An empirical note on the role of verbal labels in motor short-term memory tasks

Previous studies of motor short-term memory have shown that when a criterion movement on a semicircular positioning task is accompanied by an appropriate verbal label (a clock-face position), recall of the movement is more accurate than when only the movement is presented. This increased accuracy could be due to either the additional spatial information provided by the label or enhanced retention of the movement information. These two alternatives cannot be distinguished on the basis of previous studies because the studies have not evaluated movement accuracy following presentation of the label alone. The present study employed such a condition in addition to the movement-only and movement-plus-label conditions to distinguish between the two hypotheses. In all conditions, subjects were asked to move to the criterion position after a retention interval of either 5 sec or 60 sec. Evidence indicated that subjects who received both the label and the movement tended to use the spatial information provided by the label at the 60-sec interval. The evidence did not indicate that the verbal label actually enhanced retention of the movement information.     

An Empirical Note on the Role of Verbal Labels in Motor Short-Term Memory Tasks

Previous studies of motor short-term memory have shown that when a criterion movement on a semicircular positioning task is accompanied by an appropriate verbal label (a clock-face position), recall of the movement is more accurate than when only the movement is presented. This increased accuracy could be due to either the additional spatial information provided by the label or enhanced retention of the movement information. These two alternatives cannot be distinguished on the basis of previous studies because the studies have not evaluated movement accuracy following presentation of the label alone. The present study employed such a condition in addition to the movement-only and movement-plus-label conditions to distinguish between the two hypotheses. In all conditions, subjects were asked to move to the criterion position after a retention interval of either 5 sec or 60 sec. Evidence indicated that subjects who received both the label and the movement tended to use the spatial information provided by the label at the 60-sec interval. The evidence did not indicate that the verbal label actually enhanced retention of the movement information.     

Integration of cardiac responses to serial stimuli after Pavlovian conditioning in rats

The expression of cardiac responses to sequences of two sounds was studied in restrained rats following discriminative trace or delay conditioning. Stimuli paired with a tail shock 10 sec later (CS1) elicited conditioned bradycardia. Unpaired or neutral stimuli (CS0) elicited mostly tachycardia. Rats did not learn to suppress responding to nonreinforced sequences with an interval of 6 sec between sounds. Responses to the second stimulus were significantly augmented following a CS1 stimulus, but not following a CS0 stimulus. Real-time summation of simple responses provided a more complete and quantitative prediction of dual responses than did resetting or facilitation. These results extend the time range over which summation may be observed from less than 2 sec to at least 16 sec. They appear to be inconsistent with models involving competition between unitary representations of stimuli in short-term memory and suggest the existence of multiple stimulus traces with independent time courses.     

Memorial psychophysics for visual area: The effect of retention interval

Previous studies (e.g., Kerst & Howard, 1978) have shown that remembered visual areas are related to actual areas by a more compressive power function than are perceived visual areas. Experiment 1 useda between-groups design to replicate this effect for a map of Europe and showed that compression increased as the retention interval, the time between map inspection and area estimation, increased from 2 min to 1 week. Experiment 2 obtained similar results with a similar design, except that a simple two-region map was used to reduce uncertainty. Overall, the results suggest that two processes may be operating: uncertainty and gradual transformation of the representation of the map in memory.     

Need probability affects retention: A direct demonstration

Recent memory theory has emphasized the concept ofneed probability—that is, the probability that a given piece of learned information will be tested at some point in the future. It has been proposed that, in real-world situations, need probability declines over time and that the memory-loss rate is calibrated to match the progressive reduction in need probability (J. R. Anderson & Schooler, 1991). The present experiments were designed to examine the influence of the slope of the need-probability curve on the slope of the retention curve. On each of several trials, subjects memorized a list of digits, then retained the digits in memory for 1, 2, 4, 8, or 16 sec. Some trials ended with a recall test; other trials ended with the message, “no test.” In Experiment 1, the likelihood of encountering a memory test (i.e., the need probability) was made to either increase or decrease as the retention interval increased; in Experiment 2, need probability either was flat (invariant across retention intervals) or decreased as the retention interval increased. The results indicated that the shape of the need-probability curve influenced the slope of the retention curve (Experiment 1) and that the effect became larger as the experimental session progressed (Experiment 2). The findings support the notion that memory adapts to need probabilities and that the rate of forgetting is influenced by the slope of the need-probability curve. In addition, all of the forgetting curves approximated a power function, suggesting that need probability influences the slope but not the form of forgetting.     

