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A short review of the human memory and its processes

Abstract Research on human memory has increased significantly in the last few decades.

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Inconsistencies and controversies inherent to such research, however, are rarely articulated on published reports. The goal of the present article is to present and discuss a series of open questions related to major topics on human memory research that can be addressed by future research.

The topics covered here are visual working memory, recognition memory, emotion and memory interaction, and methodological issues of false memories studies.

Overall, the present work reveals a series of open questions and alternative analysis which could be useful for the process of hypothesis generation, and consequently for the design and implementation of future research on human memory. Such intense proliferation, however, may paradoxically overshadow some unanswered questions in the field of memory research. While this increase in volume of research may supply interested readers with an abundance of data and results, it may not necessarily be helpful in terms of revealing for him or her the main controversies and inconsistencies in the field.

Thus, our goal in this paper is to discuss some hypotheses that we consider central to the advance of the study of human memory from a cognitive psychology perspective. Instead of focusing on new data, we pursued to reveal a set of controversies and open questions in the field of human memory research.

Such controversies and open questions, we believe, may be useful as bases for generating hypothesis for future research McGuire, 1997. The first controversy we approach concerns current theories of visual working memory. We discuss unexpected effects in visual working memory tasks apparently generated by task-irrelevant visual information Logie, 1995 ; 2011.

That is, task-irrelevant visual information causes deleterious effects on working memory capacities for information that cannot be semantically encoded. Stimuli that can be semantically encoded, on the other hand, tend to be more resistant to such visual interference. This finding, nonetheless, is not consistently replicated, and characteristics of task and stimulus may underlie such inconsistency.

Human memory retention and recall processes. A review of EEG and fMRI studies.

Thus, we suggest that an important approach for future research a short review of the human memory and its processes to identify stimuli dimensions that can be determinant to make such short-term visual representations either resistant or susceptible to irrelevant visual inputs.

Another topic concerns the debate about single- versus dual-process theories of recognition memory Wixted, 2007 ; Yonelinas, 2002. To study recognition memory, researchers usually let participants encode a set of items i. According to single-process theories, such discrimination process is based primarily on a strength-like signal of familiarity, whereas according to dual-process theories, such discrimination is typically based on a combination of familiarity signal with additional contextual and detailed episodic information.

These conflicting approaches provide different predictions regarding behavioral performance, and we discuss the potential corroboration or refutation of such predictions by experimental findings. We discuss several unresolved issues concerning the interaction between emotion and memory in the section Emotion and Memory Accuracy of the present article.

We discuss first the parallel increase in memory accuracy for central and decrease for peripheral details of emotional events Pickel, 2007 ; a phenomenon often termed "weapon focus effect". Although several studies have shown that emotional information is more memorable than neutral information Hamann, 2001the former also appears to be more susceptible to distortion. Another important topic discussed in the referred section, is the methodological limitations of extant studies investigating the interaction between memory and emotion.

Such methodological limitations should be carefully approached by future research. In this section, we also approach predictions concerning the influence of emotion on false memories based on the Fuzzy-Trace Theory, emphasizing its theoretical relevance for further research.

  1. Theories and debate in visuo-spatial working memory.
  2. Another topic concerns the debate about single- versus dual-process theories of recognition memory Wixted, 2007 ; Yonelinas, 2002. Such investigations can focus on analysis of RT distributions for different types of tests, focus on the study of processing types serial x parallel, e.
  3. Nature Reviews Neuroscience, 7, 54-64. Pragmatics of measuring recognition memory.

Finally, we consider current data analysis approaches to false memory, and suggest that systematic analysis of reaction times could be a successful approach for future research. Balota and Yap 2011 have already shown that reaction time analysis could have the potential of bringing relevant advances for the field. In sum, we approach several topics on memory research in the following sections. In contrast to a typical review article, however, these topics are discussed in terms of their unanswered questions, inconsistencies, and controversial issues.

We expect that the discussion of such issues motivate the generation of new hypothesis for future research, and consequently help to advance the comprehension of human memory. Working Memory and Irrelevant Visual Input The visual working memory construct VWMas proposed by Logie 1995contains two structures, the visual cache and the inner scribe.

