The effect of presentation format and encoding strategy on associative memory distortion

IntroductionPrevious studies using semantically related words revealed more accurate memory when the items were encoded visually rather than auditorily and when mental images were created during encoding. However, how the level of memory distortion is affected by the creation of different mental imagery formats or by techniques that should suppress generation of mental images has rarely been investigated.ObjectiveThe aim of the present studies was to investigate the ways in which the encoding strategy affects the accuracy of memory reports for two presentation formats of semantically related words: verbal and pictorial.MethodIn experiment 1, the participants were asked to memorize either pictures or their verbal equivalents (words) from the same category, using one of two encoding strategies: uttering the words or counting backwards. In experiment 2, pictorially or auditory presented material was encoded together with the creation of either visual or auditory mental images of the items. The results of the experimental groups were compared to control groups that received no specific instruction.ResultsHigher levels of false recognition, together with lower rates of correct recognition, were observed for words, presented either visually or auditory, relative to pictures. Moreover, self-generation of additional code during the processing of information favored the reduction of false recognitions.ConclusionEncoding strategies that engaged dual coding reduced false recognition. The results are discussed within the distinctiveness heuristic phenomenon.     

Time course of item and associative information: implications for global memory models

The time course of availability of associative and item information was examined by using a response signal procedure. Associative information discriminates between a studied pair of words and a pair with words from two different studied pairs. Item information is sufficient to discriminate between a studied pair and a pair not studied. In two experiments, discriminations that require associative information are delayed relative to those based on item information. Two additional experiments discount alternative explanations in terms of the time to encode the test items or task strategies. Examination of the global memory models of Gillund and Shiffrin (1984), Hintzman (1988), and Murdock (1982) shows that the models treat item and associative information inseparably. Modifications to these models which can produce separate contributions for item and associative information do not predict any difference in their availability. Two possible mechanisms for the delayed availability of associative information are considered: the involvement of recall in recognition and the time required to form a compound cue.     

Judgments of associative memory

Judgments of associative memory (JAM) were indexed by ratings given to pairs of cue and response words. The normed probabilities, p(response|cue), were obtained from free association norms. The ratings were linearly related to the probabilities. The JAM functions were characterized by high intercepts ( approximately 50 on a 100 point scale) and shallow slopes (<0.5). The JAM function generalized across materials and method of rating. The function was not affected by expectancies or semantic similarity. Attempts to alter the function by making alternative responses more available were unsuccessful. A computer simulation model (MINERVA 2) exhibited the linear JAM function and successfully accounted for more complex phenomena (like the joint influence of forward and backward associative strengths on ratings). The shallow JAM slope appears to result from a fundamental lack of discrimination among associative strengths. The high intercept appears to result partly from an independent post-mnemonic source of bias producing over-estimation of association.     

Single-item memory, associative memory, and the human hippocampus

We tested recognition memory for items and associations in memory-impaired patients with bilateral lesions thought to be limited to the hippocampal region. In Experiment 1 (Combined memory test), participants studied words and then took a memory test in which studied words, new words, studied word pairs, and recombined word pairs were presented in a mixed order. In Experiment 2 (Separated memory test), participants studied single words and then took a memory test involving studied word and new words. In a separate test, they studied word pairs and then took a memory test involving studied word pairs and recombined word pairs. In both experiments, patients were impaired at memory for single items as well as memory for associations, suggesting that the hippocampus is important for both of these memory functions. In Experiment 1, patients appeared to be more impaired at associative memory than item memory. In Experiment 2, patients were similarly impaired at associative memory and item memory. These different findings are considered, including the fact that in Experiment 1 the results depended on the fact that controls produced unexpectedly low false-alarm rates to recombined pairs. We discuss single-item and associative memory from the perspective that the hippocampus and adjacent cortex work cooperatively to signal recognition and that simple dichotomies do not adequately describe the division of labor within the medial temporal lobe.     

Imagery and associative memory in children

Second and sixth graders, ages 7–8 and 11–12, respectively, were presented with lists of pairs of nouns. They were asked to represent each pair in memory as a single interactive image, as two separate images, or by a control procedure. After presentation of the pairs, the children were tested either by cued or noncued recall. The difference between the interaction condition and the other conditions appeared in recall measures which reflect pairwise organization in memory (cued recall, pair recall, conditional recall probabilities, and χ²) to a much greater extent than in measures of individual item recall. The results were interpreted as supporting an imagery-organization hypothesis.     

On the flexibility and the fallibility of associative memory

We report the results of four experiments in which we explored the flexibility and fallibility of associative recognition memory. In each experiment, pairs were studied one or more times, and the task was to discriminate intact from rearranged pairs. The critical findings are that the pattern of false alarm rates was dependent on the nature of the recognition procedure (e.g., ratings vs. yes-no) and the situation in which the task was performed. The specific pattern of findings suggest that subjects adopt different recognition strategies in order to achieve a desired level of performance in the most efficient manner possible by varying the degree to which they base their decisions on familiarity versus recollected information. Implications for theories of recognition memory are discussed.     

