A motor isolation effect: When object manipulability modulates recall performance

Previous studies suggested that the language production architecture is recruited during verbal retention, and others proposed that spatial memory relies on the oculomotor system. The objective of the present study was to investigate the role of the motor system in object memory, by examining the effect of objects' affordances on retention. In a serial recall task, we manipulated the manipulability of objects to retain in memory. We used an isolation paradigm where we isolated the manipulability level of one object from the list. We showed that recall performance improved for the isolated object (Experiment 1) and that this advantage was abolished when participants were required to perform motor suppression during the task (Experiment 2). In Experiment 3, we showed that the abolition of the motor isolation effect in Experiment 2 was not due to an effect of distraction since motor suppression was shown not to interfere with a semantic isolation effect. It is argued that motor affordances play a role in object memory, but only when the motor characteristics of an object allow discriminating it from the other objects in the list.     

Scene‐context effect in visual memory is independent of retention interval1

The context of a natural scene can facilitate memory for embedded objects. It has been reported that such scene‐context effects can be lost in the flicker paradigm, which alternatively presents a picture, followed by a modified version of the picture after a brief interval. Using a follow‐the‐dot paradigm which instills serial attending, determinants of the scene‐context effect are examined by varying both scene‐context (normal, jumbled) and the retention interval (short, long) between cued and target objects. In this paradigm, a dot cue was sequentially presented on 12 different objects of a scene, then the memory for one of the cued objects was tested. This paradigm requires holding information about multiple objects in memory at once. Retention intervals were varied by manipulating the serial position of the dot on a target object. The results showed that the retention interval did not influence the scene‐context effect. Potential mechanisms for the scene‐context effect are discussed.     

Support for a theory of memory for event duration must distinguish between test-trial ambiguity and actual memory loss

Staddon and Higa's (1999) trace-strength theory of timing and memory for event duration can account for pigeons' bias to "choose short" when retention intervals are introduced and to "choose long" when, following training with a fixed retention interval, retention intervals are shortened. However, it does not account for the failure of pigeons to choose short when the intertrial interval is distinct from the retention interval. That finding suggests that stimulus generalization (or ambiguity) between the intertrial interval and the retention interval may result in an effect that has been attributed to memory loss. Such artifacts must be eliminated before a theory of memory for event duration can be adequately tested.     

Spatial memory in rats after 25 hours

We investigated the time course of spatial-memory decay in rats using an eight-arm radial maze. It is well established that performance remains high with retention intervals as long as 4 h, but declines to chance with a 24-h retention interval (Beatty, W. W., & Shavalia, D. A. (1980b). Spatial memory in rats: time course of working memory and effect of anesthetics. Behavioral & Neural Biology, 28, 454-462). It is possible that 24 h reflects a genuine retention limitation of rat spatial memory. Alternatively, it may be possible to identify factors that might support memory performance even after very long delays. The current experiment was conducted to test the above two hypotheses. We evaluated performance using two intertrial intervals (24 and 48 h) and two retention intervals (1 and 25 h). Increasing the intertrial interval produced an approximately constant increase in performance for both retention intervals. This improvement is consistent with a trial-spacing effect (i.e., the superiority of spaced over massed trials). Rat spatial memory apparently lasts at least 25 h.     

Short-term memory for temporal intervals: Contrasting explanations of the choose-short effect in pigeons

To better understand short-term memory for temporal intervals, we re-examined the choose-short effect. In Experiment 1, to contrast the predictions of two models of this effect, the subjective shortening and the coding models, pigeons were exposed to a delayed matching-to-sample task with three sample durations (2, 6 and 18 s) and retention intervals ranging from 0 to 20 s. Consistent with the coding model, the results suggested a sudden forgetting of memories for duration. In Experiment 2, to test the confusion hypothesis, the characteristics of the ITI and the retention interval differed. Contrary to the confusion hypothesis, a choose-short effect was obtained. In both experiments, a test with only two of the three comparison keys was performed. The results suggest three effects that may be controlling the birds’ responses: stimulus generalization when no retention interval is present; an increase in random responding at longer retention intervals; and, similarly, an increase in preference for the “short-sample” key at longer retention intervals.     

