An adult model of preschool children’s speech memory

In previous work, it has been demonstrated that phonetic similarity among the items in a spoken list interferes with recall much more in school-aged children than in preschool children. The basis of this developmental change, however, is unclear. In the present study we examined the possibility that a developmental increase in the use of covert verbal rehearsal accounts for the change in the effects of phonetic similarity. Adults who recalled lists of spoken words during articulatory suppression tasks that blocked covert rehearsal were found to display patterns of recall that resembled those ordinarily found in 5-year-old children. The specific aspects of rehearsal responsible for these effects also were investigated.     

The development of organized rehearsal

The purpose of this research was to evaluate the development or organization strategies in rehearsal processes. First-grade (age 7 years), third-grade (age 9 years), and fifth-grade (age 11 years) children were exposed to a memory task which involved multiple overt rehearsal and recall phases. The children were either free to rehearse any words from a taxonomically structured list or they were taught to rehearse in categories. The recall phase was either free or categorically cued. The number of repetitions in rehearsal increased only as a function of age. All of the independent variables facilitated the amount of organized rehearsal and the amount of retention. Children at all ages were able to maximize the relative amount of organized rehearsal when rehearsal was cued. The correlational analysis of the dependent variables indicated that for young children the quantity of rehearsal was linked to retention, but for older children the quality of rehearsal was related to retention. The results were interpreted as demonstrating the bases for production inefficiencies.     

Specificity of memory representations for spoken words

Many theories of spoken word recognition assume that lexical items are stored in memory as abstract representations. However, recent research (e.g., Goldinger, 1996) has suggested that representations of spoken words in memory are veridical exemplars that encode specific information, such as characteristics of the talker’s voice. If representations are exemplar based, effects of stimulus variation such as that arising from changes in the identity of the talker may have an effect on identification of and memory for spoken words. This prediction was examined for an implicit and explicit task (lexical decision and recognition, respectively). Comparable amounts of repetition priming in lexical decision were found for repeated words, regardless of whether the repetitions were in the same or in different voices. However, reaction times in the recognition task were faster if the repetition was in the same voice. These results suggest a role for both abstract and specific representations in models of spoken word recognition.     

Effects of talker variability on recall of spoken word lists

Three experiments were conducted to investigate recall of lists of words containing items spoken by either a single talker or by different talkers. In each experiment, recall of early list items was better for lists spoken by a single talker than for lists of the same words spoken by different talkers. The use of a memory preload procedure demonstrated that recall of visually presented preload digits was superior when the words in a subsequent list were spoken by a single talker than by different talkers. In addition, a retroactive interference task demonstrated that the effects of talker variability on the recall of early list items were not due to use of talker-specific acoustic cues in working memory at the time of recall. Taken together, the results suggest that word lists produced by different talkers require more processing resources in working memory than do lists produced by a single talker. The findings are discussed in terms of the role that active rehearsal plays in the transfer of spoken items into long-term memory and the factors that may affect the efficiency of rehearsal.     

Semantic priming,not repetition priming,is to blame for false hearing

Contextual and sensory information are combined in speech perception. Conflict between the two can lead to false hearing, defined as a high-confidence misidentification of a spoken word. Rogers, Jacoby, and Sommers (Psychology and Aging, 27(1), 33–45, 2012) found that older adults are more susceptible to false hearing than are young adults, using a combination of semantic priming and repetition priming to create context. In this study, the type of context (repetition vs. sematic priming) responsible for false hearing was examined. Older and young adult participants read and listened to a list of paired associates (e.g., ROW–BOAT) and were told to remember the pairs for a later memory test. Following the memory test, participants identified words masked in noise that were preceded by a cue word in the clear. Targets were semantically associated to the cue (e.g., ROW–BOAT), unrelated to the cue (e.g., JAW–PASS), or phonologically related to a semantic associate of the cue (e.g., ROW–GOAT). How often each cue word and its paired associate were presented prior to the memory test was manipulated (0, 3, or 5 times) to test effects of repetition priming. Results showed repetitions had no effect on rates of context-based listening or false hearing. However, repetition did significantly increase sensory information as a basis for metacognitive judgments in young and older adults. This pattern suggests that semantic priming dominates as the basis for false hearing and highlights context and sensory information operating as qualitatively different bases for listening and metacognition.     