时间判断的视听通道效应的实验研究

该实验用视觉或听觉两种方式一次呈现两个时距,随机地指定其中的一个时距要求被试立即再现或延迟5秒再现。实验结果表明:①对短时距信息(1秒,1.5秒,2秒)的判断,听觉比视觉具有明显的优势,听觉的再现时距较精确,延迟对听觉的时间信息检测的破坏作用较小;而对长时距信息(10秒,11秒,12秒)的判断,却未发现听觉比视觉有优势现象。②通道效应的产生机制源于记忆的特点而不是感觉储存的特点。③对短时距的判断通常表现为正时间顺序误差,而对长时距的判断则表现为负时间顺序误差。     

Retention of time information in forced-choice duration discrimination

We explore the effect on performance in a forced-choice duration-discrimination task of varying the interstimulus interval (ISI) from 0 to 2 sec. The durations were brief empty intervals (115–285 msec) bounded by very brief auditory pulses. Performance improved as the ISI increased from 0 to 1/2 sec, but a further increase in ISI up to 2 sec resulted in little further change in performance. The “time information” derived from a brief interval bounded by auditory pulses does not appear to be susceptible to the very short-term perceptual memory loss inferred in other auditory discriminations.     

The fate of ear asymmetries in short-term memory

Recognition memory for word lists presented to left or right ears was tested after filled retention intervals of 0-to 60-sec duration. Experiment 1 showed that the right-ear advantage (REA) for immediate recognition in dichotic listening does not occur after 10 sec delay. In Experiment 2, monaural presentation produced a nonsignificant REA which did not appear to be affected by delay. These data suggest that the REA for immediate report usually observed in the dichotic listening situation is a transient phenomenon which is based on phonetic encoding. The left hemisphere seems to be specialized for the initial reception of verbal information, but not for the storage or retention of such information over time.     

Short-term temporal changes in free recall

An experimental study of short-term memory for lists of familiar English words is reported. Lists of 10, 20, and 30 unrelated words were presented at a 1-sec. rate. Retention was measured by free recall after intervals of 0, 15 and 30 sec. A counting task was used to prevent rehearsal during the retention interval. The absolute level of recall increased with length of list whereas the percentages retained showed the reverse trend. The recall scores decreased steadily as a function of retention interval, with the rates of forgetting comparable for the three lengths of list. The decline in the amount recalled was due in large measure to the loss of the terminal items in the list. Consequently, the pronounced recency effect present on the immediate test of recall was progressively reduced as a function of time. By contrast retention of the initial part of the list was relatively stable. These variations in rate of forgetting are attributed to differences among serial positions in susceptibility to proactive inhibition.     

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.     

The Temporal Placement of Interpolated Movements in Short-Term Motor Memory,

Directional response biasing as a function of the recency of an interpolated act was examined on a lever device in a within-S design. The temporal occurrence of an interpolated act was systematically varied (5, 30, or 55 sec. after the criterion act) for three retention intervals (15, 40, and 65 sec.), and the location of the interpolated movement was held constant ± 40 deg. from the criterion position. Analysis of constant errors showed significant positive directional biasing for interpolated acts greater than criterion positions. Further analyses at the 40-and 65-sec. retention intervals supported a recency interpretation. As the retention interval increased, the positive constant error was maintained for interpolated acts with the same post-biasing interval, whereas constant error became increasingly negative as the post-biasing interval increased. Examination of variable error revealed a slight increase over time and no significant differences between directional conditions. The recency findings were discussed in terms of the view that reproduction of a criterion act is dependent on the relative decay states between the interpolated and criterion traces.     