Same face,same place,different memory: manner of presentation modulates the associative deficit in older adults

One of the more severe and consequential memory impairments experienced by older adults is the loss of the ability to form and remember associations. Although the associative deficit is often assumed to be unitary, memory episodes may contain different types of associations (e.g., item–item, item–context). Research in younger adults suggests that these different association types may involve different neural mechanisms. This raises the possibility that different association types are not equally affected by aging. In order to investigate this, the current study directly compared memory across item–item and item–context associations in younger and older adults by manipulating the manner of presentation of the associations. Results indicate that the associative deficit in aging is not uniform and that aging has a greater impact on item–context compared to item–item associations. The results have implications for theories of associative memory, age-related cognitive decline, and the functional organization of the medial temporal lobe in aging.     

Associative and categorical relations in the associative memory illusion

What kinds of associations underlie the associative memory illusion? In Experiment 1, lists composed of horizontal, or coordinate, free associates elicited false recognition of critical lures much more often than did lists composed of vertical, or subordinate, category instances. Experiment 2 replicated this result, and showed that the difference between free associates and category instances was not an artifact of differential levels of forward or backward associative strength. Associative structure plays an important role in the associative memory illusion: The illusion is strongest when the critical lure lies at the same level of categorization as the studied items.     

Structure and strategy in the associative false memory paradigm

List-learning experiments can have several levels of structure: individual words, the gist (if any) of each list, and the task in which those lists are embedded. The usual presentation of the DRM associative paradigm (Deese, 1959; Roediger & McDermott, 1995) strongly encourages a focus on gist and produces a high rate of false recall of key words (FRK). The experiments reported here were designed to invite the use of memory strategies based on structures other than the gist and thus reduce FRK. The crucial condition of Experiment 1, short lists followed by rehearsal, encouraged a focus on individual words and produced a low rate of FRK. In Experiment 2, the lists were embedded in a guessing game, which virtually eliminated FRK. FRK was also low in Experiments 3a and 3b when participants engaged in a complex task involving the first letters of list words. The relevance of these findings to false memories in the DRM and the connection of false autobiographical memories is discussed.     

Acoustic and associative coding in short-term memory

Short lists of word-digit pairs were presented to 456 college student subjects. One of the words was repeated as a memory probe either immediately after list presentation or after a short rehearsal interval. The stimulus words were either acoustically identical or associatively related (UP, DOWN). Both acoustic identity and associative relatedness produced a memory decrement which decreased with rehearsal. One interpretation of these results is that the primary memory trace is a multiple-dimension one and that, given time, subjects can recover non-acoustic information from it. The data also indicate that the “fate” over time is different for acoustically similar and associatively related items.     

Simple and associative recognition memory in the hippocampal region

Although it is well established that the hippocampal region is involved in the formation of declarative memory, the exact nature of its involvement is unclear. One view is that the hippocampal region is involved only in tasks that require the formation or use of associations. According to this view, the hippocampal region is not involved in traditional tests of recognition memory. An alternative view is that the hippocampal region combines and extends the processing carried out by structures in the parahippocampal gyrus and that it is involved in all forms of declarative memory, including recognition memory. Using event-related functional magnetic resonance imaging (fMRI), we observed hippocampal activity during both traditional and associative recognition memory tasks. Critically, the hippocampal region was no more active in the associative recognition task than in the traditional recognition task.     

Capacity and limits of associative memory in pigeons

How much information can a brain store over a lifetime’s experience? The answer to this important, but little researched, question was investigated by looking at the long-term visual memory capacity of 2 pigeons. Over 700 sessions, the pigeons were tested with an increasingly larger pool of pictorial stimuli in a two-alternative discrimination task (incremented in sets of 20 or 30 pictures). Each picture was randomly assigned to either a right or a left choice response, forcing the pigeons to memorize each picture and its associated response. At the end of testing, 1 pigeon was performing at 73% accuracy with a memory set of over 1,800 pictures, and the 2nd was at 76% accuracy with a memory set of over 1,600 pictures. Adjusted for guessing, models of the birds’ performance suggested that the birds had access, on average, to approximately 830 memorized picture—response associations and that these were retained for months at a time. Reaction time analyses suggested that access to these memories was parallel in nature. Over the last 6 months of testing, this capacity estimate was stable for both birds, despite their learning increasingly more items, suggesting some limit on the number of picture—response associations that could be discriminated and retained in the long-term memory portion of this task. This represents the first empirically established limit on long-term memory use for any vertebrate species. The existence of this large exemplar-specific memory capacity has important implications for the evolution of stimulus control and for current theories of avian and human cognition.     

