Source variability and recall of auditory material 1

Recall of auditory narrative material was measured under three conditions of presentation. These were a single source condition with material from one speaker, a four source fixed sequence condition with material from four speakers in a fixed sequence of 3-sec. lengths, and a four source random condition with material from four speakers in a random sequence of 3-sec. lengths. Recall was better for the single source condition than for the four source conditions. No significant difference was found between the fixed and random sequential presentations. Results are discussed in terms of the attentional behaviors involved in the tasks.     

The retention of imagined and seen spatial matrices

The nature of imagery and its relationship to perception were probed by having students recall the contents of 4 × 4 spatial matrices after they constructed the matrices through processes of imagery, seeing, or verbal coding. In the imagery and verbal conditions, students listened to auditory messages which described the matrices. Students in the imagery condition were instructed to imagine the matrix being described; students in the verbal condition received no imagery instructions; and students in the seeing condition saw the matrix for an inspection period prior to recall. Recall was best when students saw the matrices, intermediate in the imagery situation, and poorest in the verbal situation. Recall was best for the corner cells of seen and imagined matrices, indicating the spatial nature of these processes; no such effect was found for verbal processing. Forgetting over a 10-sec interval occurred only for verbal processing. Implications for understanding the nature of visual imagery and perception are discussed.     

Rehearsal strategies and the serial-position curve in immediate free recall of ordered items

Immediate free recall of random strings of 10 numbers was studied under four experimental conditions: as each number was presented, subjects either had to recall the previous number (Recall n-1), recall the number just presented (Recall n), read the number (Read aloud), or were silent (Free Recall). Overall recall was the same in all conditions. Recall and order of recall by serial-position changed systematically, with an increasing recency and decreasing primacy effect from Free Recall through Read Aloud and Recall n to Recall n-1. These changes in recall order and serial-position curves suggest that differential rehearsal of items is decreased by requiring retrieval during presentation.     

Memory for movement: Interaction of location and distance cues and imagery ability

The present experiments examined the role of imagery ability in recall of either the terminal location or the distance of a preselected horizontal linear movement following changes in the recall starting position. Subjects were selected on the basis of their scores on a shortened version of the Betts Questionnaire upon Mental Imagery (Betts Q.M.I., Sheehan 1967). Both high and low imagers were assigned to one of four groups, HIL, LIL, HID, LID, the last letter indicating the movement cue (terminal location or distance moved) to be recalled. Recall of the appropriate movement cue from one of four new recall starting positions occurred after either a 5-sec or 30-sec unfilled retention interval. Analysis of constant error indicated all groups were unable to recall the specified movement cue independent of the other source of information, even when subjects were given explicit instructions to utilise an imagery strategy. The data corroborate our earlier findings that memory for self paced movements is based on an interaction of location and distance cues derived from the criterion movement.     

Multiple coding strategies in the retention of musical tones by possessors of absolute pitch

Eighteen musicians with absolute pitch (AP) confirmed by screening tests participated in tonal and verbal short-term-retention tasks. In the tonal task, subjects identified three successive piano tones by their letter names. Recall of these note names after 18 sec of counting backwards was near perfect. Recall after an 18-sec delay filled with random piano tones was also near perfect. In contrast, the same subjects demonstrated significant forgetting when required to retain letter trigrams while counting backwards for 18 sec. These results were essentially replicated in a second experiment using longer (27 sec) retention intervals, a more demanding verbal interference task, and an active musical interference task (singing a descending scale). We interpret these results as indicating that retention of note names by possessors of AP is not limited to verbal encoding; rather, multiple codes (e.g., auditory, kinesthetic, and visual imagery) are probably used.     

Interference processes in monkey auditory list memory

A rhesus monkey’s memory was tested for single items and four-item lists of natural and environmental sounds. Memory items were presented from a center speaker, followed by a retention delay and then a choice response to a test sound presented simultaneously from two side speakers. Recognition of the last item of four-item lists was much poorer than that of single items at 0-, 1-, and 2-sec delays, despite there being the same temporal relations between study and test. This result showed that the first three items proactively interfered with memory of the last list item. Proactive interference dissipated after 2 sec, revealing a recency effect that eventually equaled single-item performance. Recognition of the first item of four-item lists was much poorer than single items at 20- and 30-sec delays, showing that the last three items retroactively interfered with memory of the first list item. The results point to the critical nature of interference processes in the understanding of serial position functions.     