The Effect of Interpolated Motor Activities in Short-Term Motor Memory

This experiment examined the effect of an interpolated motor response on short-term retention of a blind positioning movement. The interpolated response was varied in degree of similarity to the response length (± 25, ± 50, and ± 100 mm.), in number of repetitions (0, 1, or 5), and in temporal position (immediate or delayed), with a retention interval of 25 sec. Absolute error was not affected but a systematic change in response bias due to interpolated motor activity was found. When an interpolated response was longer than the response length, the tendency to undershoot decreased. The defay of the interpolated response was relatively more important than the number of repetitions in producing a positive shift in response bias. These results are interpreted as evidence for a form of interference in short-term motor memory.     

Embodied grounding of memory: Toward the effects of motor execution on memory consolidation

Behavioural and neuroscientific research has provided evidence for a strong functional link between the neural motor system and lexical–semantic processing of action-related language. It remains unclear, however, whether the impact of motor actions is restricted to online language comprehension or whether sensorimotor codes are also important in the formation and consolidation of persisting memory representations of the word's referents. The current study now demonstrates that recognition performance for action words is modulated by motor actions performed during the retention interval. Specifically, participants were required to learn words denoting objects that were associated with either a pressing or a twisting action (e.g., piano, screwdriver) and words that were not associated to actions. During a 6–8-minute retention phase, participants performed an intervening task that required the execution of pressing or twisting responses. A subsequent recognition task revealed a better memory for words that denoted objects for which the functional use was congruent with the action performed during the retention interval (e.g., pepper mill–twisting action, doorbell–pressing action) than for words that denoted objects for which the functional use was incongruent. In further experiments, we were able to generalize this effect of selective memory enhancement of words by performing congruent motor actions to an implicit perceptual (Experiment 2) and implicit semantic memory test (Experiment 3). Our findings suggest that a reactivation of motor codes affects the process of memory consolidation and emphasizes therefore the important role of sensorimotor codes in establishing enduring semantic representations.     

The Effects of Hippocampal and Area Parahippocampalis Lesions in Pigeons: I. Delayed Matching to Sample

Four experiments were conducted to determine the effects of bilateral damage to the hippocampus and area parahippocampalis (Hp-APH) on visual memory in pigeons using the delayed matching-to-sample (DMS) procedure. In Experiment 1, we generated visual retention gradients with delays of 0, 1.5, 3, 6, and 12 sec both preoperatively and postoperatively in three pigeons with considerable preoperative visual DMS experience. Bilateral Hp-APH lesions had no effect whatsoever on visual retention. In Experiment 2, we examined the effects of Hp-APH lesions on both the acquisition of a visual DMS task with a 0-sec delay, and the subsequent retention performance with delays of 0, 3, 6, 12, and 24 sec. There was no difference between unoperated control pigeons and Hp-APH pigeons either in terms of the number of sessions required to learn the visual DMS task or in terms of their subsequent visual retention performance levels. In Experiments 3 and 4, we examined whether Hp-APH pigeons might be more sensitive than control pigeons to the effects of proactive interference (by reducing the duration of the intertrial interval) and retroactive interference (by introducing delay-interval illumination). Although reducing the duration of the intertrial interval and increasing the level of delay-interval illumination both resulted in lower performance levels on the visual DMS task, there was no indication that the Hp-APH pigeons were any more affected by the changes in interference levels than were unoperated control pigeons. These findings support the view that the Hp-APH in pigeons plays little role in the processing and retention of purely visual information.     

Short-term memory for time intervals

The effect of intertrial interval, preset interval, and retention interval on the performance of rats in a time estimation task was described. On each trial a signal was presented for a duration of 2 to 8 sec. Eighteen rats were trained to press one lever (the short response) if the signal was shorter than 4 sec, and another lever (the long response) if the signal was longer than 4 sec. When trials were massed (Experiment 1), the percentage long response was affected by the classification of the previous signal, but not by its actual duration. This suggests that the animals remembered the response made on the previous trial, but not the signal duration. If a response was not permitted on the previous trial (Experiment 2), the duration or classification of the previous signal had no effect on performance. This supports the conclusion from the first experiment and suggests that an animal can reset its internal clock in less than 2 sec. In Experiment 3, the difference limen of the psychophysical function increased with the duration of the retention interval, but the point of subjective equality did not change. This suggests that resetting of the internal clock occurs on a non-time dimension.     