Effects of lexical competition on immediate memory span for spoken words

Current theories and models of the structural organization of verbal short-term memory are primarily based on evidence obtained from manipulations of features inherent in the short-term traces of the presented stimuli, such as phonological similarity. In the present study, we investigated whether properties of the stimuli that are not inherent in the short-term traces of spoken words would affect performance in an immediate memory span task. We studied the lexical neighbourhood properties of the stimulus items, which are based on the structure and organization of words in the mental lexicon. The experiments manipulated lexical competition by varying the phonological neighbourhood structure (i.e., neighbourhood density and neighbourhood frequency) of the words on a test list while controlling for word frequency and intra-set phonological similarity (family size). Immediate memory span for spoken words was measured under repeated and nonrepeated sampling procedures. The results demonstrated that lexical competition only emerged when a nonrepeated sampling procedure was used and the participants had to access new words from their lexicons. These findings were not dependent on individual differences in short-term memory capacity. Additional results showed that the lexical competition effects did not interact with proactive interference. Analyses of error patterns indicated that item-type errors, but not positional errors, were influenced by the lexical attributes of the stimulus items. These results complement and extend previous findings that have argued for separate contributions of long-term knowledge and short-term memory rehearsal processes in immediate verbal serial recall tasks.     

Rehearsal dynamics in elementary school children

Several studies on free recall suggest that processes responsible for recall are analogous to processes responsible for rehearsal. In children, the relationship between cumulative rehearsal and recall performance has been proven to be critical; however, the locus of the effect of rehearsal is not yet fully understood. To unfold the mechanisms that come into play in an overt rehearsal free recall task, we assessed rehearsal and recall sequences in children between 8 and 10 years of age. These sequences give information about the context in which items are repeated and rearranged throughout the list and subsequently recalled. Rehearsal sequences consisted mainly of items from neighboring list positions in their original temporal order. The same characteristics were true for recall sequences. Qualitatively, order effects during study and recall did not differ over age groups. However, in older children who were using cumulative rehearsal more intensively, successive rehearsal and recall of items in their original order was more pronounced. Therefore, we suggest that a main feature of item rehearsal with regard to facilitating recall is the strengthening of interitem associations based on the temporal order within a list and that this characteristic develops with age.     

Spacing and lag effects in free recall of pure lists

Repeating list items leads to better recall when the repetitions are separated by several unique items than when they are presented successively; thespacing effect refers to improved recall for spaced versus successive repetition (lag > 0 vs. lag = 0); thelag effect refers to improved recall for long lags versus short lags. Previous demonstrations of the lag effect have utilized lists containing a mixture of items with varying degrees of spacing. Because differential rehearsal of items in mixed lists may exaggerate any effects of spacing, it is important to demonstrate these effects in pure lists. As in Toppino and Schneider (1999), we found an overall advantage for recall of spaced lists. We further report the first demonstration of a lag effect in pure lists, with significantly better recall for lists with widely spaced repetitions than for those with moderately spaced repetitions.     

Developmental differences in rehearsal and free recall

The purpose of this experiment was to analyze developmental differences in rehearsal strategies which may mediate the commonly found age effect on free recall. As expected, significant age differences in recall were found; analysis of rehearsal strategies showed that fifth and eighth graders tended to repeat stimulus words immediately after presentation, and not enter items into subsequent rehearsal sets. Adults, in contrast, tended to reenter items for additional rehearsal, and had larger rehearsal buffers. Immediate repetition may have served as additional massed presentation trials, which are less consequential for learning than later reentry of items (spaced trials). It was inferred that children engaged primarily in maintenance rehearsal, and adults in both maintenance and elaborative rehearsal.     

Memory, acquisition, and category clustering in learning-disabled children.

In Experiment 1, single trial, immediate-free recall of learning disabled and nondisabled children was compared. The primacy effect in learning-disabled children was lower, suggesting that rehearsal or other types of elaborative encoding may be deficient in these children. In Experiment 2, acquisition of randomly presented categorical lists in a multitrial-free recall task was compared in learning disabled and nondisabled children. One-half of each group was required to learn the same number of words (34 per list), whereas list length for the other half exceeded the primacy effect of each child in immediate-free recall to the same degree. When the same number of items was learned, acquisition was slower in learning disabled than nondisabled children. When the number of items varied according to the primacy effect of each child, acquisition of both groups was similar. Clustering was lower in learning disabled than nondisabled children. In Experiment 3, multitrial-free recall acquisition of categorical lists was examined in a subject-paced task. When the number of words learned exceeded the primacy effect of each child to the same degree, trials to criterion were similar in both groups but, when the children learned the same number of items, learning-disabled children required more trials to criterion. Presentation rates were faster in learning-disabled children. Presentation rates were negatively correlated with trials to criterion and positively correlated with clustering and primacy in immediate-free recall, suggesting that study time may be taken up by clustering, rehearsal, and/or other encoding strategies. Deficient elaborative encoding may be responsible for the slower acquisition of learning-disabled children.     

