Implicit serial learning: Questions inspired by Hebb (1961)

Implicit serial learning occurs when indirect measures such as transfer reveal learning of a repeating sequence even when subjects are not informed ofthe repeating sequence, are not asked to learn it, and do not become of aware of it. This phenomenon is reminiscent of an experiment by Hebb(1961), who studied the repetition of sequences in a serial recall task. Two experiments investigated the relation between implicit serial learning and ideas about learning forwarded by Hebb and others who used his method. The experiments showed that implicit serial learning occurs even when the repeating sequence is intermixed with randomly generated sequences instead of being repeated continuously, that the organization of the sequence into regularly or irregularly grouped subsequences determines the extent of learning, and that the repetition effect observed does not depend on subjects' ability to recognize the repetition.     

Hebb repetition effects for non-verbal visual sequences: determinants of sequence acquisition

We report four experiments premised upon the work of Horton et al. [(2008). Hebb repetition effects in visual memory: The roles of verbal rehearsal and distinctiveness. Quarterly Journal of Experimental Psychology, 61(12), 1769–1777] and Page et al. [(2013). Repetition-spacing and item-overlap effects in the Hebb repetition task. Journal of Memory and Language, 69(4), 506–526], and explore conditions under which the visual Hebb repetition effect is observed. Experiment 1 showed that repetition learning is evident when the items comprising the non-repeated (filler) sequences and the repeated (Hebb) sequences are different (no-overlap). However, learning is abolished when the filler and Hebb sequences comprise the same items (full-overlap). Learning of the repeated sequence persisted when repetition spacing was increased to six trials (Experiment 2), consistent with that shown for verbal stimuli (Page et al., 2013). In Experiment 3, it was shown that learning for the repeated sequence is accentuated when the output motor response at test is also repeated for the Hebb sequence, but only under conditions of no-overlap. In Experiment 4, repetition spacing was re-examined with a repeated motor output response (a closer methodological analogue to Page et al., 2013). Under these conditions, the gradient of Hebb repetition learning for six trial repetition intervals was markedly similar to that for three trial intervals. These findings further support the universality of the Hebb repetition effect across memory and are discussed in terms of evidence for amodality within-sequence memory.     

Contextual modulation of prime response retrieval processes: Evidence from auditory negative priming

Contextual similarity between learning and test phase has been shown to be beneficial for memory retrieval. Negative priming is known to be caused by multiple processes; one of which is episodic retrieval. Therefore, the contextual similarity of prime and probe presentations should influence the size of the negative priming effect. This has been shown for the visual modality. In Experiment 1, an auditory four-alternative forced choice reaction time task was used to test the influence of prime-probe contextual similarity on negative priming and the processes underlying the modulation by context. The negative priming effect was larger when the auditory context was repeated than when it was changed from prime to probe. The modulation by context was exclusively caused by an increase in prime response retrieval errors in ignored repetition trials with context repetition, whereas repeating only the context but not the prime distractor did not lead to an increase in prime response retrieval. This exact pattern of results was replicated in Experiment 2. The findings suggest that contextual information is integrated with prime distractor and response information. Retrieval of the previous episode, including prime distractor, prime response, and context (event file), can be triggered when the former prime distractor is repeated, whereas a context cue alone does not retrieve the event file. This suggests an event file structure that is more complicated than its usually assumed binary structure.     

The role of color in visual search in real-world scenes: evidence from contextual cuing

Because the importance of color in visual tasks such as object identification and scene memory has been debated, we sought to determine whether color is used to guide visual search in contextual cuing with real-world scenes. In Experiment 1, participants searched for targets in repeated scenes that were shown in one of three conditions: natural colors, unnatural colors that remained consistent across repetitions, and unnatural colors that changed on every repetition. We found that the pattern of learning was the same in all three conditions. In Experiment 2, we did a transfer test in which the repeating scenes were shown in consistent colors that suddenly changed on the last block of the experiment. The color change had no effect on search times, relative to a condition in which the colors did not change. In Experiments 3 and 4, we replicated Experiments 1 and 2, using scenes from a color-diagnostic category of scenes, and obtained similar results. We conclude that color is not used to guide visual search in real-world contextual cuing, a finding that constrains the role of color in scene identification and recognition processes.     

