Early declarative memory for location

The abilities of 7.5-month-old infants to recall the location of hidden objects after delays averaging 90 seconds were investigated in three experiments. Various kinds of events were introduced during the delays in order to examine the stability of early location memory. Recall, as shown by reaching towards the correct location, was most clearly found when the infants were allowed either to remain seated facing the hiding locations (Expt 1) or were turned around and immediately re-seated (Expt 2) during the delays. In both experiments, the infants’ attention was diverted from the hiding places, but during all or most of the delay the infants were facing the locations. Recall was dampened when infants were removed from the immediate location of the hiding and engaged in other activities such as looking at a picture during the delay (Expt 3). Further analyses indicated an effect for age that coincides with other research on location memory: evidence for recall was more clearly found for the older, but not the younger, 7-month-olds.     

Forming a stable memory representation in the first year of life: why imitation is more than child's play

Although 9-month-old infants are capable of retaining temporally ordered information over long delays, this ability is relatively fragile. It may be possible to facilitate long-term retention by allowing infants to imitate event sequences immediately after their presentation. The effects of imitation on immediate and delayed recognition and on long-term recall were investigated using event-related potentials (ERPs) and elicited imitation, respectively. Mnemonic facilitation resulting from the opportunity to imitate was apparent using both assessments. ERP assessments at immediate and delayed recognition tests suggested that infants who were allowed to imitate had stronger memory representations of familiar stimuli relative to infants who only viewed the presentation of the events. In addition, infants who were allowed to imitate evidenced higher levels of ordered recall after 1 month relative to infants who only watched the experimenter's demonstration. Therefore, imitation proved to have beneficial effects on explicit memory in 9(1/2)-month-olds, providing evidence of its effectiveness as a tool to augment mnemonic capabilities in infancy.     

The dawning of a past: the emergence of long-term explicit memory in infancy.

The ability to recall information about the past is thought to emerge in the 2nd half of the 1st year of life. Although there is evidence from both cognitive neuroscience and behavioral psychology to support this hypothesis, there is little longitudinal evidence with which the question can be addressed. Infants' memory abilities were tested between the ages of 9 and 16 months using elicited and deferred imitation. Infants' memory for events was tested after delays ranging from 1 to 6 months. The results suggest that at 9 months of age, infants are able to store and retrieve representations over delays of as many as 4 weeks but not over long delays. In contrast, 10-month-olds have at their disposal a system that allows encoding and retrieval of event representations over delays of up to 6 months. These results support the idea that the system that underlies long-term ordered recall emerges near the end of the 1st year of life.     

A Place for Every Event and Every Event in Its Place: Memory for Locations and Activities by 4-Year-Old Children

Episodic memories are of specific events and experiences associated with particular times and places. Whereas memory for the temporal aspects of past events has been a focus of research attention, memory for the location in which events were experienced has been less fully investigated. The limited developmental research suggests that preschool-age children, in particular, may have difficulty remembering the location in which they experienced specific events. In 2 experiments, 4-year-old children engaged in 4 unique activities in 4 unique locations in and around a laboratory suite. In Experiment 1, the children had high levels of recall of the activities, the locations, and the conjunctions of activities and locations, implying that they had formed memory representations that featured activities bound in locations. In Experiment 2, we tested whether 1 element of the bound representation—the location of an activity—served as a reliable cue to recall of the other element—the activity itself. The test was positive, providing further evidence that 4-year-old children form mnemonic conjunctions of activities and locations. The results imply that important elements of episodic memory are available to young children.     

Developmental changes in infants’ visual short-term memory for location

To examine the development of visual short-term memory (VSTM) for location, we presented 6- to 12-month-old infants (N = 199) with two side-by-side stimulus streams. In each stream, arrays of colored circles continually appeared, disappeared, and reappeared. In the changing stream, the location of one or more items changed in each cycle; in the non-changing streams the locations did not change. Eight- and 12.5-month-old infants showed evidence of memory for multiple locations, whereas 6.5-month-old infants showed evidence of memory only for a single location, and only when that location was easily identified by salient landmarks. In the absence of such landmarks, 6.5-month-old infants showed evidence of memory for the overall configuration or shape. This developmental trajectory for spatial VSTM is similar to that previously observed for color VSTM. These results additionally show that infants’ ability to detect changes in location is dependent on their developing sensitivity to spatial reference frames.     

Effects of viewing ordered pictorial reminders on long-term memory in the first year of life

Previous research has shown that reminders can be effective for extending and enhancing a variety of kinds of memory in infants. We investigated the effects of viewing pictorial representations of actions that were included in imitation events used to measure long-term memory in young infants. Infants who saw the pictures of actions displayed in the order in which they comprised events showed evidence of memory for the events. Infants who saw the actions presented randomly did not. These results suggest that pictures presented during the consolidation and storage phase of memory formation can be effective reminders of events for young infants.     

