Right-ear advantage and delayed recall

Two studies were performed using monaural presentation of verbal material to test for a right-ear advantage (REA) in recall. It was hypothesized that a delayed recall task and examination of the serial position curve would be a more sensitive test for ear asymmetries than those used in previous studies. In Experiment 1, 30 right-handed male subjects were given lists of words to recall, presented to either the left or right ear, with language chatter, baroque music, or no stimulus concurrently presented to the opposite ear. Both immediate and delayed recall were assessed. The results indicated that the strongest REAs appeared in delayed recall. Moreover, the REAs occurred regardless of the stimulus conditions co-occurring in the other ear. Experiment 2 was done to test whether the REAs in the delayed recall were due to rehearsal biases. Twenty-four right-handed male subjects recalled lists of words with standard instructions and instructions to recall in the reverse order of input (limiting rehearsal). The results indicated that the backward instructions limited and controlled rehearsal and, hence, input to long-term storage; the REAs occurred in delayed recall under all instructional conditions.     

Accuracy of recognition for speech presented to the right and left ears

Earlier reports by other authors had shown that recall of dichotically presented speech was better for words arriving at the right ear, while recognition of passages of music was better for music presented to the left ear. It seemed desirable to test recognition for speech, in order to show that the difference between materials rather than the difference in testing techniques was responsible for this disparity between ears.

Accordingly 18 men were presented with dichotic lists of digits, and then tested for recognition of the digits. There was no indication of an advantage for the left ear, but rather of the advantage for the right already established for recall of speech materials.     

Emergence of unreported stimuli into imagery as a function of laterality of presentation: a replication and extension of research by Henley & Dixon (1974).

In Expt. 1, the research by Henley & Dixon (1974) was replicated. Two experimental groups (n=8 each) received subliminal words to the right ear and 8 min of music to the left ear or vice versa. Each group had its own control (n=8 each) with only music to one ear. Categorization and ranking of imagery reported, as well as performance on a checklist containing critical, associated, and non-related words, showed that emergence was greater with words to the right ear than with no words. There was no difference between experimental and control groups with words to the left ear. In Expt. 2, the music was eliminated, and subjects received subliminal words to the right ear (n=8) or no words. A significant difference between groups was found when the reported imagery was ranked as to emergence, and on the checklist, but not when the reports were categorized by judges.     

Coding processes in the free recall of associated word lists

An experiment is reported on the free recall of lists of 18 words. The lists consisted of words that were strongly or weakly associated to the eliciting stimulus, were members of either a single category or more than one category and were arranged into sets of three associated words or six associated words. Each list was presented once only and free recall required after a filled interval of 18 s. One half of the subjects were provided with cues at recall: the remainder were given no assistance. Recall efficiency increased with association level and with restricted category membership of the words in a set. Clustering at recall (when adjusted for opportunity) was greater in the 6×3 lists than in the 3×6 lists. The provision of cues only led to a significant facilitation in recall with lists consisting of 6 sets of 3 words. A detailed analysis of the recall data suggested the importance of the category membership variable in the production of the later recall.     

Shorter articles and notes grouping strategies with simultaneous stimuli

Broadbent (1956) reports that two lists of digits, each presented to one ear separately so that the items in the two series coincide in time, are grouped together according to the ear-of-arrival, and that these two lists are accordingly recalled separately, one after the other. To ascertain whether such a tendency reflected some built-in mechanism or whether it was due to an optional tactic, adopted through success in making sense of message sequences in other situations, an experiment was designed in which a meaningful message would emerge for the subject if the ear-of-arrival cue was ignored. In this experiment, words broken up into syllables, and phrases broken up into their monosyllabic constituent words were presented to the subject, with the constituents alternating between the two ears. At the same time lists of digits were presented to whichever ear was unoccupied. The results show that recall by meaning rather than by ear-of-arrival, when these are in conflict, can occur and is no less efficient.     