Effects of stimulus variability on perception and representation of spoken words in memory

A series of experiments was conducted to investigate the effects of stimulus variability on the memory representations for spoken words. A serial recall task was used to study the effects of changes in speaking rate, talker variability, and overall amplitude on the initial encoding, rehearsal, and recall of lists of spoken words. Interstimulus interval (ISI) was manipulated to determine the time course and nature of processing. The results indicated that at short ISIs, variations in both talker and speaking rate imposed a processing cost that was reflected in poorer serial recall for the primacy portion of word lists. At longer ISIs, however, variation in talker characteristics resulted in improved recall in initial list positions, whereas variation in speaking rate had no effect on recall performance. Amplitude variability had no effect on serial recall across all ISIs. Taken together, these results suggest that encoding of stimulus dimensions such as talker characteristics, speaking rate, and overall amplitude may be the result of distinct perceptual operations. The effects of these sources of stimulus variability in speech are discussed with regard to perceptual saliency, processing demands, and memory representation for spoken words.     

Developmental recall lag in learning-disabled children: Perceptual deficit or verbal mediation deficiency?

To investigate the development of mediational deficiencies in verbal and non-verbal visual short-term memory of learning disabled children, the recall task of Atkinson, Hansen, and Bernback was administered to learning disabled children in two experimental conditions. In Experiment 1 no significant diferences on nonverbal short-term memory recall between normal and learning-disabled children were found. Similar recall responses (e.g., middle response bias, primacy effects, and recency effects) were found for both groups. Non-verbal recall was comparable for disabled and normal children as suggested by stimulus content and association scores/. Experiment 2 found that while the effects of overt rehearsal on pretrained labels on learning disabled children's recall was negligible, labels provided superior recall for normal children. Results suggested that learning disabled children suffer from a verbal mediational deficiency consistent with Flavell's (1970) mediation deficiency hypothesis.The research herein was supported by a faculty research grant at the University of Northern Colorado. Appreciation is due to the Albuquerque (New Mexico) Public School System and the Richland 1 School District, Columbia, South Carolina.     

Change detection: evidence for information accumulation in flicker paradigms

Change detection in rapidly alternating pictures separated by a blank frame has been shown to be very difficult (e.g., [Rensink, R. A., O'Regan, J. K., & Clark, J. J. (1997). To see or not to see: The need for attention to perceive changes in scenes. Psychological Science, 8, 368-373]). The three experiments reported here focus on the mechanism behind detection. More specifically, we explored whether information about the stimulus material accumulates in visual memory and thereby improves change detection. For that purpose the first experiment varied the number of repetitions of the original and modified stimulus version. Results showed that detection improved with more repetitions. The second experiment demonstrated that repetition performance improved more when both the original and the modified picture were repeated. Finally, the third experiment strengthened these findings by showing poorer detection performance when the repetition sequence was randomized. Together, our findings suggest accumulation of information in memory over picture presentations and moreover improved performance when both picture types were repeated. These results underline the importance of developing representations for both picture versions in change detection.     

Individual differences in phonological learning and verbal STM span

A relationship between phonological short-term memory tasks (e.g., nonword repetition, digit span) and vocabulary learning in both experimental and real-life conditions has been reported in numerous studies. A mechanism that would explain this correlation is, however, not known. The present study explores the possibility that it is the quality of phonological representations that affects both short-term recall and long-term learning of novel wordlike items. In Experiment 1, groups with relatively good and poor span for pseudowords were established. The good group was found to perform better at explicit memory tasks tapping the incidental learning of a limited stimulus pool used in an auditory immediate serial pseudoword recall task. In Experiment 2, the results of Experiment 1 were replicated when experience of correct recall was controlled. In Experiment 3, the immediate recall performance of the good group was found to benefit more than that of the poor group from syllable repetition within stimulus pools. It is concluded that the efficiency of a process that creates phonological representations is related both to short-term capacity for verbal items, and to long-term phonological learning of the structure of novel phonological items.     

