Associative and categorical hypotheses of organization in the free recall of adults and children

Associative and categorical explanations for the organization children and adults display in free recall were tested. It was expected that young children would show output clustering as a function of associations between individual items within categories rather than relationship to the taxonomy itself. Kindergarten, fourth-grade, and tenth-grade subjects were presented with pictures representing the four factorial combinations of high and low interitem association and high and low category relatedness. Each set of pictures could be divided into four taxonomic categories of six items each. Kindergarteners displayed greater category clustering of highly associated items than weak associates. Older subjects showed sensitivity to both organizational dimensions. These data support a hypothesis that young children cluster in recall as a function of associations while older individuals show organizational flexibility which serves to facilitate greater recall.     

Facilitation of instrumental behavior by a Pavlovian appetitive conditioned stimulus

Three experiments examined appetitive Pavlovian-instrumental interactions by presenting separately trained conditioned stimuli (CSs) during reinforced instrumental responding in rabbits. Intra-oral reinforcement was used to minimize interference from peripheral responses such as magazine approach. In experiment 1, the rabbits were first trained to perform an instrumental head-raising response for sucrose reward. A conditioned jaw movement response was then established to a 2-sec CS by pairing it with sucrose; a control stimulus was unpaired with sucrose. Instrumental responding maintained by a variable-interval 40-sec schedule was enhanced during 10-sec presentations of the paired, but not the unpaired, CS. Responding on a variable-ratio 15 schedule was unaffected except on trials on which the pre-CS baseline response rate was low; in such cases the paired CS caused a long-lasting acceleration of responding. Noncontingent presentation of the sucrose reinforcer itself briefly suppressed responding but had no long-term effect. In Experiment 2, a CS that had been conditioned at a 10-sec duration produced the same pattern of effects as in the first study, indicating that facilitation resulted from CS presentation rather than from the frustrative effects of non-reinforcement of the CS. In Experiment 3 an inhibitory CS blocked facilitation by the excitatory CS but did not itself affect instrumental responding. These results support the view that Pavlovian processes play a positive role in instrumental performance and suggest that previous findings of suppression by a short-duration CS reflect peripheral interference. The dependence of facilitation on the baseline level of responding is discussed in terms of associative and motivational theories of Pavlovian mediation.     

Facilitation of recall with intralist cues: Time-dependent characteristics of cued recall

List items were given as retrieval cues in a free-recall experiment which factorially combined the presence or absence of cues with the amount of time allowed for use of each cue (10 sec or 30 sec). A categorizable list of 75 randomly presented words was learned, and 48 h later a free-recall test trial was given, followed by a final memory search task. During the final task, cued subjects received words from categories that had not been recalled during the free-recall test. With both time intervals, cued subjects recalled more words than noncued subjects, indicating that random presentation of categorized words does not necessarily preclude the observation of a cueing effect with list items, as has been reported previously. The composition of recall, whether from previously recalled or nonrecalled categories, varied as a function of time for both groups. The results were interpreteod in terms of retrieval strategies employed by cued and noncued subjects and the effect of time on these strategies.     

Clustering by aphasics in free recall

Aphasic performance was compared to normal and left hemiplegic controls in the use of clustering to aid recall of a list of words in a multitrial free recall experiment. Use of clustering correlated with increased recall scores. Left hemiplegic performance was superior to aphasic and inferior to normal suggesting that the presence of brain damage decreased clustering but that this decrease was greater in the presence of aphasia. A second experiment examined the possibility of remediating aphasic clustering behavior by providing cues as a training device. Cues, which aided normals, did not benefit the majority of aphasics. Results are interpreted in terms of their relationship to cognitive functioning.     

Redundancy gain for categorical targets depends on display configuration and duration

Redundancy gain is an improvement in speeded target detection when the number of targets associated with a single response is increased within a single display. The effect has been clearly demonstrated with specific targets, but it is not clear if it occurs in categorization tasks with non-identical targets. The current study tested the effect of target redundancy on speed and accuracy in a go/no-go categorization task. Targets were digits tilted 45° to the left, and were displayed in unilateral, bilateral, or central displays for either 1500?ms or 100?ms. Redundancy gain only occurred for brief targets displayed bilaterally in the upper visual field. The results indicate that redundancy gain is possible for categorization tasks with some bilateral configurations, supporting a role for interhemispheric processing in redundancy gain. Additionally, the results may indicate that processing strategies mask redundancy gain when participants can view targets for a long period of time.     