Effects of viewing ordered pictorial reminders on long-term memory in the first year of life

Previous research has shown that reminders can be effective for extending and enhancing a variety of kinds of memory in infants. We investigated the effects of viewing pictorial representations of actions that were included in imitation events used to measure long-term memory in young infants. Infants who saw the pictures of actions displayed in the order in which they comprised events showed evidence of memory for the events. Infants who saw the actions presented randomly did not. These results suggest that pictures presented during the consolidation and storage phase of memory formation can be effective reminders of events for young infants.     

Infant memory for musical experiences

Recent findings suggest that infants can remember words from stories over 2 week delays (Jusczyk, P. W., & Hohne, E. A. (1997). Infants' memory for spoken words. Science, 277, 1984-1986). Because music, like language, presents infants with a massively complex auditory learning task, it is possible that infant memory for musical stimuli is equally powerful. Seven-month-old infants heard two Mozart sonata movements daily for 2 weeks. Following a 2 week retention interval, the infants were tested on passages of the familiarized music, and passages taken from similar but novel music. Results from two experiments suggest that the infants retained the familiarized music in long-term memory, and that their listening preferences were affected by the extent to which familiar passages were removed from the musical contexts within which they were originally learned.     

Emotion, memory, and attention in the taboo Stroop paradigm

This study tested the binding hypothesis: that emotional reactions trigger binding mechanisms that link an emotional event to salient contextual features such as event location, a frequently recalled aspect of naturally occurring flash-bulb memories. Our emotional events were taboo words in a Stroop color-naming task, and event location was manipulated by presenting the words in different task-irrelevant screen locations. Seventy-two participants named the font color of taboo and neutral words, with instructions to ignore word meaning; in one condition, several words were location consistent (i.e., always occupied the same screen location), whereas in another condition, several colors were location consistent. Then, in a surprise recognition memory test, participants recalled the locations of location-consistent words or colors. Although attention enhanced overall location memory for colors (the attended dimension during color naming), emotion (taboo vs. neutral words) enhanced location memory for words but not colors. These results support the binding hypothesis but contradict the hypothesis that emotional events induce image-like memories more often than non-emotional events.     

Keeping the end in mind: Preliminary brain and behavioral evidence for broad attention to endpoints in pre-linguistic infants

Infants must learn to carve events at their joints to best understand who is doing what to whom or whether an object or agent has reached its intended goal. Recent behavioral research demonstrates that infants do not see the world as a movie devoid of meaning, but rather as a series of sub-events that include agents moving in different manners along paths from sources to goals. This research uses behavioral and electrophysiological methods to investigate infants’ (10–14 months) attention to disruptions within relatively unfamiliar human action that does not rely on goal-objects to signal attainment (i.e., Olympic figure skating). Infants’ visual (Study 1, N = 48) and neurophysiological (Study 2, N = 21) responses to pauses at starting points, endpoints, and within-action locations were recorded. Both measures revealed differential responses to pauses at endpoints relative to pauses elsewhere in the action (i.e., starting point; within-action). Eye-tracking data indicated that infants’ visual attention was greater for events containing pauses at endpoints relative to events with pauses at starting points or within-actions. ERP activity reflecting perceptual processes in early-latency windows (<200 ms) and memory updating processes in long-latency windows (700−1000 ms) showed differential activation to disruptions at the end of a figure-skating action compared to other locations. Mid-latency windows (250−750 ms), in contrast, showed enhanced activation at frontal regions across conditions, suggesting electrophysiological resources may have been recruited to encode disruptions within unfamiliar dynamic human action. Combined, results hint at broad sensitivity to endpoints as a mechanism that supports infants’ proclivity for carving continuous and complex event streams into meaningful units. Findings have potential implications for language development as these units are mapped onto budding linguistic representations. We discuss empirical and methodological contributions for action perception and address potential merits and pitfalls of applying behavioral techniques in conjunction with brain-based measures to study infant development.     

Scripts and checkerboards: The influence of ordered visual information on remembering locations in infancy

Five-month-old infants were trained to fixate 4 event locations, and memory for sequential locations was assessed following training. Results of two studies reveal that ordered visual information influences young infants' memory for sequential events.     

Emotional memories are not all created equal: evidence for selective memory enhancement

Human brain imaging studies have shown that greater amygdala activation to emotional relative to neutral events leads to enhanced episodic memory. Other studies have shown that fearful faces also elicit greater amygdala activation relative to neutral faces. To the extent that amygdala recruitment is sufficient to enhance recollection, these separate lines of evidence predict that recognition memory should be greater for fearful relative to neutral faces. Experiment 1 demonstrated enhanced memory for emotionally negative relative to neutral scenes; however, fearful faces were not subject to enhanced recognition across a variety of delays (15 min to 2 wk). Experiment 2 demonstrated that enhanced delayed recognition for emotional scenes was associated with increased sympathetic autonomic arousal, indexed by the galvanic skin response, relative to fearful faces. These results suggest that while amygdala activation may be necessary, it alone is insufficient to enhance episodic memory formation. It is proposed that a sufficient level of systemic arousal is required to alter memory consolidation resulting in enhanced recollection of emotional events.     