COMPARISON OF EXTINCTION,DRO 0-SEC,AND DRO 6-SEC IN THE ELIMINATION OF IMITATIVE RESPONDING UNDER DISCRETE-TRIAL PARADIGMS1

Imitative response levels were observed for normal 5-yr-old children within a discrete-trial imitation paradigm. Following imitation training sessions, children were observed under conditions of contingent reinforcement for three experimental sessions. Following the contingent reinforcement phase, children were then observed under reversal conditions for four sessions. A 3 × 4 repeated measures design was employed for observing response decrements under conditions of extinction, DRO 6-sec, and DRO 0-sec. The DRO 0-sec group demonstrated a significantly greater decrement in imitative responding than did the DRO 6-sec and extinction group. The differences in effects between the two DRO conditions and results from previous studies in which DRO procedures have had little effect in reducing imitative responding, suggest an incomplete understanding of the ways in which DRO procedures may operate.     

Influence of motion on face recognition

The influence of motion information and temporal associations on recognition of non-familiar faces was investigated using two groups which performed a face recognition task. One group was presented with regular temporal sequences of face views designed to produce the impression of motion of the face rotating in depth, the other group with random sequences of the same views. In one condition, participants viewed the sequences of the views in rapid succession with a negligible interstimulus interval (ISI). This condition was characterized by three different presentation times. In another condition, participants were presented a sequence with a 1-sec. ISI among the views. That regular sequences of views with a negligible ISI and a shorter presentation time were hypothesized to give rise to better recognition, related to a stronger impression of face rotation. Analysis of data from 45 participants showed a shorter presentation time was associated with significantly better accuracy on the recognition task; however, differences between performances associated with regular and random sequences were not significant.     

EFFECTS OF ALTERNATIVE REINFORCEMENT: DOES THE SOURCE MATTER?1

In a chamber with a single response key, pigeon's key pecks were reinforced with food according to a variable-interval schedule. In addition, extra reinforcements occurred concurrently according to an independent schedule. In one condition, availability of the extra reinforcements was signalled by a change in key color from white to red. The extra reinforcements occurred after a peck on the red key. In a second condition, the extra reinforcements were unsignalled and occurred only after a 2-sec pause in pecking for one group of subjects and were unsignalled and occurred freely as scheduled for another group of subjects. In the first two conditions, duration of reinforcement was varied. A third condition duplicated the second but varied rate rather than duration of reinforcement. The rate of pecking varied inversely with the amount of extra reinforcement per unit time according to the same function, regardless of the condition regulating occurrence of the extra reinforcements, and regardless of whether or not a 2-sec pause was required for their occurrence. The shape of this function was predicted by Herrnstein's (1970) matching law.     

The influence of the acoustic context on vertical sound localization in the median plane

The influence of background sounds (frames) on vertical localization of single sound sources (targets) was examined in four experiments. Loudspeakers (five targets and four frames) were positioned in the median plane, ranging from +30 degrees to -30 degrees above and below the subject's ear level. The subjects determined the vertical position of the targets by either verbal judgments or manual pointing. Frame and target sounds were presented concurrently or successively with a 1-sec interval; both consisted of (1) 300-Hz square waves, (2) noise, or (3) targets of noise and frames of 300-Hz square waves. Particularly in the second condition, the subjects consistently shifted the apparent target positions away from the frame locations. This contrast effect persisted even 1 sec after the offset of the frames. No effect was found with different waveforms for the frame and the target. Results are related to recent findings indicating a similar effect in the azimuthal dimension. Possibly the effect is based on a mechanism in which the auditory system adapts to recently heard sound source positions.     

Developmental changes in free recall: The interaction of task structure and age

Free-recall learning and organization were measured for 3rd, 7th, and 11th graders under conditions which varied the type and amount of task structure. Task structure for the input or list-presentation phase was manipulated by using a random, constant, or alphabetic item sequence across trials. Task structure for the output or recall phase was manipulated by providing standard instructions or instructions which suggested the possible use of an alphabetic ordering scheme. Recall performance and organization showed an interaction between age and both manipulations of task structure. The 3rd graders required the maximal amount of task structure (alphabetic order with alphabetic instructions) to demonstrate recall facilitation relative to the completely unstructured control condition. The 7th graders showed recall facilitation for intermediate and high levels of task structure, and the 11th graders showed recall facilitation for low, intermediate, and high levels of task structure. The results are related to current hypotheses about developmental changes in recall performance and their relationship to changes in the systematic use of organizational strategies.     