Stimulus repetition effects on texture-based visual search by pigeons

Four experiments investigated the effects of within-session stimulus repetition on texture discrimination. Six pigeons (Columba livia) searched for a contrasting target region (color or shape) randomly embedded within a larger distractor region for food reinforcement. Experiment 1 found that repeating features of the distractors, but not those of the target, across trials increased the accuracy of target localization relative to baseline. Experiment 2 found that subsequently switching the identity of a repeated distractor feature to the target decreased accuracy. Experiment 3 found that the effects of repeating a distractor feature influenced search performance for at least 60 trials after this learning. Experiment 4 found that differential stimulus-outcome relations can produce control by repeated target features. The results are discussed in terms of the factors and strategies involved in the control of avian visual search behavior.     

汉语颠倒词加工中重复知盲发生的水平

以汉语中的颠倒词为材料, 探讨汉语重复知盲的发生水平。采用RSVP方式呈现包含颠倒词对(C1和C2)的句子列表或词语列表, 让被试对列表中的词进行全部报告或报告是否存在重复词, 记录报告C2的正确率。三个实验采用3 (词语的重复性: 颠倒重复、完全重复、不重复) × 2 (颠倒词对的意义相似性: 意义不同、意义相似)两因素被试内设计, 结果在全部报告和报告是否存在重复词的实验中都出现重复性和意义相似性的交互效应, 但不同实验任务, 数据模式不同。该结果表明, 在RSVP任务中, 汉语颠倒词加工存在RB效应, 该效应产生的水平受制于不同的实验任务, 在部分报告任务中, 颠倒词的RB效应发生在知觉水平, 在全部报告任务中, 颠倒词的RB效应发生在语义水平。     

Two effects of repetition: Support for a dual-process model of know judgments and exclusion errors

In three experiments, aremember/know recognition test (Experiments 1–2) and an exclusion test (Experiments 2–3) were used to examine effects of repeated study presentations. An effect of study repetition was obtained for remember but not know judgments, similar to results reported by Gardiner, Kaminska, Dixon, and Java (1996). Experiment 2 demonstrated the similarity between know responses and exclusion errors; neither was affected by repeated study presentations. In Experiment 3, a response deadline procedure was used to show that exclusion errors are the product of two opposing processes—recollection and familiarity—both of which are influenced by repetition. The interpretation of exclusion errors and know responses is shown to require a dual-process model that includes an assumption about the relationship between processes.     

Segmentation and speech perception in relation to reading skill: a developmental analysis

The present paper examines the processing of speech by dyslexic readers and compares their performance with that of age-matched (CA) and reading-ability-matched (RA) controls. In Experiment 1, subjects repeated single-syllable stimuli (words and nonwords) presented either in a favorable signal-to-noise ratio or with noise masking. Noise affected all subjects to the same extent. Dyslexic children performed as well as controls when repeating high-frequency words, but they had difficulty relative to CA-controls with low-frequency words and relative to both CA- and RA-controls when repeating nonwords. In Experiments 2 and 3, subjects made auditory lexical decisions about the stimuli presented in Experiment 1. Dyslexics performed less well than CA-controls, gaining similar scores to RA-controls. Thus, their difficulty in repeating low-frequency words could be reinterpreted as a difficulty with nonword repetition. Taken together, these results suggest that dyslexics have difficulty with the nonlexical procedures (including phoneme segmentation) involved in verbal repetition. One consequence is that they take longer to consolidate "new" words; verbal memory and reading processes are also compromised.     

