Task-switching cost and repetition priming: Two overlooked confounds in the fixed-set procedure of the Sternberg paradigm and how they affect memory set-size effects

Subjects performed Sternberg-type memory recognition tasks (Sternberg paradigm) in four experiments. Category-instance names were used as learning and testing materials. Sternberg's original experiments demonstrated a linear relation between reaction time (RT) and memory-set size (MSS). A few later studies found no relation, and other studies found a nonlinear relation (logarithmic) between the two variables. These deviations were used as evidence undermining Sternberg's serial scan theory. This study identified two confounding variables in the fixed-set procedure of the paradigm (where multiple probes are presented at test for a learned memory set) that could generate a MSS RT function that was either flat or logarithmic rather than linearly increasing. These two confounding variables were task-switching cost and repetition priming. The former factor worked against smaller memory sets and in favour of larger sets whereas the latter factor worked in the opposite way. Results demonstrated that a null or a logarithmic RT-to-MSS relation could be the artefact of the combined effects of these two variables. The Sternberg paradigm has been used widely in memory research, and a thorough understanding of the subtle methodological pitfalls is crucial. It is suggested that a varied-set procedure (where only one probe is presented at test for a learned memory set) is a more contamination-free procedure for measuring the MSS effects, and that if a fixed-set procedure is used, it is worthwhile examining the RT function of the very first trials across the MSSs, which are presumably relatively free of contamination by the subsequent trials.     

Repetition priming within and between languages in verb generation: Evidence for shared verb concepts

Although translation equivalents for concrete nouns are known to have shared core conceptual representations in bilingual memory (Francis, 1999), the status of translation-equivalent verbs has not been systematically tested. Three repetition-priming experiments using a verb generation task were used to determine whether verbs have shared representations across languages and to identify the processes facilitated in repeated verb generation. In Experiment 1 fluent Spanish–English bilingual speakers exhibited repetition priming both within and between languages, but between-language priming was weaker. In Experiment 2 performance of non-bilingual English and Spanish speakers was equivalent to that of bilingual speakers responding in their dominant language. Experiment 3 used manipulations meant to isolate noun comprehension, verb concept selection, and verb production. The between-language priming in Experiments 1 and 3 indicates that verb concepts are shared across languages and that verb concept selection exhibits facilitation. Experiment 3 showed that the greater within-language priming was due primarily to facilitation of verb production processes.     

Space-based and object-based capacity limitations in visual search

Space-based accounts of visual attention assume that we select a limited spatial region independent of the number of objects it contains. In contrast, object-based accounts suggest that we select objects independent of their location. We investigated the boundary conditions on the selection modes of attention in a series of tachistoscopic visual search tasks, where the nature of capacity limitations on search was examined. Observers had to search for a horizontally oriented target ellipse among differently oriented distractor ellipses. Across four experiments, we orthogonally manipulated target-distractor (TD) similarity and distractor-distractor (DD) similarity. Each experiment consisted of a two-way design: Firstly, with a central cue, we indicated the spatial extent of the relevant search area. Secondly, we varied the number and spatial proximity of items in the display. Performance could be accounted for in terms of capacity limited object-based attention, assuming also that the spatial proximity of items enhances performance when there is high DD-similarity (and grouping). In addition, the cueing effect interacted with spatial proximity when DD-similarity was high, suggesting that grouping was influenced by attention. We propose that any capacity limits on visual search are due to object-based attention, and that the formation of perceptual objects and object groups is also subject to attentional modulation.     

Preferential processing of threatening facial expressions using the repetition blindness paradigm

Background: Neuroanatomical evidence suggests that the human brain has dedicated pathways to rapidly process threatening stimuli. This processing bias for threat was examined using the repetition blindness (RB) paradigm. RB (i.e., failure to report the second instance of an identical stimulus rapidly following the first) has been established for words, objects and faces but not, to date, facial expressions. Methods: 78 (Study 1) and 62 (Study 2) participants identified repeated and different, threatening and non-threatening emotional facial expressions in rapid serial visual presentation (RSVP) streams. Results: In Study 1, repeated facial expressions produced more RB than different expressions. RB was attenuated for threatening expressions. In Study 2, attenuation of RB for threatening expressions was replicated. Additionally, semantically related but non-identical threatening expressions reduced RB relative to non-threatening stimuli. Conclusions: These findings suggest that the threat bias is apparent in the temporal processing of facial expressions, and expands the RB paradigm by demonstrating that identical facial expressions are susceptible to the effect.     