Comparing Verbal and Reaching Responses to Visually Perceived Egocentric Distances

Ability to visually perceive egocentric target distance was assessed using 2 response measures: verbal reports and reaches. These 2 response measures were made within experimental trials with the participants' eyes closed either immediately after viewing the target (Experiment 1) or after a 6- or 12-sec delay (Experiment 2). Systematic and random errors differed as a function of the response measure. The random errors for the verbal reports and the reaches were not correlated in the no-delay condition but became correlated in each of the 6- and 12-sec delay conditions. Systematic errors varied as a function of delay for the verbal reports but not for the reaches. These findings suggest that immediate verbal and action responses are not directed by a single internally represented perceived depth, as suggested by Philbeck and Loomis (1997). The findings are related to the possibility of separate neurological streams for vision (e.g., Bridgeman, 1989; Milner & Goodale, 1995; Rossetti, 1998), and our discussion contains a review that supplements Michaels's (2000) commentary on those theories. The findings are also related to the recent theories regarding task-specific devices, and a possible synthesis of task-specific devices and separate visual streams is offered.     

Immediate and delayed recognition of sequentially presented random shapes.

Two experiments tested whether short-term memory accounts for the recency effect observed with rapid sequential presentation of nonverbal stimuli. Four random shapes were presented sequentially (with no interstimulus interval) on each trial at rates of 150 msec, 250 msec, 500 msec, and 1,000 msec per stimulus. Subsequent recognition varied positively with exposure duration, ranging from 57% at 150 msec to 77% at 1,000 msec. Two serial position effects were observed: a slight decrease in recognition accuracy for the first stimulus in each sequence and a large increase in recognition for the last stimulus in each sequence. The recency effect was not altered by an intervening 30-sec delay, an intervening 30-sec copying task, or an intervening 30-sec copying and counting task. Since neither visual nor verbal distractors altered recognition accuracy, it was suggested that all shapes were processed directly into long-term memory storage. It also was hypothesized that long-term storage of a nonverbal stimulus requires identification of a distinctive feature of the stimulus and that this process may continue for a brief period after actual stimulus offset.     

Temporal factors influencing performance in the missing scan paradigm

Sixty Ss were each presented 120 random sequences of 9 of the 10 digits (0–9); their task on each trial was to supply the missing digit. Two stimulus input rates and two response time limits were combined factorially to yield four experimental conditions. Contrary to expectation, evidence seeming to support the use of a strategy based on the ordinal properties of the stimuli was found only when rapid (1-sec) responses were required, regardless of input rate. It is suggested that this result is most reasonably attributed to the operation of a guessing bias for numbers in the middle of the ordinal sequence. Differences in the constitution of the stimulus series may account for the failure to confirm previous findings of an ordinal strategy.     

Temporal contiguity and the judgement of causality by human subjects

Three experiments examined the role of the degree of temporal contiguity between an action and an outcome in human causality judgement. In all the experiments subjects were required to perform an action—pressing a key on a computer keyboard—and to judge the extent to which the action caused an outcome on the computer screen to occur. The action and outcome occurred on a free-operant schedule. In the first experiment a 2-sec delay between the action and outcome reduced causality judgements relative to a situation in which there was no delay. In the second experiment judgements in conditions with delays of 0, 4, 8, and 16 sec were compared with judgements in conditions in which the same pattern of outcomes occurred non-contingently with respect to the subjects' responding. In both of these experiments the events were controlled by random ratio schedules, following the procedure of Wasserman, Chatlosh, and Neunaber (1983), in which each condition was divided into 1-sec intervals. In the third experiment judgements in conditions with delays of 0, 2, 4, or 8 sec were compared in a continuous procedure rather than one divided into 1-sec intervals. In all experiments the increasing delays led to progressively lower judgements of causality. The results are related to three accounts of the mechanism underlying human causality judgement and are also compared with results from analogous animal conditioning studies.     

