Synesthesia and memory: color congruency, von Restorff, and false memory effects

In the current study, we explored the influence of synesthesia on memory for word lists. We tested 10 grapheme-color synesthetes who reported an experience of color when reading letters or words. We replicated a previous finding that memory is compromised when synesthetic color is incongruent with perceptual color. Beyond this, we found that, although their memory for word lists was superior overall, synesthetes did not exhibit typical color- or semantic-defined von Restorff isolation effects (von Restorff, 1933) compared with control participants. Moreover, our synesthetes exhibited a reduced Deese-Roediger-McDermott false memory effect (Deese, 1959; Roediger & McDermott, 1995). Taken as a whole, these findings are consistent with the idea that color-grapheme synesthesia can lead people to place a greater emphasis on item-specific processing and surface form characteristics of words in a list (e.g., the letters that make them up) relative to relational processing and more meaning-based processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved).     

Age-related differences in the von Restorff isolation effect

When one item is made distinct from the other items in a list, memory for the distinctive item is improved, a finding known as the isolation or von Restorff effect (after von Restorff, 1933). Although demonstrated numerous times with younger adults and children, this effect has not been found with older adults (Cimbalo & Brink, 1982). In contrast to the earlier study, we obtained a significant von Restorff effect for both younger and older adults using a physical manipulation of font colour. The effect size for older adults was smaller than that obtained for younger adults, confirming a prediction of Naveh-Benjamin's (2000) associative deficit hypothesis, which attributes age-related differences in memory performance to older adults' reduced ability to form associations. The findings are consistent with related research in which older adults demonstrate similar—but smaller—benefits for distinctive information to those for younger adults.     

The generation effect: dissociating enhanced item memory and disrupted order memory

Generating stimuli at encoding typically improves memory for occurrence (item memory) but might disrupt memory for order. In three experiments, the relationship between generation and order memory was examined by using familiar stimuli, which give rise to the standard generation advantage in item memory, and unfamiliar stimuli, which do not. The participants generated or read words and non-words in Experiments 1 and 2 and familiar and unfamiliar word compounds in Experiment 3. For the familiar stimuli, generation enhanced item memory (as measured by recognition) but disrupted performance on the order-reconstruction test. For the unfamiliar stimuli, generation produced no recognition advantage and yet persisted in disrupting order reconstruction. Thus, the positive effects of generation on item memory were dissociated from its negative impact on order memory.     

Time,space, and memory for order

Information about the order of items in a sequence can be conveyed either spatially or temporally. In the present investigation, we examined whether these different modes of presentation map onto compatible mental representations of serial order. We examined this issue in three immediate serial-recall experiments, in which participants recalled lists of letters in the temporal order in which they had appeared. Each letter in a to-be-remembered sequence was presented in a unique spatial position, with the order of these spatial positions progressing from either left to right or right to left. In this way, the visually presented lists contained both temporal and spatial order information. Recall of the temporal order information was more accurate with congruent spatial order information—that is, when the letters progressed from left to right, following the typical reading direction of English—than when the spatial order information was incongruent. These results suggest compatible representations of serial order when sequences are conveyed spatially and temporally.     

Integrated memory for objects, places, and temporal order: evidence for episodic-like memory in mice

Human episodic memory refers to the recollection of an unique past experience in terms of what happened, and where and when it happened. Factoring out the issue of conscious recollection, episodic memory, even at the behavioral level, has been difficult to demonstrate in non-human mammals. Although, it was previously shown that rodents can associate what and when or what and where information given on unique trials, it proved to be difficult to demonstrate memory for what, where, and when simultaneously in mammals, without using extensive training procedures, which might induce semantic rather than episodic memory recall. Towards the goal of an animal model of human episodic memory we designed an three-trial object exploration task in which different versions of the novelty-preference paradigm were combined to subsume (a) object recognition memory, (b) the memory for locations in which objects were explored, and (c) the temporal order memory for object presented at distinct time points. We found that mice spent more time exploring two "old familiar" objects relative to two "recent familiar" objects, reflecting memory for what and when and concomitantly directed more exploration at a spatially displaced "old familiar" object relative to a stationary "old familiar" object, reflecting memory for what and where. These results suggest that during a single test trial the mice were able to (a) recognize previously explored objects, (b) remember the location in which particular objects were previously encountered, and (c) to discriminate the relative recency in which different objects were presented. According to the currently discussed behavioral criteria for episodic-like memory in animals, our results suggest that mice are capable to form such higher order memories.     