Dichotic listening in children: age-related changes in direction and magnitude of ear advantage

Children between the ages of 5 and 12 years were tested with dichotic listening tests utilizing single syllable words and random presentations of digits. They produced a higher prevalence of left ear dominance than expected, especially among right-handed children when tested with words. Whether more children demonstrate the LEA because of right hemisphere dominance for language or because there is less stability in ear advantage direction at younger ages cannot be fully resolved by this study. When ear advantages were measured by subtracting each child's lower score from the higher score without regard to right or left direction, an age-related trend toward lower measures of ear advantage was evident. This trend was greater for dichotic words than for dichotic digits. Structural factors that may be related to these results and possible influences of attention and verbal workload on the two kinds of dichotic stimuli are discussed.     

Does Global Context Modulate Cerebral Asymmetries? A Review and New Evidence on Word Imageability Effects

In this article we examine whether the distribution of function across the right and left cerebral hemispheres for lexical processing is influenced by the global context within which words are presented. A review of previously published studies indicates that the ubiquitous right visual field (RVF)/left hemisphere advantage for word recognition may be reduced or eliminated for nouns, content words, or high image words, but only when such items are presented along with verbs, function words, or low image words. However, paradoxically, when the former items are presented in more homogeneous contexts, the RVF advantage is uniformly observed. We propose that the processing efficiency of a hemisphere for a given stimulus depends on that item's relation to the other stimuli provided, that is, the global context. This was examined in a visual half-field experiment that varied whether high and low image nouns were presented in homogeneous (blocked lists) or heterogeneous (mixed lists) contexts. An unvarying RVF advantage was observed for high image words in homogeneous contexts, but this advantage was eliminated when the same items were presented in heterogeneous contexts. We suggest that stimulus heterogeneity maximizes reliance on differing, but complementary, computational biases across hemispheres. Hence, the extent to which the left and right hemispheres are recruited for the recognition of individual word types can vary dynamically with variation in the stimulus environment.     

Hemisphere differences in an auditory Stroop test

In an auditory Stroop test, right-handed subjects were required to judge the pitch of the following stimuli: two pure tones, one at a high frequency and one at a low frequency; two congruent words, “high,” sung at the high frequency, and “low,” sung at the low frequency; and two noncongruent words, “high” at low frequency and “low” at high frequency. A sequence of these stimuli was presented monaurally first to one ear, and then to the other. The Stroop effect (the difference between mean RT to congruent words, and mean RT to noncongruent words) was larger for right ear (left hemisphere) presentation. The same experiment was repeated dichotically with a competing message presented to the opposite ear. Again, the Stroop effect was larger for the right ear, and the ear differences were slightly more marked. The result is interpreted as reflecting hemispheric specialization for linguistic and nonlinguistic processing and a model of Stroop conflict in which response competition varies with the relative availability of the conflicting response.

     

Hemispheric asymmetry effects in children studied by dichotic listening and visual half-field testing

Dichotic listening (DL) and visual half-field (VHF) testing were used to study hemisphere asymmetry in a developmental perspective. Five-, 8-, and 11-year-old children were presented lists of fused words using a DL technique in Experiment 1, and 8- and 11-year-old children were presented pictures of common objects using a VHF technique in Experiment 2. In both experiments, measures of identification, free recall, and recognition of the words/pictures were employed. The results revealed effects of ear input (right-ear advantage) and half-field presentation (right visual half-field advantage) for all age groups, although the magnitude of this lateralization effect differed between the three memory measures. The results are discussed in relation to developmental aspects of language laterality, and in relation to the clinical utility of non-invasive lateralization techniques.     

Perceptual processing in dichotic listening.

Subjects heard two lists of 4 items each presented simultaneously to the two ears at a rate of four pairs of items per sec. A recall cue presented immediately after the test list signalled report of 4 of the 8 items. In recall by spatial location, the cue indicated whether the items on the right ear on left ear should be recalled. In recall by category name, the cue indicated the superset category (e.g., letters or words) of the items to be recalled. Recall by spatial location was not significantly different than recall by category name. This results argues against the idea of a preperceptual auditory storage that holds information along spatial channels for 1 or 2 sec. The final experiment showed that recall by spatial location is significantly better than recall by category name when the report cue is given before, not after, the list presentation. These results show that spatial location can be used to enhance semantic processing and/or memory of 1 of 2 simultaneous items, but only if the relevant location is known at the time of the item presentation.     