Mnemonic benefits of retrieval practice at short retention intervals

The testing effect refers to the retention benefit conferred by prior retrieval of information from memory. Although the testing effect is a robust phenomenon, a common assumption is that reliable memory benefits only emerge after long retention intervals of days or weeks. The present study focused on potential test-induced retention benefits for brief retention intervals on the order of minutes and tens of seconds. Participants in four experiments studied lists of words. Some of the items were subjected to an initial cued recall test, and others were re-presented for additional study. Free recall tests were administered in each experiment following retention intervals ranging from 30 s to 8 min. When initial retrieval practice was successful (Experiments 1 through 3), or feedback compensated for unsuccessful retrieval (Experiment 4), significant testing effects emerged at all retention intervals. Results are discussed in the context of a bifurcated item-distribution model and highlight the importance of initial test performance and the type of analysis employed when examining testing effect data.     

Recognition memory retention interval and information load

Two experiments were conducted to study the effect of retention interval and information load on short-term recognition memory in retarded subjects. The task consisted of an input trial of 1–15 pictures followed by a test trial of one picture, with the subject having to press different levers to indicate whether the probe picture had been present on the input trial. Retention intervals between input trial and test trial were manipulated over a range of 1–24 sec. Both accuracy and latency of response were measured. Results showed that latency increased and accuracy decreased as a function of both retention interval and number of stimuli. In addition, number of stimuli interacted with retention interval such that accuracy was not affected by retention interval when information input was small, but decreased quite dramatically at longer retention intervals when input was larger. The results were discussed in terms of current memory search models for both normal and retarded subjects.     

Is perceptual salience needed in explanations of the isolation effect?

The isolation effect is a well-known phenomenon that has a well-accepted explanation: An item that is isolated on a list becomes perceptually salient, which leads to extra rehearsal that enhances memory for the isolate. To evaluate this hypothesis, the authors isolated an item near the beginning of a list. Immediately after each item was presented for study, participants judged the likelihood of recalling the item. Although the isolation effect occurred, participants did not judge the isolate as being more memorable than the preceding item, suggesting that the isolate was not salient. In a second experiment, participants rehearsed items aloud. Isolation at the beginning of the list did not produce extra rehearsal. By contrast, isolation in the middle of the list produced extra rehearsal; however, even when the isolate did not receive extra rehearsal, an isolation effect was evident. Thus, salience and extra rehearsal are not necessary for producing an isolation effect.     

Advance preparation in task switching: what work is being done?

The preparation effect in task switching is usually interpreted to mean that a switching process makes use of the interval between task-cue onset and trial-stimulus onset (the cue-stimulus interval, or CSI) to accomplish some of its work ahead of time. This study undermines the empirical basis for this interpretation and suggests that task activation, not task switching, is the functional process in cognitive control. Experiments 1 and 2 used an explicit cuing paradigm, and Experiments 3 and 4 used a variation in which the trial after a task cue was followed by several cueless trials, requiring retention of the cue in memory. Experiments 1 and 3 replicated the preparation effect on switch cost, and Experiments 2 and 4 showed that this effect vanishes when CSI is manipulated between subjects, leaving only a main effect of CSI when the task cue is a memory load.     

Adaptive memory: longevity and learning intentionality of the animacy effect

The animacy effect—the finding that animates are better remembered than inanimates—is proving to be a robust empirical phenomenon. Considering the adaptiveness of the animate advantage, one might expect it to remain after long retention intervals and also to be present irrespectively of an intention to learn. The present study explores these two aspects. Different groups of participants learned (intentional learning) or rated the pleasantness (incidental learning) of animate and inanimate words; memory was tested immediately or after a 48?h delay. A significant animacy effect was obtained after both retention intervals and in both learning conditions. Two significant interactions revealed a larger animacy effect, as well as a larger effect of the retention interval, when learning was incidental. Our findings reinforce the robustness of the animacy effect and provide some insight into possible proximate mechanisms of the effect.     

