The authors performed a meta-analysis of the distributed practice effect to illuminate the effects of temporal variables that have been neglected in previous reviews. This review found 839 assessments of distributed practice in 317 experiments located in 184 articles. Effects of spacing (consecutive massed presentations vs. spaced learning episodes) and lag (less spaced vs. more spaced learning episodes) were examined, as were expanding interstudy interval (ISI) effects. Analyses suggest that ISI and retention interval operate jointly to affect final-test retention; specifically, the ISI producing maximal retention increased as retention interval increased. Areas needing future research and theoretical implications are discussed.

Two influential models of recognition memory, the unequal-variance signal-detection model and a dual-process threshold/detection model, accurately describe the receiver operating characteristic, but only the latter model can provide estimates of recollection and familiarity. Such estimates often accord with those provided by the remember-know procedure, and both methods are now widely used in the neuroscience literature to identify the brain correlates of recollection and familiarity. However, in recent years, a substantial literature has accumulated directly contrasting the signal-detection model against the threshold/detection model, and that literature is almost unanimous in its endorsement of signal-detection theory. A dual-process version of signal-detection theory implies that individual recognition decisions are not process pure, and it suggests new ways to investigate the brain correlates of recognition memory.

Recognition memory is widely viewed as consisting of two components, recollection and familiarity, which have been proposed to be dependent on the hippocampus and the adjacent perirhinal cortex, respectively. Here, we propose an alternative perspective: we suggest that the methods traditionally used to separate recollection from familiarity instead separate strong memories from weak memories. A review of work with humans, monkeys and rodents finds evidence for familiarity signals (as well as recollection signals) in the hippocampus and recollection signals (as well as familiarity signals) in the perirhinal cortex. We also indicate ways in which the functions of the medial temporal lobe structures are different, and suggest that these structures work together in a cooperative and complementary way.Declarative memory refers to the capacity to consciously remember the past and depends on the integrity of the medial temporal lobe (comprising the hippocampus, the dentate gyrus and the subicular complex, together with the entorhinal, perirhinal and parahippocampal cortices, which lie along the adjacent parahippocampal gyrus). One of the most widely studied examples of declarative memory is recognition -the ability to judge a recently encountered item as having been presented previously. Recognition memory is widely viewed as consisting of two components: recollection and familiarity 1,2 . Recollection involves remembering specific contextual details about a prior learning episode; familiarity involves simply knowing that an item was presented, without having available any additional information about the learning episode.Interest in this distinction greatly increased when Brown and Aggleton 3 proposed a neuroanatomical basis for these two processes. Their proposal was that recollection depends on the hippocampus, whereas familiarity depends on the adjacent perirhinal cortex. Since that time, others have elaborated on this idea 4-6 , and it has become the basis for the design and analysis of a good deal of experimental work. However, alternative formulations have also been advanced about the nature of recognition memory and its anatomical foundations 7,8 , and a consensus has not yet emerged.Correspondence to L.R.S. e-mail: lsquire@ucsd.edu. NIH Public Access Author ManuscriptNat Rev Neurosci. Author manuscript; available in PMC 2008 April 21. Published in final edited form as:Nat Rev Neurosci. 2007 November ; 8(11): 872-883. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptHere, we review studies of humans, monkeys and rodents that have investigated the functional organization of the medial temporal lobe using a variety of methods: lesions, single-unit activity and neuroimaging. The general organizational principles of the medial temporal lobe are similar in these species 9 , and it is reasonable to suppose that what is learned about medial temporal lobe function in one species has relevance to the others. Although many of the studies have been interpreted as providing support for the n...

Traditional theories of forgetting are wedded to the notion that cue-overload interference procedures (often involving the A-B, A-C list-learning paradigm) capture the most important elements of forgetting in everyday life. However, findings from a century of work in psychology, psychopharmacology, and neuroscience converge on the notion that such procedures may pertain mainly to forgetting in the laboratory and that everyday forgetting is attributable to an altogether different form of interference. According to this idea, recently formed memories that have not yet had a chance to consolidate are vulnerable to the interfering force of mental activity and memory formation (even if the interfering activity is not similar to the previously learned material). This account helps to explain why sleep, alcohol, and benzodiazepines all improve memory for a recently learned list, and it is consistent with recent work on the variables that affect the induction and maintenance of long-term potentiation in the hippocampus.

SummaryThe U.S. legal system increasingly accepts the idea that the confidence expressed by an eyewitness who identified a suspect from a lineup provides little information as to the accuracy of that identification. There was a time when this pessimistic assessment was entirely reasonable because of the questionable eyewitness-identification procedures that police commonly employed. However, after more than 30 years of eyewitness-identification research, our understanding of how to properly conduct a lineup has evolved considerably, and the time seems ripe to ask how eyewitness confidence informs accuracy under more pristine testing conditions (e.g., initial, uncontaminated memory tests using fair lineups, with no lineup administrator influence, and with an immediate confidence statement). Under those conditions, mock-crime studies and police department field studies have consistently shown that, for adults, (a) confidence and accuracy are strongly related and (b) high-confidence suspect identifications are remarkably accurate. However, when certain non-pristine testing conditions prevail (e.g., when unfair lineups are used), the accuracy of even a high-confidence suspect ID is seriously compromised. Unfortunately, some jurisdictions have not yet made reforms that would create pristine testing conditions and, hence, our conclusions about the reliability of high-confidence identifications cannot yet be applied to those jurisdictions. However, understanding the information value of eyewitness confidence under pristine testing conditions can help the criminal justice system to simultaneously achieve both of its main objectives: to exonerate the innocent (by better appreciating that initial, low-confidence suspect identifications are error prone) and to convict the guilty (by better appreciating that initial, high-confidence suspect identifications are surprisingly accurate under proper testing conditions).