汉字部件水平的重复知盲效应

本研究采用不同部件特点的汉字材料考察在汉字部件水平的重复知盲效应。实验1探究在一组刺激序列中,当两个关键刺激R1和R2的相同部件在不同位置时对重复知盲效应的影响。实验1结果表明,不同条件的重复知盲效应存在显著差异,但其中两个关键字中相同部件的位置相同时与部件位置不同时之间的重复知盲效应无显著差异,这表明部件位置对重复知盲现象无显著影响。实验2探究当关键刺激R1和R2为部件包含关系时的重复知盲效应。实验2结果表明,当一个关键刺激为独体字,且是另一个关键刺激的部件时存在重复知盲效应,其效应的大小会受到具有包含关系的两个关键字（合体字和独体字）在刺激序列中出现顺序的影响,当第二个关键刺激为独体字时的重复知盲效应要显著强于第二个关键刺激为合体字条件。研究结论是不同的汉字部件特点会影响重复之盲效应,这表明重复知盲现象很可能发生在在线的知觉加工过程。     

Can thematic roles leave traces of their places?

An important question in the study of language production is the nature of the semantic information that speakers use to create syntactic structures. A common answer to this question assumes that thematic roles help to mediate the mapping from messages to syntax. However, research using structural priming has suggested that the construction of syntactic frames may be insensitive to variations in thematic roles within messages (Cognition 35 (1990) 1; Psychological Review 99 (1992) 150). Because these studies involved structural alternations whose syntax covaries with the order of thematic roles, it is difficult to assess any independent contribution that role information may make to the positioning of phrases. In this study, we primed the order of the roles without changing the syntactic structure of the sentences produced, and found that the order of the roles was influenced by the priming manipulation. This implies that thematic roles or the features that differentiate them are active within the mapping between messages and sentence structures.     

Mix me a list: Context moderates the truth effect and the mere-exposure effect

When participants are repeatedly presented with an unfamiliar stimulus, this stimulus is rated as more likable (mere-exposure effect) or more valid (truth effect) as compared with a similar non-repeated stimulus. Both effects have been discussed as effects of fluency. Typical research designs on these effects involve a test phase in which ratings of both repeated and non-repeated stimuli are required. Based on research on moderators of fluency effects, we propose that the procedure of assessing the effects with mixed lists of repeated and non-repeated stimuli contributes strongly to the emergence of both effects. Two experiments found that the truth effect and the mere-exposure effect were strongly moderated by whether mixed lists or only repeated items were used at the test phase: whereas strong effects occurred in a context of repeated and non-repeated stimuli, the effects vanished with only repeated stimuli. Methodological and theoretical implications are discussed.     

Stimulus–classification and stimulus–action associations: Effects of repetition learning and durability

It has been shown that acquired stimulus–response bindings result from at least two types of associations from the stimulus to the task (stimulus–task or stimulus–classification; S–C) and from the stimulus to the motor response (stimulus–response or stimulus–action; S–A). These types of associations have been shown to independently affect behaviour. This finding suggests that they are processed in different pathways or different parts of a pathway at the neural level. Here we test a hypothesis that such associations may be differentially affected by repetition learning and that such effects may be detected by measuring their durability against overwriting. We show that both S–C and S–A associations are in fact strengthened when learning is boosted by increasing repetitions of the primes. However, the results further suggest that associations between stimuli and actions have less durable effects on behaviour and that the durability of S–C and S–A associations is independent of repetition learning. This is an important finding for the understanding of the underlying mechanisms of associative learning and particularly raises the question of which processes may affect flexibility of learning.     

Influence of multiple-day temporal distribution of repetitions on memory: A comparison of uniform,expanding, and contracting schedules

Very few studies have examined the influence of schedules of repetitions across multiple days (e.g., Tsai, 1927 Tsai, L.-S. 1927. The relation of retention to the distribution of relearning. Journal of Experimental Psychology, 10: 30–39. [Crossref] , [Google Scholar]). Three temporal schedules of four presentations of pseudoword/word pairs over a 7-day learning period were compared: a uniform (presentations on Days 1, 3, 5, and 7), an expanding (1, 2, 3, 7), and a contracting (1, 5, 6, 7) schedule. Schedule was a within-subjects variable. Experiment 1 was performed on the Internet and showed that cued recall on Day 9 led to higher scores for the stimuli of the expanding schedule. Experiment 2 was performed in the laboratory and showed that the expanding and the uniform schedules led to the highest scores on Day 9. A recognition task performed during the learning phase revealed that stimuli recognized at the time of their repetition were more likely to be retrieved later than the others. Our results are discussed within the framework of the study-phase retrieval and encoding variability theories.     

Book review

Wheeldon, L. (Ed.). (2000). Aspects of language production. Hove, UK: Psychology Press. Pp.419. ISBN 0-86377-882-8. Price £3995 (Hbk). ISBN 0-86377-883-6. Price £1995 (Pbk, published 2002).