Norms for word lists that create false memories

Roediger and McDermott (1995) induced false recall and false recognition for words that were not presented in lists. They had subjects study 24 lists of 15 words that were associates of a common word (called the critical target or critical lure) that was not presented in the list. False recall and false recognition of the critical target occurred frequently in response to these lists. The purpose of the current work was to provide a set of normative data for the lists Roediger and McDermott used and for 12 others developed more recently. We tested false recall and false recognition for critical targets from 36 lists. Despite the fact that all lists were constructed to produce false remembering, the diversity in their effectiveness was large--60% or more of subjects falsely recalled window and sleep following the appropriate lists, and false recognition for these items was greater than 80%. However, the list generated from king led to 10% false recall and 27% false recognition. Possible reasons for these wide differences in effectiveness of the lists are discussed. These norms serve as a useful benchmark for designing experiments about false recall and false recognition in this paradigm.     

Can attention give a left-ear advantage for verbal stimuli?

Three independent groups of 8 subjects listened monaurally to a randomized list of 50 common and 50 rare words and responded ‘yes’ to rare words. Responses were analyzed for correct identifications of rare words. A 50:50 group heard an equal number of words in right and left ears and gave a small but non-significant right-ear superiority. A 66:34 group heard nearly twice as many words in the right ear as the left and gave a significant right-ear superiority. A 34:66 group heard nearly twice as many words in the left ear as the right and gave a significant left-ear superiority. Responses were also analyzed according to signal-detection theory. Implications are discussed for theories of ear advantages.     

Interference in memory for multiple contexts

Remembering that an item occurred in several different lists is formulated here in terms of retrieval of corresponding list tags associated to the item. Therefore, associative interference should operate upon remembering the several list contexts in which an item appeared. Experimental Ss studied four (or five) overlapping lists of 16 words, sampled from a master set of 32 words, with a given word exemplifying one of the 2 4 (or 2s 5 ) possible sequences of appearances and nonappearances over the four (or five) lists. Later Ss rated from memory for each word and for each list whether that word had occurred in that list. After correcting for interlist generalization effects, indices of discriminative memory revealed strong proactive interference and weaker retroactive interference. Discriminative memory that an item occurred in a given list was poorer the more prior or more subsequent lists in which that item had also occurred. Thus, list differentiation appears explicable in terms of item-specific associative interference.     

Good and bad effects of phonological similarity on word and nonword recall: The role of beginnings and ends

This study explored whether earlier results of differential (harmful vs. helpful) short-term memory effects of shared syllables at nonword beginnings compared to ends could be replicated for lists of bisyllabic real words. We studied immediate serial recall of lists that had phonologically redundant syllables at the beginnings or ends of two-syllable words or nonwords. The results showed that redundancy at the beginning had a negative effect on both types of material. Redundancy at the end did not impair memory for nonwords but harmed the serial recall of words. Irrespective of lexicality, lists of beginning-redundant items were more difficult to recall than end-redundant items. The distribution of errors suggested that the better recall of end-redundant lists compared to beginning-redundant lists was related to a positive effect at encoding and/or retention, independent of effects at recall, for both words and nonwords.     

Elimination of the word length effect by irrelevant sound revisited

The word length effect refers to the tendency for lists of long words to be recalled less well than lists of short words. Theoretical and empirical objections are raised to a recent claim that irrelevant speech eliminates the word length effect (Neath, Suprenant, & LeCompte, 1998). A first experiment using a within-subjects design of adequate power (N = 65) fails to replicate their finding, showing instead that the word length effect is not differentially eliminated by speech as opposed to tones. In a second experiment, the effect of change (repeated vs. changing sounds) is shown to be additive to the effect of word length for both speech and nonspeech. Irrelevant speech and irrelevant tones have comparable effects on lists of short or lists of long words. These results are at variance with the feature model (e.g., Nairne, 1990).     