Differential effects of repetition on pre- and postcategorical memory traces

The effect of list repetition on immediate recall for aurally presented nine-letter lists was studied under two conditions. In the first, a redundant stimulus item was presented as the tenth item in each list, while the suffix was not included in a control condition. As in previous research (Crowder & Morton, 1969), the stimulus suffix selectively interfered with recall at the terminal presentation serial positions, indicating the presence of precategorical acoustic storage. Repetition had a nonselective effect on performance. This result and an analysis of acoustic errors support the inference that qualitative differences in the memory code may lead to differences in other functional properties of the memory trace, such as responsiveness to repetition.     

Repetition deficits, list context, and word-class interactions in the RSVP of words in sentences.

We report a failure to find a repetition deficit in recall following the rapid serial visual presentation (RSVP) of words within sentences, using adjectives rather than nouns as the critical items. In a series of experiments that ruled out participant and procedural differences as the source of the failure, both word class and list context were found to moderate the repetition deficit, but grammatical necessity did not. The presence in the list of sentences in which the repeated adjectives were separated by more than three words (i.e., more than 400 ms in RSVP) not only eliminated the repetition deficit for the recall of those sentences but also for the recall of sentences in which the repeated adjectives were separated by three or fewer words (i.e., less than 400 ms in RSVP). However, although substantially reduced, a repetition deficit with noun-based materials was still found in this list context. Matching the adjective-based sentences with the noun-based sentences in sentence length and position of the critical items revealed that the moderating effect of word-class on the repetition deficit was mediated by the biases in sentence structure that using different word classes tend to induce.     

A phonetic approach to consonant repetition in early words

The goal of this study was to evaluate movement-based principles for understanding early speech output patterns. Consonant repetition patterns within children's actual productions of word forms were analyzed using spontaneous speech data from 10 typically developing American-English learning children between 12 and 36 months of age. Place of articulation, word level patterns, and developmental trends in CVC and CVCV repeated word forms were evaluated. Labial and coronal place repetitions dominated. Regressive repetition (e.g., [gag] for “dog”) occurred frequently in CVC but not in CVCV word forms. Consonant repetition decreased over time. However, the children produced sound types available reported as being within young children's production system capabilities in consonant repetitions in all time periods. Findings suggest that a movement-based approach can provide a framework for comprehensively characterizing consonant place repetition patterns in early speech development.     

List-strength effect: I. Data and discussion

Extra items added to a list cause memory for the other items to decrease (the list-length effect). In one of the present studies we show that strengthening (or weakening) some items on a list harms (helps) free recall of the remaining list items. This is termed the list-strength effect. However, in seven recognition studies the list-strength effect was either absent or negative. This held whether strengthening was accomplished by extra study time or extra repetitions. The seven studies used various means to control rehearsal strategies, thereby providing evidence against the possibility that the findings were due to redistribution of rehearsal or effort from stronger to weaker items within a list. Current models appear unable to predict these results. We suggest that different retrieval operations underlie recall and recognition, as in the SAM model of Gillund and Shiffrin (1984), which can be made to fit the results with certain relatively minor modifications.     

Verbal memory abilities of children with brain tumors.

Several critical neuroanatomical structures and pathways for memory performance are located in the third ventricle region. This led us to predict that verbal memory abilities would be more impaired in children treated for third ventricle tumors compared to those treated for cerebellar tumors. Archival data was obtained from 24 pediatric patients with third ventricle region tumors and 18 pediatric patients with cerebellar tumors. Neuroradiological verifications of tumor involvement and hydrocephalus severity (i.e., Evans Index) on preoperative scans and MRIs proximal to the time of the neuropsychological evaluation were conducted. The potential confounds of hydrocephalus severity, seizure medication, age, radiation treatment, and chemotherapy were addressed. Verbal IQ was comparable between tumor groups and in the Average range. The third ventricle region group performed significantly worse on list learning and delayed list recall compared to the cerebellar group. Their mean performance was in the clinically impaired range on both trials. The third ventricle region tumor group performed better than the cerebellar tumor group on Digit Span, a basic repetition, attention span task. These findings support the hypothesis that pediatric patients with third ventricle region brain tumors are more likely to be impaired on verbal recall tasks compared to pediatric patients with cerebellar brain tumors. In contrast, patients who were treated for cerebellar tumors were more impaired on the basic repetition, attention span task compared to patients who were treated for third ventricle tumors. Future studies should examine the specific neuroanatomical structures and pathways that are damaged and may influence differential cognitive impairments in children.