Attention, rehearsal, and memory for serial order

In three experiments, subjects attended to one of two simultaneous nine-digit sequences, presented binaurally in different voices (one male, one female). Substantial repetition effects (defined as gains in immediate memory performance for previously presented sequences relative to novel ones) were found for two exposure conditions: (a) one that required reproduction of the full sequence on each exposure (Experiment 1), and (b) one that required recall of a different two-digit subsequence on each exposure (Experiment 2). In Experiment 3, the following conditions produced no repetition effects, even though tests had substantial power to detect small effects: 10 consecutive presentations in the unattended voice; 4 prior presentations in a task that required attention to each digit as it was presented (but not to digit order); and 4 prior presentations in a task that required attention to digit order during their presentations. These results, together with those of previous studies, support the conclusion that repetition effects on immediate memory occur only with procedures that encourage covert rehearsal of full-sequence order on each exposure. These findings also limit the generality of others' conclusions that event order is automatically encoded for attended events, and extend previous findings showing unattended exposures to be without effect on recall measures.     

Short-term recall of order information: Influence of encoding and generation processes on distinctiveness,isolation, and background effects

We examined the influence of encoding and generation processes on distinctiveness, isolation, and background effects in short-term recall of order information. Adults recalled the order of letters in one of two segments following a distractor task, knowing in advance the identity of the letters. A distinctive letter was one that was either in red or absent and replaced with a red dash, thereby requiring generation. On trials with a distinctive letter, the letter was primed in advance. A negative generation effect was found; in addition, there was a positive distinctiveness effect but a negative background effect on trials in which generation was required. These effects can be explained in terms of the extra processing given to distinctive items when they need to be generated.     

Traveling economically through memory space: Characterizing output order in memory for serial order

How do people report the contents of short-term memory when information about order must be retained but items can be retrieved in any order? We report an experiment using an unconstrained reconstruction task in which people can report list items in any order but must place them in their correct serial positions. We found (1) a tendency to report recent items first in immediate but not in delayed reconstruction, (2) a tendency to recall temporally isolated items first, (3) a preference for forward recall order, and (4) a preference for output orders that minimize the length of the path that must be traversed through memory space during retrieval. The results constrain most current models of short-term memory in which retrieval is ballistic and is assumed to run to completion autonomously once initiated.     

The von Restorff effect and induced amnesia: production by manipulation of sound intensity.

When an outstanding item appears in an otherwise homogeneous list of items, the outstanding item is better remembered (the von Restorff effect), and items before and after it may be more poorly remembered (induced amnesia) than corresponding items in a control list. In the present experiments the outstanding item was a word presented as a loud shout among other words presented at normal conversational levels. In two experiments, large retrograde- and anterograde-induced amnesiae effects were demonstrated using a free-recall and a recognition task. In both experiments half of the subjects were told what to expect and were instructed to devise a strategy to eliminate induced amnesia. These instructions failed to eliminate the amnesiac effect. A third experiment was designed to demonstrate an empirical similarity between induced and clinical amnesia. In clinical retrograde (but not anterograde) amnesia, "lost" memories are sometimes recovered with time. Filled delays of 0, 30, or 120 sec interpolated between list presentation and recall demonstrated that induced retrograde amnesia disappeared at the longest delay but induced anterograde amnesia was unchanged. A fourth experiment eliminated some alternate interpretations of the effect.     