The effects of attention on ear advantages in dichotic listening to words and affects

This study examined the effects of attention on ear advantages using dichotic listening to words and affects, a focused-attention paradigm. We compared the mixed condition, in which attention is switched between the ears in each trial, to the blocked condition, in which attention is directed to one ear for an entire block of trials. Results showed a decreased right ear advantage for word processing only in the mixed condition and an increased left ear advantage for emotion processing in both attention conditions for hits index. The mixed condition showed smaller laterality effects than the blocked condition for words with respect to hits index, while increasing right ear predominance for intrusions. The greater percentage of intrusions in the right ear for the word task and in the mixed condition suggests that the right ear (left hemisphere) is most vulnerable to attention switching. We posit that the attention manipulation has a greater effect on word processing than on emotion processing and propose that ear advantages reflect a combination of the effects of attentional and structural constraints on lateralisation.     

Right hemisphere comprehension of verbs in patients with complete forebrain commissurotomy: Use of the dichotic method and manual performance

The paradigm of dichotic listening was used to investigate verbal comprehension in the right, so-called “nonverbal,” hemisphere. Verbal commands were presented to the right and left ears in the simultaneous (dichotic) paradigm. There were striking instances, especially when the left hemisphere was occupied with some extraneous task, in which the right hemisphere understood the verbal command and executed the appropriate motor responses. In those instances the left hemisphere gave no overt response. Although the left hemisphere was usually dominant, it can be nevertheless concluded that not only can the right hemisphere understand verbal commands but can also express itself manually by executing actions more complex than object retrieval or pointing. As has been known for some time, the blockage of the ipsilateral pathway seems so complete during dichotic listening in the commissurotomy patient that there is no report of the words in the left ear—only of those presented to the right. At the same time there is normal report when words are presented to the left ear alone. It was found in the present study, however, that this model is too simple and only applies to the verbal response paradigm of dichotic listening. Under circumstances of dichotic presentation where the stimulus in the left ear (ipsilateral pathway) is necessary or important to the left hemisphere for completing a task, words from both pathways are reported. One may conclude that there exists a gating mechanism in each hemisphere that controls the monitoring of each auditory pathway and the degree of ipsilateral suppression.     

Dichotic listening in a child recovering from acquired aphasia

A right-handed 6-year-old boy with acquired aphasia of left-hemisphere origin was investigated with various dichotic listening tasks 8 and 13 months after onset of the symptoms. Total right ear extinction was found repeatedly using both numbers and words as stimuli. Furthermore, magnitude of right ear extinction was not amenable to modification through verbal training, but disappeared when words were presented to the child's right ear with simultaneous white noise to the left ear. The findings are discussed in terms of the plasticity of cerebral dominance during childhood.     

Hemispheric equality in reaction times to emotional and non-emotional nouns

Twenty presentations of 6 emotional and 6 non-emotional words in mixed random orders were monaurally presented to the right or left ear. Using the left hand, subjects pushed one of two response buttons indicating type of word heard. Performance improved in later trials and emotional words were recognized more quickly regardless of ear presentation. No differences were associated with the separate ear presentations. Equivalent hemispheric performance indicates equal processing sensitivity to four-letter emotional and non-emotional nouns and substantiates the right hemisphere's verbal processing capability for simple nouns.     

Verbal and affective laterality effects in P-dyslexic, L-dyslexic and normal children.

Lateralization of verbal and affective processes was investigated in P-dyslexic, L-dyslexic and normal children with the aid of a dichotic listening task. The children were asked to detect either the presence of a specific target word or of words spoken in a specific emotional tone of voice. The number of correct responses and reaction time were recorded. For monitoring words, an overall right ear advantage was obtained. However, further tests showed no significant ear advantage for P-types, and a right ear advantage for L-types and controls. For emotions, an overall left ear advantage was obtained that was less robust than the word-effect. The results of the word task are in support of previous findings concerning differences between P- and L-dyslexics in verbal processing according to the balance model of dyslexia. However, dyslexic children do not differ from controls on processing of emotional prosody although certain task variables may have affected this result.