The visual cache, or visual short-term store, stores visual representations, as color and shape of stimuli. The inner scribe, on the other hand, stores spatial information and is responsible for the rehearsal of the visuo-spatial content stored in the visual cache. Unlike the phonological memory model, however, visual sensory information cannot reach the visual cache directly Logie, 2011.

Representations stored in the visual cache are acquired through vision, tactile or verbal descriptions of environmental scenes, and interpreted according to long-term based knowledge. These representations contain, in abstract form, the necessary information to reconstruct visual mental images that can be inspected and manipulated consciously. The proposal that visual information reaches the visual cache indirectly has been put into question in theoretical grounds Baddeley, 2007 ; Pearson, 2001 ; Quinn, 20082012 and in experimental studies using irrelevant visual input techniques.

One such technique, the Dynamic Visual Noise DVNconsists in a flickering black and white dot pattern similar to that produced by a TV screen out of tune.

It impairs performance in memory tasks wherein mental images are created from verbal instructions pegword. The DVN also impairs memory performance when stimuli are presented visually, although the effect of noise is less consistent in this case. The simplest account for differences of DVN effects on memory and visual image tasks is methodological.

In visual image tasks, presentation of DVN and generation of mental images are simultaneous. Assuming that perception and generation of mental images activate overlapping brain regions, as proposed by Kosslyn 1994the impairment caused by the presentation of DVN can result from the interference of irrelevant perceptual information during the generation of mental images.

In visual memory tasks, the DVN is presented after stimuli have been moved from perception to a more stable representation, possibly in the short-term visual memory.

Methodological differences in visual image and visual memory tasks may explain the difference between effects of DVN in these two types of task. However, it does not explain why DVN impairs recognition of some types of stimuli, while leaving others unaffected. Differences between effects of DVN on memory tasks with more complex stimuli, such as Chinese characters or geometric patterns Andrade et al.

Quinn 2012 suggests that different systems may be involved in the storage of these two broad types of stimuli. Complex stimuli, such as Chinese characters and visual patterns, are easier to encode semantically, whereas stimuli involving subtle variations in size, color, and shape, remain for longer in a pre-semantic visual store, which is more susceptible to interference from sensory or perceptual information.

Orme 2009who showed that more easily nameable visual patterns are less sensitive to the effect of the DVN, obtained evidence that corroborates this assumption. Such issues could be investigated by future research by assessing the amount of details required to impair the maintenance of graphical fonts and Chinese characters Andrade et al.

In sum, even though some studies attribute the variable effects of DVN to rehearsal or to generation processes involved in the maintenance of memorized representations on consciousness Darling et al. Thus, the identification of stimuli dimensions that determine whether visual representations are affected by irrelevant visual input is an important goal for future research. Findings from such studies could extend our knowledge regarding visual short-term memory, as well as regarding the connection of such process to the visual buffer.

Single Versus Dual-process Models In typical recognition memory tasks, individuals are asked to discriminate previously encoded items from novel items. Such tasks usually a short review of the human memory and its processes an encoding phase wherein lists of items are presented to volunteers, and a test phase wherein items presented at the encoding phase are presented again, intermixed with novel items. During the test phase, participants judge whether each item has been previously encountered at the encoding phase or not.

There are currently two divergent theoretical views regarding the cognitive processes engaged during recognition memory tasks. According to the 'dual process' view, on the other hand, recognition memory involves a combination of familiarity processes and retrieval of contextual or qualitative details linked to each item, a process termed 'recollection' Mandler, 1980 ; Yonelinas, 2002.

In this section, we discuss arguments in favor and against each of these models, while highlighting some topics that can be further explored by future research. As can be seen in Figure 1Aaccording to the original signal detection framework, memory strength can be represented by a continuous horizontal axis in which information more to the left of the axis have a less intense memory signal i.

Thus, in recognition memory tests, 'old' and 'new' items can be described by two Gaussian distributions Figure 1Awith the distribution to the left representing new items and the one to the right old items. On panels A and B, horizontal arrows represent strength of memory evidence. The curves represent the distribution of memory signal from new and old items, and the vertical lines represent criterion.