Word frequency and memory: effects on absolute versus relative order memory and on item memory versus order memory

Word frequency can produce opposite effects on recognition and order memory: Low-frequency words produce greater recognition accuracy, whereas high-frequency words produce superior order memory. The present experiments further delineate the relationship between word frequency and order memory. Experiment 1 indicates that low-frequency words produce worse performance on a measure of absolute order memory but not on a test of relative order, which is consistent with the idea that different forms of information underlie different types of order judgments (Greene, Thapar, & Westerman, 1998). Experiment 2 contrasted high-, low-, and very low-frequency words on recognition memory and absolute order memory. In comparison with high-frequency words, low-frequency words enhanced recognition, whereas very low-frequency words did not. Both low- and very low-frequency words, however, produced worse memory for absolute order. Thus, the relationship between frequency and item memory is an inverted U-shaped function, whereas the relationship between frequency and absolute order memory is direct. This implies that the item-enhancing effects of lower word frequency may be dissociated from its order-disrupting effects.     

The von Restorff effect and measures of organization in normals and retardates

Thirty-two noninstitutionalized retardates and 32 normals of equal mental age (approximately 8 years) heard 10 orders of 10 nouns when the decibel (dB) level of the stimuli was the same and when the dB level of the sixth item was higher. The yon Restorff effect was demonstrated by both groups. The normals’ overall recall was superior to that of the retardates’ recall. Differences in recall were attributed to the normals’ tendency to recall items in the same serial order more consistently. The subjective organization of lists, as measured by order of recall, differed for the normals and retardates; the normal group was more adaptable than the retarded group in adjusting their strategy to different list conditions.     

Hemispheric memory for random forms revisited

Hemispheric short-term memory was studied by projecting complex random forms that varied in their verbal association strength to the left and right hemispheres. Male and female subjects responded same or different to a centrally presented memory test stimulus which occurred 0, 5, 10, or 20 sec after the target item. Reaction time for both response judgments was significantly shorter for right-hemisphere presentations over all memory intervals. For both performance measures, response judgment interacted with the length of memory interval and the verbal association value of the stimulus items. No hemispheric differences were observed as a function of subject sex. Hemispheric memory for complex forms appears primarily dependent upon task processing demands rather than stimulus factors when response time is used to measure recognition under tightly controlled conditions.     

Sex differences in memory estimates,revisited

207 undergraduate students (95 men and 112 women) representing all four years in college provided estimates of memory performance before and after a recall task involving 80 stimuli (41) pictures and 40 words). The study was intended as a replication of the work of Ionescu in 2000 wherein men underestimated their performance on the picture items and women underestimated their performance on the words. No sex differences were found for correct recall totals, recall for pictures, recall for words, and total prerecall performance estimates. Although both men and women underestimated their pre- and postrecall performance, women underestimated their postrecall performance more than men. More importantly, men underestimated their performance on recall of pictures, whereas women underestimated their performance on the word items, thereby validating prior results with a larger sample. The possible bases for this phenomenon are still not clear.     

Oscillator-based memory for serial order

A computational model of human memory for serial order is described (OSCillator-based Associative Recall [OSCAR]). In the model, successive list items become associated to successive states of a dynamic learning-context signal. Retrieval involves reinstatement of the learning context, successive states of which cue successive recalls. The model provides an integrated account of both item memory and order memory and allows the hierarchical representation of temporal order information. The model accounts for a wide range of serial order memory data, including differential item and order memory, transposition gradients, item similarity effects, the effects of item lag and separation in judgments of relative and absolute recency, probed serial recall data, distinctiveness effects, grouping effects at various temporal resolutions, longer term memory for serial order, list length effects, and the effects of vocabulary size on serial recall.     

Remembering the forgotten? Reminiscence, hypermnesia and memory for order

Three experiments established that repeated testing affects item and order retention differently: Hypermnesia was found with repeated free recall tests, whereas net performance declined significantly across successive free reconstruction of order tests. Overall order performance declined over tests under a variety of encoding conditions (pictures, words, and relational and item-specific processing) and retrieval conditions (intentional and incidental learning). Although net performance dropped across tests, participants did show reliable order recovery (reminiscence) between tests. The implications of these data for general theories of hypermnesia and order are discussed.