Acquisition and retention of active avoidance behavior in previsual rats

The ability of previsual rats to acquire and retain an active avoidance response at intervals ranging from 0 min to 48 hr was examined in five experiments. Experiments 1 and 2 demonstrated that improvement in avoidance responding over trials was a training effect. Experiments 3 and 4 demonstrated that there was no evidence of retention of the avoidance response over retention intervals ranging from 15 min to 48 hr. Testing at intervals of 0-30 min in Experiment 5 indicated that 10-day-old rats could retain the response over intervals ranging from 0-15 min, but not over a 30-min interval. However, even at the very short intervals (5-15 min), there was evidence of a retention deficit. In general, the results suggest that previsual rats have sufficient memory capabilities to acquire an active avoidance response and to retain it over a 15-min interval. However, without intervention, e.g., reactivation, a retention deficit appears almost immediately, and retention loss seems complete within 30 min. This procedure and phenomenon may prove useful in allowing an immediate assessment of variables believed to alleviate retention loss and in eliminating the influence of many extraneous variables that could alter the retention performance of developing animals.     

Pupillary changes during encoding, storage, and retrieval of information.

6 subjects were each auditorily presented six lists of 7-digit numbers for retention intervals of 0, 5, and 10 sec. Pupil size was recorded during stimulus presentation, retention, interval, and recall of items. Results indicated that pupil dilation occurred during encoding and retrieval of stimulus items. Pupillary constriction was found during the retention interval when rehearsal was presumed to occur.     

Different gripping intervals in reproducibility of force-decreasing curve and muscle oxygenation kinetics during sustained maximal gripping

The purpose was to examine the properties and reproducibility of the force-decreasing curve and muscle-oxygenation kinetics measured by near infrared spectroscopy in sustained isometric grip and rhythmic repeated grip measurements using various contraction intervals (2 to 5 sec.). 10 healthy young adults performed both grip tests for 6 min., during which muscle-oxygenation kinetics were measured. The intraclass correlation coefficients of the time to reach the minimum value for oxygenated hemoglobin and myoglobin tended to become lower with longer relaxation time, especially over a 3-sec. interval. Although blood-flow obstruction closely influences the initial decreasing grip force during both grip tests with a 2-sec. interval, the decreasing grip force during rhythmic repeated gripping with over a 3-sec. interval is low. Hence, the physiological mechanism related to rhythmic repeated grip with over a 3-sec. interval may differ from that related to sustained isometric grip and rhythmic repeated grip with a 2-sec. interval.     

Programming time as a function of number of movement parts and changes in movement direction

The question of whether changes seen in simple reaction time (SRT) as a function of response complexity (i.e., number of movement parts) should be considered as differences in the time needed to centrally program a motor response was addressed. Using a large-scale tapping response, 14 subjects contacted from one to five targets positioned in a straight line, while a second group of 14 subjects executed 90 degrees changes in direction in striking the targets. Results revealed that mean SRT and mean premotor time increased linearly as the number of movement parts increased, regardless of whether changes in movement direction had to be programmed, with the greatest increase occurring between one-, and two-part responses. Increases in motor time were not sufficient to account for the sizeable SRT effect. These findings support the position of increased central programming time for more complex responses, and also help establish some of the boundaries of the complexity effect.     

Recognition memory: One-component strength functions In the “short-term to long-term transition region”

Experimental manipulationofthe upper bound on the retention interval (30 sec, with average duration of 11 sec, vs. 2 min, with average duration of 18 sec) failed to produce evidence for independent adjustment of initial long-term and short-term storage strengths. Very accurate strength functions of retention time were obtained; these were fitted equally well by a two-component equation and a one-componentequation derived from a theory postulating sequential employment of an active attentional buffer and a one-trace passive storage system. The latter theory appears to be capable of accounting for both post-attentional and two-phase experimental strength data, using fewer free parameters than strength theories which postulate the simultaneous existence of short-term and long-term traces. Other arguments for two traces are also discussed In relation to the postulate of a single post-attentional trace.