On the nature of associative information in recognition memory

In a typical associative-recognition task, participants must distinguish between intact word pairs (both words previously studied together) and rearranged word pairs (both words previously studied but as part of different pairs). The familiarity of the individual items on this task is uninformative because all of the items were seen before, so the only way to solve the task is to rely on associative information. Prior research suggests that associative information is recall-like in nature and may therefore be an all-or-none variable. The present research reports several experiments in which some pairs were strengthened during list presentation. The resulting hit rates and false alarm rates, and an analysis of the corresponding receiver operating characteristic plots, suggest that participants rely heavily on item information when making an associative-recognition decision (to no avail) and that associative information may be best thought of as a some-or-none variable.     

增龄性联结记忆损伤及其影响因素

老年人的联结记忆随年龄增长而出现普遍损伤, 这种增龄性联结记忆损伤究竟是因捆绑功能受损导致的特定损伤还是因整体认知机能受损导致的信息表征能力的整体损伤, 还存有争论。以Naveh-Benjamin (2000)的联结损伤假说(ADH)为代表的特定损伤观认为, 增龄性联结记忆损伤与老年人捆绑不同项目和提取这些捆绑的特定加工过程的损伤有关; 而以Benjamin (2010)的DRYAD模型为代表的整体损伤观则认为, 增龄性联结记忆损伤与老年人因老化而导致的记忆保持精度的整体损伤有关。二者在基本观点、实验支持及存在问题上各有侧重。此外, 影响增龄性联结损伤的因素还可大致分为刺激信息特性、被试主体特点两方面。同时强调未来研究不仅要关注老年人联结损伤的认知机制和影响因素, 更应关注其实际应用和临床指导价值。     

Associative isolation: Unifying associative and list memory

Rather than treating paired associate and serial learning as involving the acquisition of distinct types of information [e.g. Murdock (1974). Human memory: Theory and data. New York: Wiley] I propose an Isolation Principle which treats the two as ends of a continuum. According to this principle, consecutive pairs of items are relatively isolated from other studied items in paired associates learning, but not isolated in serial list learning. The consequence is that variability that dominates forward and backward probed recall is highly correlated in pairs but less so, due to differential interference, in lists. This can explain an important dissociation: whereas forward and backward probes of pairs are nearly perfectly correlated, the correlation is only moderate for serial lists. I demonstrate this in a chaining model by varying item-to-item associative strengths and in a positional coding model by varying the similarity structure of item positions. This enables a range of models to account for data on pairs and lists, as well as potential intermediate or hybrid paradigms, within a single theoretical framework.     

Cuing effects and associative information in recognition memory

Item recognition requires discrimination of studied words from nonstudied words. Associative recognition requires subjects to discriminate studied word groups from recombinations of words from different groups. Cued recognition requires the same old-new discrimination as item recognition, but list items are presented as cues along with the test item. The results from three experiments show (1) little or no effect of cuing for low-frequency words, but (2) positive cuing effects for high-frequency words; (3) increasing levels of overall performance with increases in study time, but (4) unchanging effects of cuing with study time; and (5) stronger positive cuing effects for two cues than for one cue. Five models (Independent Cue Model, Matrix model, MINERVA 2, SAM, and TODAM) were fit to the data of Experiment 1. Each model has trouble with at least one aspect of the results. Theoretical implications and modifications are discussed at length.     

Separating bias and sensitivity in judgments of associative memory

Ratings of the degree of association between words are linearly related to normed associative strengths, but the intercept is high, and the slope is shallow (the judgments of associative memory [JAM] function). Two experiments included manipulations intended to decrease the intercept and increase the slope. Discrimination training on many pairs of words and constraining ratings to sum to a constant both reduced the intercept but failed to change the slope. The intercept of the JAM function appears to contain a bias component that can be manipulated independently of the slope, which reflects sensitivity to associative strengths.     

Effects of aging and IQ on item and associative memory

The effects of aging and IQ on performance were examined in 4 memory tasks: item recognition, associative recognition, cued recall, and free recall. For item and associative recognition, accuracy and the response time (RT) distributions for correct and error responses were explained by Ratcliff's (1978) diffusion model at the level of individual participants. The values of the components of processing identified by the model for the recognition tasks, as well as accuracy for cued and free recall, were compared across levels of IQ (ranging from 85 to 140) and age (college age, 60-74 years old, and 75-90 years old). IQ had large effects on drift rate in recognition and recall performance, except for the oldest participants with some measures near floor. Drift rates in the recognition tasks, accuracy in recall, and IQ all correlated strongly. However, there was a small decline in drift rates for item recognition and a large decline for associative recognition and cued recall accuracy (70%). In contrast, there were large effects of age on boundary separation and nondecision time (which correlated across tasks) but small effects of IQ. The implications of these results for single- and dual-process models of item recognition are discussed, and it is concluded that models that deal with both RTs and accuracy are subject to many more constraints than are models that deal with only one of these measures. Overall, the results of the study show a complicated but interpretable pattern of interactions that present important targets for modeling.