful messages from the Torah and the sages.