Effect of changing the unconditioned stimulus on appetitive blocking

In four experiments we examined the effects of changing the unconditioned stimulus (US) on appetitive blocking. In Experiments 1A, 1B, and 2 we established that substituting food for water, or water for food, in the compound stage did not attenuate blocking relative to groups that received the same US throughout conditioning. Experiment 3 showed that satiation with the US used prior to compound conditioning with a different US does not affect blocking. Experiment 4 revealed that changing the location of US delivery, as well as the quality of the US, also leaves blocking unaffected. It is suggested that these results demonstrate that blocking occurs, provided that there is no change in the affective properties of the US.     

Blocking by fixed and variable stimuli: Effects of stimulus distribution on blocking

An experiment with rats compared the ability of fixed and variable duration cues to produce blocking. Rats in group B (Blocking) were trained that both fixed- (F) and variable- (V) duration cues would be followed by food delivery. In a subsequent training stage F and V continued to be reinforced, but F was accompanied by X, and V by Y. In the test phase responding to X and Y was examined. Control group O (Overshadowing) received identical treatment, except that F and V were nonreinforced in the first training stage. In group B there was evidence for blocking, but only of X, which had been conditioned in compound with the fixed-duration F; there was no evidence for blocking of Y, which had been conditioned in compound with the variable-duration V. It is suggested that this result may occur because fixed cues reach a higher, more stable asymptote of associative strength than do their variable equivalents.     

The anatomy of free recall

The relative importance of various covert cues used in free recall is inferred on the basis of conditional probabilities of free recall given success vs failure of cued recall of the same material. Thirty-six names associated with pictures arranged in a 6 by 6 matrix were learned. A free recall test of names was followed by cued recall of names, with pictures, positions, or joint pictures and positions used as cues. Matching tests based on these cues were also administered. The tests were given at one of two stages of training, immediately or after 2 days. Pictorial and position cues are equally well encoded, but pictorial cues are less accessible and, therefore, relatively more useful in cued recall than in free recall. Position and pictorial information related to the names appears to be encoded and forgotten independently, and there is no evidence for summation of subthreshold encoding effect.     

Association and categorisation effects on free recall

Lists of 18 words which varied in mean associative strength, the category membership of the associations and in word frequency were presented to subjects 3 times with recall required after each presentation. Recall efficiency increased with association level and with similarly categorised associates. In lists of High mean associative strength which consisted of similarly categorised words, the recall of high frequency word lists was facilitated but at low levels of associative strength, with similarly categorised words, recall was facilitated at both levels of word frequency used. Clustering and errors which were associatively related to the items being learned were greater in lists which contained sets of similarly categorised associates.     

Neurophysiological indices of free recall memory biases in major depression: The impact of stimulus arousal and valence

This study examined differential impact of the valence and arousal characteristics of stimuli on memory biases and brain activity in major depressive disorder (MDD) and non-depressed control participants. P300 and slow wave (SW) components of the event-related brain potential (ERP) were recorded in 18 MDD and 18 control individuals during the encoding of positive and negative, high and low arousal words in a free recall task. Control participants demonstrated expected enhanced memory for positive stimuli that was accompanied by a corresponding increase in SW ERP components. These effects were not seen in the MDD participants. Rather, memory biases for negative information in MDD were only observed for low arousal words and were not reflected in ERP amplitudes. This study suggests that the inconsistency in the MDD memory bias literature may be related to the arousing nature of the stimuli incorporated in the study.     

Valence-specific laterality effects in vocal emotion: interactions with stimulus type, blocking and sex

Valence-specific laterality effects have been frequently obtained in facial emotion perception but not in vocal emotion perception. We report a dichotic listening study further examining whether valence-specific laterality effects generalise to vocal emotions. Based on previous literature, we tested whether valence-specific laterality effects were dependent on blocked presentation of the emotion conditions, on the naturalness of the emotional stimuli, or on listener sex. We presented happy and sad sentences, paired with neutral counterparts, dichotically in an emotion localisation task, with vocal stimuli being preceded by verbal labels indicating target emotions. The measure was accuracy. When stimuli of the same emotion were presented as a block, a valence-specific laterality effect was demonstrated, but only in original stimuli and not morphed stimuli. There was a separate interaction with listener sex. We interpret our findings as suggesting that the valence-specific laterality hypothesis is supported only in certain circumstances. We discuss modulating factors, and we consider whether the mechanisms underlying those factors may be attentional or experiential in nature.     

Young children produce categorical false recall without activation of the lure items

Individuals who study a list of words that are all related to another word that is not presented (a lure word) sometimes produce a false memory of having studied the lure word. The false memories are observed in lists of words that are in the same category as (category list) or associated with (associative list) a word that was not presented in an attempt to elicit false recall. The present study investigated whether young children create these types of false recall. Following the study of a categorical list, false recall was elicited in young children to the same degree as in adults, but studying an associative list elicited false recall only in adults. Furthermore, categorically related lure words did not have a priming effect in young children. These results suggest that the categorical false recall is produced via a different mechanism from the associative false recall.