The Seven Sins of Memory: How the Mind Forgets and Remembers is a book by Daniel Schacter, former chair of Harvard University's Psychology Department and a leading memory researcher. The book revolves around the theory that "the seven sins of memory" are similar to the Seven deadly sins, and that if one tries to avoid committing these sins, it will help to improve one's ability to remember. Schacter argues that these features of human memory are not necessarily bad, and that they serve a useful purpose in memory. For instance, persistence is one of the sins of memory that can lead to things like post traumatic stress syndrome. However persistence is also necessary for long-term memory, and so it is essential. Overview Schacter asserts that "memory's malfunctions can be divided into seven fundamental transgressions or 'sins'." These are transience, absent-mindedness, blocking, misattribution, suggestibility, bias, and persistence. The first three are described as sins of omission, since the result is a failure to recall an idea, fact, or event. The other four sins (misattribution, suggestibility, bias, and persistence) are sins of commission, meaning that there is a form of memory present, but it is not of the desired fidelity or the desired fact, event, or ideas. Types of memory failure Transience Transience means the influence from one memory on another one. Failures are due to the general deterioration of a specific memory over time and are enhanced by interference of memories. There are two types of interference: proactive interference (old memory inhibits the ability to remember new memories properly), and retroactive interference (new memories inhibit the ability to remember old memories accurately). Typically, more information can be remembered of recent events than older events. This is especially true with episodic memory as compared to semantic memory, as "richly detailed evocative memories from the past" contain more multidimensional information than "general conceptual knowledge divested of a specific spatiotemporal context". Since memories of experiences contain multifaceted information—including sensory, spatial, and temporal details—, there are more areas inside an episodic memory susceptible to interference. One of Schacter's examples of transience is a study of how well undergraduates remembered how they found out about the O. J. Simpson trial verdict immediately after, 15 months, and 32 months later. After three years, fewer than 30 percent remembered accurately, and nearly half had major errors. Absent-mindedness This form of memory failure involves a problem at the point