Different mental representations for place recognition and goal localization

Determining one’s current location and locating a goal relative to one’s position are important components of successful human navigation in familiar environments. Several prominent cognitive theories of human spatial memory (e.g., McNamara, 2003; Sholl, 2001; Wang & Spelke, 2002) assume that both behaviors access the same enduring mental representations of the environment. Participants in the present experiment learned the locations of seven objects within a room from two views, and were then tested in a separate room using scene recognition and judgments of relative direction (JRD). Scene recognition results indicated that two viewer-centered representations of the layout of objects were preserved in long-term memory, whereas JRD showed evidence of a single orientation-dependent long-term mental representation. The challenges of incorporating the present findings into existing theories of human spatial memory are discussed.     

Biases in long-term location memory in the real world

The category adjustment (CA) approach to distortions in location memory has been largely documented in simplified lab-created spaces but minimally in navigable real-world environments. In the current paper, we extend the approach to a navigable real-world environment and specifically evaluate the assumption that long-term location memory may be retrievable despite errors in recall. Memory for the location of a fountain in a heavily navigated square on a university campus was tested by reproduction on a photograph of the square and then by a forced-choice recognition test. While the recall data showed the standard bias, the recognition data revealed chance-level performance. The pattern of results suggests a possible difference between accessibility of working memories for locations within laboratory-created spaces and long-term memories for locations within complex navigable spaces. The results are discussed in terms of the CA model.     

Doubts about double dissociations between short- and long-term memory

Historically, psychologists and neuroscientists have distinguished between processes supporting memory for events across retention delays of several seconds (short-term memory, STM), and those supporting memory for events across longer retention delays of minutes or more (long-term memory, LTM). Dissociations reported in some neuropsychological studies have contributed to a popular view that there must be neurally distinct memory stores that differentially support STM and LTM. In this article, we review evidence from recent studies regarding dissociations between STM and LTM. We suggest that the evidence reveals problems with claims of selective STM or LTM impairments, which in turn questions whether theories of memory need to propose neurally distinct stores for short- and long-term retention. We consider alternative ways to explain the neural mechanisms of memory across different retention intervals.     

When the event is more than the sum of its parts: 9-month-olds' long-term ordered recall

Research suggests that 9-month-old infants are able to recall single object-specific actions over delays of 24 hours. In the present research we investigated whether 9-month-olds are able to recall over more extended delays, and to recall the temporal order of events, as well as the individual actions in them. In addition, we investigated whether recall can be enhanced by pre- and/or re-exposure to target events. Using elicited imitation of novel, multi-step event sequences, we demonstrated that, as a group, 9-month-olds are able to recall target actions after delays of five weeks. However, after this long delay, only 45% of the infants recalled the temporal order of the events. Re-exposure to events during the delay interval proved necessary for boys, but not for girls; pre-exposure to events did not affect later recall. The implications of individual differences in infants' recall ability for the understanding of the development of the neural correlates of declarative memory are discussed.     

Tests of the duomemory notion for movement information

The validity of the duomemory notion (i.e. the concept of two separate memory systems, one for recently presented events and another for learned acts) for motor behavior was tested in an experiment which sought to determine the extent to which interference differentially influenced the recall of a movement when it is initially experienced and after it is repeatedly practiced. Using a traditional linear-positioning task, subjects moved to five defined target locations on each trial and after a retention interval attempted to recall the targets in reverse order. One location was repeated on each of 10 trials while the others were always different. Control subjects were presented and recalled only the repeated criterion location on each trial. The results indicated (a) a constant superiority of criterion recall accuracy for the control condition throughout the 10 trials and (b) and absence of improvement over practice by the experimental group in the recall of the criterion location relative to that of nonrepeated targets. The findings were interpreted as a lack of support for the duomemory notion, and the exploration of an alternative framework (Craik & Lockhart, 1972) for the investigation of memory for movement information was suggested.     

Infants' delayed recognition memory for colour and form

Delayed recognition memory was investigated in 5- and 9-week-old infants after extensive familiarization to a visual stimulus. Both age groups were found to demonstrate memory for colour and form information after a 24 hour delay. In addition the location of testing, relative to the location of familiarization, was found to influence the apparent strength of memory, while there was no effect of sex nor evidence of additivity of stimulus dimensions.     

Developmental continuity in the processes that underlie spatial recall

This study investigated whether children's spatial recall performance shows three separable characteristics: (1) biases away from symmetry axes (geometric effects); (2) systematic drift over delays; and (3) biases toward the exemplar distribution experienced in the task (experience-dependent effects). In Experiment 1, the location of one target within each geometric category was varied. Children's responses showed biases away from a midline axis that increased over delays. In Experiment 2, multiple targets were placed within each category at the same locations used in Experiment 1. After removing geometric effects, 6-year-olds'--but not 11-year-olds'--responses were biased toward the average remembered location over learning. In Experiment 3, children responded to one target more frequently than the others. Both 6- and 11-year-olds showed biases toward the most frequent target over learning. These results provide a bridge between the performance of younger children and adults, demonstrating continuity in the processes that underlie spatial memory abilities across development.