Repetition benefit in mental rotation is independent of stimulus repetition

In this study, we investigated whether there is a repetition benefit in mental rotation that is independent of stimulus repetition (i.e., due to increased efficiency in postencoding processing). Three experiments were conducted, in which different conditions of stimulus repetition (different letters on consecutive trials in Experiment 1, letters of different orientations on consecutive trials in Experiment 2, and priming of rotation direction in Experiment 3) were used, and the extent of repetition of rotation direction between two consecutive trials was manipulated. The results of all three experiments showed clear evidence of a repetition benefit without repeating the stimulus, suggesting that this effect is independent of stimulus repetition and lending support to the notion of increased efficiency in mental rotation as a result of repeated rotation direction per se.     

Repetition priming of face recognition

Three experiments investigating the priming of the recognition of familiar faces are reported. In Experiment 1, recognizing the face of a celebrity in an “Is this face familiar?” task was primed by exposure several minutes earlier to a different photograph of the same person, but not by exposure to the person's written name (a partial replication of Bruce and Valentine, 1985). In Experiment 2, recognizing the face of a personal acquaintance was again primed by recognizing a different photograph of their face, but not by recognizing the acquaintance from that person's body shape, clothes etc. Experiment 3 showed that maximum repetition priming is obtained from prior exposure to an identical photograph of a famous face, less from a similar photograph, and least (but still significant) from a dissimilar photograph.

We argue that repetition priming is a function of the degree of physical similarity between two stimuli and that lack of priming between different stimulus types (e.g., written names and faces, or bodies and faces) may be attributable to lack of physical similarity between prime and test stimuli. Repetition priming effects may be best explained by some form of “instance-based” model such as that proposed by McClelland and Rumelhart (1985).     

Inhibition of return for target discriminations: the effect of repeating discriminated and irrelevant stimulus dimensions

Inhibition of return (IOR) refers to slowed reaction times when a target repeats in the same location as a preceding stimulus. In four experiments, the participants were presented with two successive stimuli, S1 and S2. In Experiments 1 and 2, the participants made a speeded discrimination of the identity or orientation of both S1 and S2 (Experiment 1) or of S2 only (Experiment 2). An IOR effect occurred for the repetition of stimulus location, but a facilitatory effect occurred if the stimulus remained unchanged or if an overt response was repeated. In Experiments 3 and 4, the participants localized S1 and S2 (Experiment 3) or S2 only (Experiment 4) to the left or right of center. In this case, repeating the same stimulus had no effect: IOR occurred any time stimulus location repeated. These results demonstrate that the expression of IOR is modulated by the repetition of a target object, but only when the task requires the discrimination of that object; when no discrimination is required, IOR is unaffected.     

The influence of acoustic and semantic similarity on long-term memory for word sequences

It has been shown that short-term memory (STM) for word sequences is grossly impaired when acoustically similar words are used, but is relatively unaffected by semantic similarity. This study tests the hypothesis that long-term memory (LTM) will be similarly affected. In Experiment I subjects attempted to learn one of four lists of 10 words. The lists comprised either acoustically or semantically similar words (A and C) or control words of equal frequency (B and D). Lists were learned for four trials, after which subjects spent 20 min. on a task involving immediate memory for digits. They were then asked to recall the word list. The acoustically similar list was learned relatively slowly, but unlike the other three lists showed no forgetting. Experiment II showed that this latter paradox can be explained by assuming the learning score to depend on both LTM and STM, whereas the subsequent retest depends only on LTM. Experiment III repeats Experiment I but attempts to minimize the effects of STM during learning by interposing a task to prevent rehearsal between the presentation and testing of the word sequences. Unlike STM, LTM proved to be impaired by semantic similarity but not by acoustic similarity. It is concluded that STM and LTM employ different coding systems.     

The role of overt language production in the Hebb repetition effect

The Hebb repetition effect (Hebb, 1961) occurs when recall performance improves for a list that is repeated during a serial-recall task. This effect is considered a good experimental analogue to language learning. Our objective was to evaluate the role of overt language production in language learning by manipulating recall direction during a Hebb repetition paradigm. In each trial, seven nonsense syllables were presented auditorily. Participants had to orally recall the items either in the presentation order or in reverse order. One sequence was repeated every third trial. In Experiment 1, we compared learning from a group that had recalled the items in their presentation order to learning from a group that had recalled the items in the reverse order. The two groups yielded similar learning rates. In Experiment 2, recall direction was varied between trials. The learning rate was not affected when recall direction varied between trials, suggesting a limited role of overt language production in language learning.     