Long-term memory of color stimuli in the jungle crow (Corvus macrorhynchos)

Wild-caught jungle crows (n = 20) were trained to discriminate between color stimuli in a two-alternative discrimination task. Next, crows were tested for long-term memory after 1-, 2-, 3-, 6-, and 10-month retention intervals. This preliminary study showed that jungle crows learn the task and reach a discrimination criterion (80% or more correct choices in two consecutive sessions of ten trials) in a few trials, and some even in a single session. Most, if not all, crows successfully remembered the constantly reinforced visual stimulus during training after all retention intervals. These results suggest that jungle crows have a high retention capacity for learned information, at least after a 10-month retention interval and make no or very few errors. This study is the first to show long-term memory capacity of color stimuli in corvids following a brief training that memory rather than rehearsal was apparent. Memory of visual color information is vital for exploitation of biological resources in crows. We suspect that jungle crows could remember the learned color discrimination task even after a much longer retention interval.     

Effects on memory of early testing and accuracy assessment for central and contextual content

ABSTRACT

Memory for an event is influenced by many factors including retention interval, frequency of assessment, and type of information assessed concerning the event. We examined the usefulness of observer memory for contextual information in assessing accuracy of memory for central information. Participants viewed a video of a purse being stolen and were asked questions concerning the perpetrator and surrounding context of the event, including where and when the event occurred and who else was present. Participants tested immediately after seeing the video exhibited better memory than those tested for the first time 48 hours after the event. Additionally, testing immediately after viewing the video reduced forgetting over the 48-hour delay (i.e. early testing attenuated subsequent forgetting). Moreover, memory for the context of the event correlated positively with memory of the central information (i.e. perpetrator), and memory concerning other people at the event tended to have the highest correlation with perpetrator memory.     

Intention to respond in a special way offers some protection against forgetting associations

In a continuous memory-updating paradigm, subjects studied name-color associations and were tested later for the color associate given the name. The default color response was made in one location, but on predesignated trials the response was required to be made in a special location. Memory for the color associated with a given name was assessed after short and long retention intervals when both default and special responses were required. Separate measures were examined of memory for the intention to respond in a particular way (default or special) and of memory for the color associations paired with the names. Memory for color associates was better overall with short than with long retention intervals and was better when special (rather than default) responses were required, especially at the long retention interval. These results imply that the requirement to respond in a special way protects associations from loss due to forgetting.     

Practice and forgetting effects on vocabulary memory: an activation-based model of the spacing effect

An experiment was performed to investigate the effects of practice and spacing on retention of Japanese–English vocabulary paired associates. The relative benefit of spacing increased with increased practice and with longer retention intervals. Data were fitted with an activation-based memory model, which proposes that each time an item is practiced it receives an increment of strength but that these increments decay as a power function of time. The rate of decay for each presentation depended on the activation at the time of the presentation. This mechanism limits long-term benefits from further practice at higher levels of activation and produces the spacing effect and its observed interactions with practice and retention interval. The model was compared with another model of the spacing effect (Raaijmakers, 2003) and was fit to some results from the literature on spacing and memory.     

The time course of spatial memory distortions

Four experiments investigated the memory distortions for the location of a dot in relation to two horizontally aligned landmarks. In Experiment 1, participants reproduced from memory a dot location with respect to the two landmarks. Their performance showed a systematic pattern of distortion that was consistent across individual participants. The three subsequent experiments investigated the time course of spatial memory distortions. Using a visual discrimination task, we were able to map the emergence of spatial distortions within the first 800 msec of the retention interval. After retention intervals as brief as 50 msec, a distortion was already present. In all but one experiment, the distortion increased with longer retention intervals. This early onset of spatial memory distortions might reflect the almost immediate decay of detailed spatial information and the early influence of an enduring spatial memory representation, which encodes spatial information in terms of the perceived structure of space.     