Work with patient H.M., beginning in the 1950s, established key principles about the organization of memory that inspired decades of experimental work. Since H.M., the study of human memory and its disorders has continued to yield new insights and to improve understanding of the structure and organization of memory. Here we review this work with emphasis on the neuroanatomy of medial temporal lobe and diencephalic structures important for memory, multiple memory systems, visual perception, immediate memory, memory consolidation, the locus of long-term memory storage, the concepts of recollection and familiarity, and the question of how different medial temporal lobe structures may contribute differently to memory functions.

I. It should be noted that the power and logarithmic functions, both of which assume that dyldt is an inverse function of time, are undefined at a retention interval of zero. In practice, if a retention interval of zero were employed, some modification of these functions would be needed.For example, the power function might be written as a(t + I)-b, which is defined, at t = 0 and quickly begins to approximate at -b as t increases. tion appeared to be logarithmic in form. More recently, Wickelgren found that forgetting functions produced by verbal recognition procedures were accurately described either by an exponential-power function (Wickelgren, 1972(Wickelgren, , 1974 or by a simple power function (Wickelgren, 1977). In the animal memory literature, White (1985) has repeatedly found that the simple exponential provides an acceptable fit to forgetting functions produced by the delayed matching-to-sample (DMTS) task. Harnett, McCarthy, and Davison (1984), however, suggested that the hyperbola seems to provide a more accurate description of forgetting on this task. Table 1 lists the mathematical functions that have, at one time or another, been taken to represent the course of forgetting. For comparative purposes, the table also includes the equation for a straight line. As shown in the rightmost column, linear decay implies that the rate of change in the strength of the memory trace with respect to time, dyldt, is constant. The second function, exponential decay, implies that the rate of forgetting slows as the strength of the memory trace declines (Le., dy/dt is a constant proportion of y). The third function, hyperbolic decay, implies that the rate of forgetting decreases in proportion to the square of memory strength. The last three functions (logarithmic, power, and exponential-power) all imply, in one way or another, that the rate of forgetting is retarded by the passage of time. This property captures the essence of Wickelgren's (1972, 1974) trace-resistance theory of decay and is consistent with Jost's second law: "Given two associations of the same strength, but of different ages, the older falls off less rapidly in a given length of time" (Hovland, 1951). 1 The question under consideration here is wheth~r one of the functions shown in Table 1 can consistently provide the Table 1. Forgetting function candidates Abstract-Almost everyone would agree that the course offorgetting is some curvilinear function oftime. The purpose ofthe research described herein was to identify the nature of that function. Three experiments are reported, two involving human subjects and one involving pigeons. The human experimellts investigated this issue using recall of words and recognition of faces, whereas the pigeon experimellt employed the standard delayed matching-to-sample task. In all cases, the course of forgetting was best described by a simple power function of time relative to five other reasonable alternatives (linear, exponelltial, exponential-power, hyperbolic, and logarithmic). Furthermore, a reanalysis of E...

A mirror effect can be produced by manipulating word class (e.g., high vs. low frequency) or by manipulating strength (e.g., short vs. long study time). The results of 5 experiments reported here suggest that a strength-based mirror effect is caused by a shift in the location of the decision criterion, whereas a frequency-based mirror effect occurs although the criterion remains fixed with respect to word frequency. Evidence supporting these claims is provided by a series of studies in which high frequency (HF) words were differentially strengthened (and sometimes differentially colored) during list presentation. That manipulation increased the HF hit rate above that for low frequency (LF) words without selectively decreasing the HF false alarm rate, just as a fixed-criterion account of the word-frequency mirror effect predicts.In recent years, a well-known empirical regularity known as the mirror effect has commanded a great deal of attention. The mirror effect refers to the relationship between hit and false alarm rates in two conditions associated with different levels of recognition accuracy. Specifically, a mirror effect is said to exist when the condition associated with more accurate recognition performance is characterized by both a higher hit rate and a lower false alarm rate than the less accurate condition. This effect is so reliably observed that Glanzer, Adams, Iverson, and Kim (1993) described it as a "regularity of recognition memory."The mirror effect can be produced by manipulating either the class or the strength of the items presented for study. The most common class manipulation is based on word frequency (high vs. low), whereas strength is usually manipulated by varying study time or number of item presentations. The consistency of the mirror effect across different methods of manipulating recognition accuracy suggests the influence of a single underlying mechanism. In terms of signal detection theory, that mechanism is often thought to be a shift in the criterion for deciding whether to respond "yes" or "no" to a test item. Figure 1 illustrates the criterion-shift argument for a strength manipulation using the standard assumptions of signal detection theory. This model assumes that the decision axis represents a strength-of-evidence variable, such as familiarity. According to this account, the familiarity values associated with the target items and lure items are both normally distributed, with the mean of the target distribution Strength-Based Mirror Effects