Developments in source monitoring: the role of thinking of others

Adults' source judgments are more accurate when they focus on speakers' emotions than when adults focus on their own emotions. Focusing on speakers may lead to better source memory because it encourages processing of the perceptual characteristics of the source and binding of that information to the content of what is being said. The purpose of the current work was to evaluate whether young children's source memory similarly benefits from this outward encoding focus and whether this effect changes developmentally. In Experiment 1, when 4- and 5-year-olds heard an audiotape of two dissimilar speakers, only the 5-year-olds showed better source memory when asked to adopt an other-focus. In Experiment 2, when 4- and 5-year-olds watched a videotape of two similar speakers, the same pattern was found. However, in Experiment 3, when 4-year-olds watched a videotape of two dissimilar speakers (a more optimal encoding condition in which 5-year-olds showed ceiling performance), 4-year-olds benefited from taking an other-focus during encoding. Overall, the data suggest that the benefit for source memory of focusing on another person develops over the preschool years.     

Behavioral variability and frequency-dependent selection.

In Experiment 1, two conditions were compared: (a) a variability schedule in which food reinforcement was delivered for the fourth peck in a sequence that differed from the preceding N four-peck sequences, with the value of N continuously adjusted to maintain reinforcement probability approximately constant; and (b) a control condition in which the variability constraint was dropped but reinforcement probability remained constant. Pigeons responded approximately randomly under the variability schedule but showed strong stereotyped behavior under the control condition. Experiments 2 and 3 tested the idea that variability is the outcome of a type of frequency-dependent selection, namely differential reinforcement of infrequent behavior patterns. The results showed that pigeons alternate when frequency-dependent selection is applied to single pecks because alternation is an easy-to-learn stable pattern that satisfies the frequency-dependent condition. Nevertheless, 2 of 4 pigeons showed random behavior when frequency-dependent selection was applied to two pecks, even though double alternation is a permissible and stable stereotype under these conditions. It appears that random behavior results when pigeons are unable to acquire the stable stereotyped behavior under a given frequency-dependent schedule.     

Developmental differences in recall: Encoding or retrieval?

First- and fifth-grade children and college adults (ages 6, 10, and 18 years, respectively) were presented a 30-item set of pictures to recall in a 4-trial study-test procedure. The stimuli were presented in one of three ways (encoding condition): randomly, blocked (according to categories), or sort (the subject was given the stimuli in random order and asked to sort them into categories). Recall was either free, cued, or constrained (retrieval condition). Results indicated that maximum adult recall was a function of the interaction of encoding and retrieval conditions, and that first- and fifth-grader's recall was influenced by retrieval conditions but not by encoding conditions. The blocked and sort encoding conditions did result in increased clustering relative to random encoding at all three ages, however. It was concluded that encoding conditions influence recall only as they effect the use of retrieval strategies.     

Backward associative strength determines source attributions given to false memories

Source attributions for falsely remembered material were investigated in two experiments. A male and a female speaker each presented either an entire word list or half of the items from each of multiple Deese-Roediger-McDermott (DRM) lists commonly used in this paradigm. In the latter condition the tendency of each list half to activate a nonpresented, critical list theme item was manipulated. All of the list halves differed in backward associative strength (BAS), and each was presented by one or the other of the two speakers. In these correlated conditions, when critical items were falsely recognized (Experiments 1 and 2) or recalled (Experiment 2), source attributions were more frequently made to the speaker of the list items with the higher average BAS. This source attribution effect appears to result from the binding of list item source characteristics to activated critical items during encoding, as opposed to being the result of a biased retrieval process. The results are interpreted as consistent with an activation/monitoring account of false memory in the DRM paradigm.     

Control of pigeons' matching-to-sample performance by differential sample response requirements

Pigeons were trained on a matching-to-sample task in which sample hue and required sample-specific observing behavior provided redundant, relevant cues for correct choices. On trials that involved red and yellow hues as comparison stimuli, a fixed-ratio 16 schedule (FR 16) was required to illuminate the comparisons when the sample was red, and a differential-reinforcement-of-low-rates 3-sec schedule (DRL 3-sec) was required when the sample was yellow. On trials involving blue and green hues as comparison stimuli, an FR 16 schedule was required when the sample was blue and a DRL 3-sec schedule was required when the sample was green. For some pigeons, a 0-sec delay intervened between sample offset and comparison onset, whereas other pigeons experienced a random mixture of 0-sec and 2-sec delay trials. Test trial performance at 0-sec delay indicated that sample-specific behavior controlled choice performance considerably more than sample hue did. Test performance was independent of whether original training involved all 0-sec delay trials or a mixture of 0-sec and 2-sec delays. Sample-specific observing response requirements appear to facilitate pigeons' matching-to-sample performance by strengthening associations between the observing response and correct choice.