Aging and auditory temporal sequencing: ordering the elements of repeating tone patterns

In a series of experiments, we examined age-related differences in adults' ability to order sequences of tones presented at various speeds and in contexts designed to promote or to impede stream segregation. In Experiment 1, 32 listeners (16 young, 16 old) were required to identify two repeating sequences that consisted of four tones (two from a high and two from a low frequency range) in different order. In Experiment 2, 32 listeners were required to judge whether the two recycled patterns from Experiment 1 were the same or different. In Experiment 3, four young and four old listeners were tested on the tasks of Experiment 2 over an extended period. In Experiment 4, 16 young and 16 old listeners were tested with sequences that were not recycled and were composed of tones drawn from a narrow frequency range. Elderly adults were less able than young adults to distinguish between tone sequences with contrasting order, regardless of the speed of presentation, the nature of the task (identification vs. same/different), the amount of practice, the frequency separation of the tones, or the presence or absence of recycling. These findings provide evidence of a temporal sequencing impairment in elderly listeners but reveal no indication of age differences in streaming processes.     

Selective scanpath repetition during memory-guided visual search

Visual search efficiency improves with repetition of a search display, yet the mechanisms behind these processing gains remain unclear. According to Scanpath Theory, memory retrieval is mediated by repetition of the pattern of eye movements or “scanpath” elicited during stimulus encoding. Using this framework, we tested the prediction that scanpath recapitulation reflects relational memory guidance during repeated search events. Younger and older subjects were instructed to find changing targets within flickering naturalistic scenes. Search efficiency (search time, number of fixations, fixation duration) and scanpath similarity (repetition) were compared across age groups for novel (V1) and repeated (V2) search events. Younger adults outperformed older adults on all efficiency measures at both V1 and V2, while the search time benefit for repeated viewing (V1–V2) did not differ by age. Fixation-binned scanpath similarity analyses revealed repetition of initial and final (but not middle) V1 fixations at V2, with older adults repeating more initial V1 fixations than young adults. In young adults only, early scanpath similarity correlated negatively with search time at test, indicating increased efficiency, whereas the similarity of V2 fixations to middle V1 fixations predicted poor search performance. We conclude that scanpath compression mediates increased search efficiency by selectively recapitulating encoding fixations that provide goal-relevant input. Extending Scanpath Theory, results suggest that scanpath repetition varies as a function of time and memory integrity.     

Correlational cuing as a function of target complexity and target-flanker similarity

It is generally assumed that the correlational cuing effect (CE) between targets and correlated flankers is due to learning association between the flankers and their correlated responses. The present study challenges this view. Experiment 1 shows that the CE for targets composed of color is eliminated as soon as the correlation is removed. Experiment 2 shows that the CE during training is not due to association of the flankers with responses. Experiment 3 shows that at least some of the CE during training with the correlation is due to repetition priming of the display. Experiment 4 replicates the results of Experiment 1 for orientation targets. In Experiments 5-7, more typical tasks with letter targets are examined, and it is demonstrated that preexperimental similarity between targets and correlated flankers is crucial. The CE for correlated but dissimilar target-flanker pairs, similar to that for color and orientation targets, is confined to on-line processes that occur during training. The CE is transferred, however, for correlated and similar target-flanker pairs. We propose that, at least for the simple stimulus to response mapping used in our study, the CE is not due to learning at all. Instead it is due to (1) on-line processes, such as repetition priming, that occur during training with the correlation and (2) a regular flanker effect (see, e.g., B. A. Eriksen & C. W. Eriksen, 1974) that occurs for similar target-flanker pairs.     