Place learning in the Morris water task: making the memory stick

Although the Morris water task has been used in hundreds of studies of place learning, there have been no systematic studies of retention of the place memory. We report that retention, as measured by selective search behavior on a probe trial, is excellent when the retention interval is short (5-10 min). However, performance rapidly deteriorates, so that by approximately 4 h the search is no longer selective. Additional experiments revealed that selective search at longer retention intervals was improved by inserting gaps between blocks of training trials, but this effect was a non-monotonic function of the interval separating trial blocks. Our experiments also revealed that the location of the first block of trials (Room A or Room B) was irrelevant to long-term retention. A memory modulation theoretical framework may provide a useful way to understand these findings.     

Massed and spaced learning in honeybees: the role of CS, US, the intertrial interval, and the test interval

Conditioning the proboscis extension reflex of harnessed honeybees (Apis mellifera) is used to study the effect temporal spacing between successive conditioning trials has on memory. Retention is monitored at two long-term intervals corresponding to early (1 and 2 d after conditioning) and late long-term memory (3 and 4 d). The acquisition level is varied by using different conditioned stimuli (odors, mechanical stimulation, and temperature increase at the antenna), varying strengths of the unconditioned stimulus (sucrose), and various numbers of conditioning trials. How learning trials are spaced is the dominant factor both for acquisition and retention, and although longer intertrial intervals lead to better acquisition and higher retention, the level of acquisition per se does not determine the spacing effect on retention. Rather, spaced conditioning leads to higher memory consolidation both during acquisition and later, between the early and long-term memory phases. These consolidation processes can be selectively inhibited by blocking protein synthesis during acquisition.     

Stimulus and procedural determinants of the forgetting of conditioned fear.

Two studies investigated factors believed to influence the retention of acquired fear in rats. The results show clearly that the lack of forgetting over 24-hr interval reported by previous investigators is due to a depression of performance on the immediate test (3-min retention interval) resulting from the procedure of not handling the rats during conditioning but then handling them on every trial during the retention test. In accord with the McAllister's interpretation of related results, the depression of performance after short retention intervals may be due to a lack of generalization from training to the testing situation. As the retention interval is lengthened, the amount of generalization increases and escape performance improves on a relative basis. The nature of the retention function may be severely distorted by selection of an inappropriate paradigm for its evaluation.     

Differential effectiveness of various prior-cuing treatments in the reactivation and maintenance of memory

In 3 experiments, changes were examined in the characteristics of newly acquired and reinstated memories over time in preweanling rats. Experiment 1 indicated that forgetting after conditioning was monotonic, with the upper limit of retention at approximately 120 min posttraining. In Experiment 2, Ss were exposed to various elements of the training episode before testing, after either a 3- or a 24-hr retention interval. The results indicated that the prior-cuing treatments were differentially effective and that the effectiveness of a reactivation treatment may change as a function of the retention interval. Experiment 3 indicated that Ss expressed a conditioned aversion at much longer intervals following reactivation treatments than after initial conditioning. Furthermore the susceptibility of the reinstated memory to forgetting was dependent on the prior-cuing treatment used. The results suggest a change in the memorial representation of the conditioning episode over time.     

Retention interval modulates the effect of negative arousing pictures on recognition memory

This study examined the modulation of retention interval in the effect of emotion as elicited from negative and positive arousing pictures on recognition memory. Participants underwent seven encoding sessions and one testing session. The encoding sessions were separated by certain lengths of intervals such that there were seven levels of time gaps between encoding and testing. In each encoding session, participants learned a list of 30 pictures (including 10 neutral, 10 positive and 10 negative pictures). In the testing session, they were presented with a list of 210 old and 210 new pictures and made “old/new” and “remember/know” judgements. The results showed that negative arousing pictures enhanced overall recognition in the 2-week interval and enhanced recollection in both the 2-week and 3-week intervals. However, neither negative nor positive arousing pictures had any effect on familiarity regardless of retention interval. The current study contributes to the literature by suggesting that longer retention intervals do not necessarily lead to more pronounced effects of negative arousing pictures and that the modulation of retention interval depends on the specific components of recognition memory.