This paper presents a spreading-activation theory of human semantic processing, which can be applied to a wide range of recent experimental results. The theory is based on Quillian's theory of semantic memory search and semantic preparation, or priming. In conjunction with this, several of the miscondeptions concerning Qullian's theory are discussed. A number of additional assumptions are proposed for his theory in order to apply it to recent experiments. The present paper shows how the extended theory can account for results of several production experiments by Loftus, Juola and Atkinson's multiple-category experiment, Conrad's sentence-verification experiments, and several categorization experiments on the effect of semantic relatedness and typicality by Holyoak and Glass, Rips, Shoben, and Smith, and Rosch. The paper also provides a critique of the Smith, Shoben, and Rips model for categorization judgments.

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A total of 1,242 subjects, in five experiments plus a pilot study, saw a series of slides depicting a single auto-pedestrian accident. The purpose of these experiments was to investigate how information supplied after an event influences a witness's memory for that event. Subjects were exposed to either consistent, misleading, or irrelevant information after the accident event. Misleading information produced less accurate responding on both a yes-no and a two-alternative forced-choice recognition test. Further, misleading information had a larger impact if introduced just prior to a final test rather than immediately after the initial event. The effects of misleading information cannot be accounted for by a simple demand-characteristics explanation. Overall, the results suggest that information to which a witness is exposed after an event, whether that information is consistent or misleading, is integrated into the witness's memory of the event. Almost two centuries ago, Immanuel Kant (1781/1887) spoke of the human tendency to merge different experiences to form new concepts and ideas. That tendency has crucial implications for one's ability to report his or her experiences accurately. When one has witnessed an important event, such as a crime or an accident, one is occasionally exposed to subsequent information that can influence the memory of that event. This occurs even when the initial event is largely visual and the additional information is verbal in nature (Loftus, 1975; Pezdek, 1977). For instance, in a previous study, subjects saw films of complex fast-moving events such

The misinformation effect refers to the impairment in memory for the past that arises after exposure to misleading information. The phenomenon has been investigated for at least 30 years, as investigators have addressed a number of issues. These include the conditions under which people are especially susceptible to the negative impact of misinformation, and conversely when are they resistant. Warnings about the potential for misinformation sometimes work to inhibit its damaging effects, but only under limited circumstances. The misinformation effect has been observed in a variety of human and nonhuman species. And some groups of individuals are more susceptible than others. At a more theoretical level, investigators have explored the fate of the original memory traces after exposure to misinformation appears to have made them inaccessible. This review of the field ends with a brief discussion of the newer work involving misinformation that has explored the processes by which people come to believe falsely that they experienced rich complex events that never, in fact, occurred.In 2005 the journal Learning & Memory published the first experimental work using neuroimaging to reveal the underlying mechanisms of the "misinformation effect," a phenomenon that had captured the interest of memory researchers for over a quarter century (Okado and Stark 2005). These new investigators used a variation of the standard three-stage procedure typical in studies of misinformation. Their subjects first saw several complex events, for example one involving a man stealing a girl's wallet. Next some of the subjects got misinformation about the event, such as the fact that the girl's arm was hurt in the process (rather than her neck). Finally the subjects were asked to remember what they saw in the original event. Many claimed that they saw the misinformation details in the original event. For example, they remembered seeing the arm being hurt, not the neck. Overall, the misinformation was remembered as being part of the original event about 47% of the time. So, expectedly, a robust impairment of memory was produced by exposure to misinformationthe misinformation effect. But the researchers' new work had a twist: They went on to show that the neural activity that occurred while the subjects processed the events and later the misinformation predicted whether a misinformation effect would occur.In an essay that accompanied the Okado and Stark findings, I placed their results within the context of 30 years of research on behavioral aspects of the misinformation effect (Loftus 2005). Their work received much publicity, and boosted public interest in the misinformation effect as a scientific phenomenon. For example, WebMD (Hitti 2005) touted the new findings showing that brain scans can predict whether the memories would be accurate or would be infected with misinformation. And the Canadian press applauded the study as being the first to investigate how the brain encodes misinformation (Toronto Star 2005).So what do we know about the mi...

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Repression is one of the most haunting concepts in psychology. Something shocking happens, and the mind pushes it into some inaccessible corner of the unconscious. Later, the memory may emerge into consciousness. Repression is one of the foundation stones on which the structure of psychoanalysis rests. Recently there has been a rise in reported memories of childhood sexual abuse that were allegedly repressed for many years. With recent changes in legislation, people with recently unearthed memories are suing alleged perpetrators for events that happened 20, 30, even 40 or more years earlier. These new developments give rise to a number of questions: (a) How common is it for memories of child abuse to be repressed? (b) How are jurors and judges likely to react to these repressed memory claims? (c) When the memories surface, what are they like? and (d) How authentic are the memories?

For most of this century, experimental psychologists have been interested in how and why memory fails. As Greene2 has aptly noted, memories do not exist in a vacuum. Rather, they continually disrupt each other, through a mechanism that we call "interference." Literally thousands of studies have documented how our memories can be disrupted by things that we experienced earlier (proactive interference) or things that we experienced later (retroactive interference). Relatively modern research on interference theory has focused primarily on retroactive interference effects. After receipt of new information that is misleading in some way, people make errors when they report what they saw3. The new, post-event information often becomes incorporated into the recollection, supplementing or altering it, sometimes in dramatic ways. New information invades us, like a Trojan horse, precisely because we do not detect its influence. Understanding how we become tricked by revised data about a witnessed event is a central goal of this research. The paradigm for this research is simple. Participants first witness a complex event, such as a simulated violent crime or an automobile accident. Subsequently, half the participants receive new misleading information about the event. The other half do not get any misinformation. Finally, all participants attempt to recall the original event. In a typical example of a study using this paradigm, participants saw a video depicting a killing in a crowded town square. They then received written information about the killing, but some people were misled about what they saw. A critical blue vehicle, for instance, was referred to as being white. When later asked about their memory for the color of the vehicle, those given the phony information tended to adopt it as their memory; they said they saw white4. In these and many other experiments, people who had not received the phony information had much more accurate memories. In some experiments the deficits in memory performance following receipt of misinformation have been dramatic, with performance differences as large as 30 or 40%. This degree of distorted reporting has been found in scores of studies, involving a wide variety of materials. People have recalled nonexistent broken glass and tape recorders, a clean-shaven man as having a mustache, straight hair as curly, stop signs as yield signs, hammers as screwdrivers, and even something as large and conspicuous as a barn in a bucolic scene that contained no buildings at all. In short, misleading post-event information can alter a person's recollection in a powerful ways, even leading to the creation of false memories of objects that never in fact existed.

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