Depth of phonological recoding in short-term memory

In testing the hypothesis that surface phonetic form is included in short-term memory (STM) representation, the tone sandhi phenomenon in Mandarin Chinese was exploited, and, as a prerequisite, the hypothesis that tonal similarity affects STM of verbal material in a tone language was also tested. In Experiment 1, subjects recalled visually presented sequences of seven monosyllabic Chinese morphemes having either the same tone or different tones. More errors were made on the monotonal sequences than on the multitonal sequences, confirming the effect of tonal similarity on STM. In Experiment 2, subjects recalled visually presented sequences of disyllabic nonsense words. The sequences were designed in such a way that half of them were subject to the tone sandhi rule in Mandarin Chinese, whereas the other half were not. The consequence of applying the tone sandhi rule, as designed, was to make all the first characters in the sequences identical in pronunciation, thus creating potential phonological confusion. More errors, indeed, occurred on the sequences subject to the tone sandhi rule than on those not subject to it, indicating the existence of a surface phonetic representation in STM. The findings in this study provide further insight into the phonological mechanism of STM. Different accounts for this mechanism are also discussed in the light of the new findings.     

Memory for sequences of tone bursts in the rat: Reliance on temporal cues and evidence for an instructional ambiguity explanation of the choose-few effect

Two groups of rats were trained in a symbolic delayed matching-to-sample task with a 0-s delay to discriminate sample stimuli that consisted of sequences of tone bursts. For one group, sequences varied in number with total sequence duration controlled. For the other group, total sequence duration, sum of the tone durations, and sum of the gap durations were all controlled. The former group of rats acquired the discrimination, but the latter group of rats were not able to learn the discrimination with the additional temporal cues controlled. Retention functions for the group that acquired the discrimination exhibited a choose-many bias at the 1-s delay and a choose-few bias at the 8-s delay regardless of the similarity in the intertrial interval and delay interval illumination condition. The asymmetrical retention functions appeared to be due to instructional ambiguity which resulted from the similarity of the delay interval to temporal features of the tone burst sequence, such as the gap between tone bursts and the total duration of tone. In Experiment 2, diagnostic tests provided evidence that rats discriminated the sequences of tone bursts by timing and summing the duration of individual tone bursts rather than using an event switch to count tones. Like pigeons, rats use multiple temporal features rather than number to discriminate sequences of successive events.     

The Hebb repetition effect as a laboratory analogue of novel word learning

The present study tests the hypothesis that a common ordering mechanism underlies both short-term serial recall of verbal materials and the acquisition of novel long-term lexical representations, using the Hebb repetition effect. In the first experiment, participants recalled visually presented nonsense syllables following a typical Hebb effect learning protocol. Replicating the Hebb repetition effect, we observed improved recall for repeated sequences of syllables. In the second experiment, the same participants performed an auditory lexical decision task, which included nonwords that were constructed from the syllables used in the first experiment. We observed inhibited rejection of nonwords that were composed of the repeated Hebb sequences, compared to nonwords that were built from nonrepeated filler sequences. This suggests that a long-term phonological lexical representation developed during Hebb learning. Accordingly, the relation between immediate serial recall and word learning is made explicit by arguing that the Hebb repetition effect is a laboratory analogue of naturalistic vocabulary acquisition.     

The Hebb repetition effect as a laboratory analogue of novel word learning

The present study tests the hypothesis that a common ordering mechanism underlies both short-term serial recall of verbal materials and the acquisition of novel long-term lexical representations, using the Hebb repetition effect. In the first experiment, participants recalled visually presented nonsense syllables following a typical Hebb effect learning protocol. Replicating the Hebb repetition effect, we observed improved recall for repeated sequences of syllables. In the second experiment, the same participants performed an auditory lexical decision task, which included nonwords that were constructed from the syllables used in the first experiment. We observed inhibited rejection of nonwords that were composed of the repeated Hebb sequences, compared to nonwords that were built from nonrepeated filler sequences. This suggests that a long-term phonological lexical representation developed during Hebb learning. Accordingly, the relation between immediate serial recall and word learning is made explicit by arguing that the Hebb repetition effect is a laboratory analogue of naturalistic vocabulary acquisition.