The neural correlates of implicit and explicit sequence learning: Interacting networks revealed by the process dissociation procedure

In two H2(15)O PET scan experiments, we investigated the cerebral correlates of explicit and implicit knowledge in a serial reaction time (SRT) task. To do so, we used a novel application of the Process Dissociation Procedure, a behavioral paradigm that makes it possible to separately assess conscious and unconscious contributions to performance during a subsequent sequence generation task. To manipulate the extent to which the repeating sequential pattern was learned explicitly, we varied the pace of the choice reaction time task-a variable that is known to have differential effects on the extent to which sensitivity to sequence structure involves implicit or explicit knowledge. Results showed that activity in the striatum subtends the implicit component of performance during recollection of a learned sequence, whereas the anterior cingulate/mesial prefrontal cortex (ACC/MPFC) supports the explicit component. Most importantly, we found that the ACC/MPFC exerts control on the activity of the striatum during retrieval of the sequence after explicit learning, whereas the activity of these regions is uncoupled when learning had been essentially implicit. These data suggest that implicit learning processes can be successfully controlled by conscious knowledge when learning is essentially explicit. They also supply further evidence for a partial dissociation between the neural substrates supporting conscious and nonconscious components of performance during recollection of a learned sequence.     

The nature of memory processes underlying recognition judgments in the process dissociation procedure

The hypothesis is tested that the memory processes involved in recognition judgments in the process dissociation procedure are the same as those involved in standard source-monitoring tasks. It is shown how source-monitoring response categories can be mapped onto process dissociation response categories. On the basis of this observation, an experiment was conducted in which it was possible to compare, using a multinomial modeling approach, the parameters representing memory processes in the process dissociation procedure with those involved in source monitoring. For the two different encoding conditions realized, the results are compatible with the hypothesis that the same processes are involved in source monitoring and in recognition judgments in the process dissociation procedure. Implications for the interpretation of the model’s parameters are discussed.     

The EffectLiteR Approach for Analyzing Average and Conditional Effects

We present a framework for estimating average and conditional effects of a discrete treatment variable on a continuous outcome variable, conditioning on categorical and continuous covariates. Using the new approach, termed the EffectLiteR approach, researchers can consider conditional treatment effects given values of all covariates in the analysis and various aggregates of these conditional treatment effects such as average effects, effects on the treated, or aggregated conditional effects given values of a subset of covariates. Building on structural equation modeling, key advantages of the new approach are (1) It allows for latent covariates and outcome variables; (2) it permits (higher order) interactions between the treatment variable and categorical and (latent) continuous covariates; and (3) covariates can be treated as stochastic or fixed. The approach is illustrated by an example, and open source software EffectLiteR is provided, which makes a detailed analysis of effects conveniently accessible for applied researchers.     

Adapting to changing memory retrieval demands: Evidence from event-related potentials

This study investigated preparatory processes involved in adapting to changing episodic memory retrieval demands. Event-related potentials (ERPs) were recorded while participants performed a general old/new recognition task and a specific task that also required retrieval of perceptual details. The relevant task remained either constant or changed (predictably or randomly) across trials. Responses were slowed when participants switched from the specific to the general task but not vice versa. Hence, asymmetrical switch costs were observed, suggesting that retrieval preparation is dependent not only on the current retrieval goal but also influenced by recent retrieval attempts. Consistently, over posterior scalp regions ERPs associated with advance preparation were modulated by the preceding task, reflecting increased attentional selection requirements for the general task, and by the foreknowledge about the task sequence. When retrieval demands remained constant, frontal slow-waves elicited by retrieval-cues were more positive going for the specific task, indicating full implementation of a retrieval orientation that allows more efficient retrieval of perceptual details.     

Framing the framing effect: the impact of context cues on solutions to the ‘Asian disease’ problem

Participants were exposed to the ‘Asian disease’ problem (Tversky & Kahneman, 1981). When the problem was subtly framed as a medical decision problem previous findings were replicated: participants avoided the risky option when the problem was framed positively, but preferred the risky option when the problem was framed negatively. This reversal of preferences was eliminated however, when the same problem was subtly introduced as a statistical problem. The results are interpreted as evidence for the impact of context cues on the representation of decision problems. © 1998 John Wiley & Sons, Ltd.     

Generating anagrams from multiple core strings employing user-defined vocabularies and orthographic parameters

Anagrams are used widely in psychological research. However, generating a range of strings with the same letter content is an inherently difficult and time-consuming task for humans, and current computer-based anagram generators do not provide the controls necessary for psychological research. In this article, we present a computational algorithm that overcomes these problems. Specifically, the algorithm processes automatically each word in a user-defined source vocabulary and outputs, for each word, all possible anagrams that exist as words (or as nonwords, if required) as defined by the same source vocabulary. Moreover, we show how the output of the algorithm can be filtered to produce anagrams within specific user-defined orthographic parameters. For example, the anagrams produced can be filtered to produce words that share, with each other or with other words in the source vocabulary, letters in only certain positions. Finally, we provide free access to the complete Windows-based program and source code containing these facilities for anagram generation.     

Electrophysiological correlates of encoding and retrieving emotional events

This study examined the impact of emotional content on encoding and retrieval processes. Event-related potentials were recorded in a source recognition memory task. During encoding, a posterior positivity for positive and negative pictures (250-450 ms) that presumably reflects attentional capturing of emotionally valenced stimuli was found. Additionally, positive events, which were also rated as less arousing than negative events, gave rise to anterior and posterior slow wave activity as compared with neutral and negative events and also showed enhanced recognition memory. It is assumed that positive low-arousing events enter controlled and elaborated encoding processes that are beneficial for recognition memory performance. The high arousal of negative events may interfere with controlled encoding mechanisms and attenuate item recognition and the quality of remembering. Moreover, topographically distinct late posterior negativities were obtained for the retrieval of the context features location and time that support the view that this component reflects processes in service of reconstructing the study episode by binding together contextual details with an item and that varies with the kind of episodic detail to be retrieved.     

Endogenous versus exogenous change: Change detection,self and agency

The goal of this study is to characterize observers’ abilities to discriminate between endogenous (i.e., self-produced) and exogenous changes. To do so, we developed a new experimental paradigm. On each trial, participants were shown a dot pattern on the screen. Next, the pattern disappeared and participants were to reproduce it. Changes were surreptuously introduced in the stimulus, either by presenting participants anew with the dot pattern they had themselves produced on the previous trial (endogenous change) or by presenting participants with a slightly different dot pattern (exogenous changes). We analyzed awareness of the changes and behavioral adaptation to them in a dynamical manner. We observe (1) signal attenuation in the presence of endogenous change, (2) dissociation between self-attribution reports and behavioral effect of agency. We discuss the source of this sensitive attenuation as well as the relation between a minimal or core self and an extended, narrative or autobiographical self.