Since its initial proposal as a short review of the human memory and its processes framework to account for recognition memory, SDT was adopted by several memory theorists as the framework of choice for characterizing this phenomenon e. The main reason for this is perhaps the elegance and parsimony of the model, its consistency with a number of theories of memory e. The question remains, however, of whether this model can be regarded as a true theoretical description of the process of recognition memory instead of just a pragmatic framework to measure memory performance.

Note that if one assumes that this model is a true description of recognition memory, one must assume also that recognition memory is based solely on familiarity processes. Therefore, the chief question here is whether the process of familiarity is enough to account for the phenomenon of recognition memory or not. Even though findings from recognition memory experiments are roughly consistent with the traditional SDT framework, subtle inconsistencies advanced by later memory researchers exposed a number of limitations inherent to single process models of recognition Yonelinas, 1994.

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Such pattern suggests that high confidence responses to encoded items are often accompanied by explicit retrieval of vivid contextual details, indicating the presence of recollective processes during their recognition. ROCs can be derived from recognition memory experiments in which participants rate their confidence on each of their responses i.

Thus, in panels A and B, the bottom left point in the graph represents the proportion of high confidence "old" responses for both actual old items hits - y-axis and for new items false alarms - x-axis. The following point second from left to rightrepresents the proportion of medium confidence "old" responses for both old items hits and new items false alarms.

The third, forth, and fifth points from left to right represent the proportions of low confidence "old", low confidence "new" and medium confidence "new" responses for actual old and new items respectively. It is important to note that these proportions are cumulative, thus the second point from left to right, for example, is the proportion of medium confidence "old" responses plus the proportion of high confidence "old" responses; the third point is the proportion of low confidence "old" plus the proportions of medium and high confidence "old" responses, and so on.

Notably, the proportion of high confidence "old" responses for actual old items hits is higher in panel B than in panel A, while the proportion of high confidence "old" responses to new items false alarms are equivalent in both panels. Such increased proportion of high confidence for hits generates an asymmetry in the ROC curve panel Band is interpreted by dual process theorists as resulting from recollective processes restricted to high confidence old responses.

These findings have instigated a heated debate between proponents of single and dual-process models of recognition memory, a debate that does not seem to become resolved anytime in the near future.

  • Memory and Cognition, 40 3 , 360-372;
  • Cognitive mechanisms of visual memories and visual images;
  • It is often also described as the process of memory, but I have used this description for the processes of encoding , consolidation , storage and recall in the separate Memory Processes section.

Researchers favorable to single process models have proposed adjustments to the original models in order to account for the ROCs asymmetries highlighted by Yonelinas 1994. Perhaps the most accepted updated single process model is the unequal variance signal detection model proposed by Mickes, Wixted and Wais 2007. According to this model, the distributions of novel and encoded items have different variances at test see Figure 1B. Even though this modified version of the original signal detection model is capable of account statistically for the aforementioned ROC asymmetries, it is not clear what this difference in variance means psychologically.

One could suggest that 'old' items are encoded with variable strength, becoming items with variable memory strength at test Jang, Mickes, Wixted, 2012 ; Wixted, 2007.

It is not clear, nonetheless, why novel items should not exhibit the same pattern. Note that as well as encoded items, novel items in typical recognition memory tests are common pieces of information i.

So, were not novel items supposed to be variable as well? Furthermore, in typical recognition tests old items were all encountered recently in an encoding list, while new items were encountered for the last time in different moments and contexts in each participant's natural environment. Then, would it not be more reasonable to expect the opposite of the pattern proposed by Wixted 2007?

That is, novel items imbued with a more variable memory signal than old items. This issue is in need of further research, which could be determinant to reveal the process or processes engaged during recognition memory. The question under debate is simple. How many cognitive processes people engage during recognition memory? Despite its simplicity, future studies should approach this question properly. An undesired but often widespread practice in psychological research is the reification of poorly defined mental constructs.

Otherwise, researchers risk assigning brain activations to mental constructs that have theoretical weaknesses in their most basic assumptions. Novel experimental paradigms pursuing to dissociate processes of familiarity and recollection during recognition tasks may be a useful approach to investigate this issue.

The remember-know paradigm, for example, have been used for several years to investigate these processes Tulving, 1985.