Sequences learned without awareness can orient attention during the perception of human activity

Human activity contains sequential dependencies that observers may use to structure a task environment (e.g., the ordering of steps when tying shoes or getting into a car). Two experiments investigated how people take advantage of sequential structure to understand activity and respond to behaviorally relevant events. Participants monitored animations of simplified human movement to identify target hand gestures. In the first experiment, participants were able to use predictive sequential dependencies to more quickly identify targets. In addition, performance was best at the point in time that followed the sequence. However, the second experiment revealed that how sequential structure affects detection depends on whether the sequence predicts the timing of target events. In all cases, sequence learning was observed without participants’ awareness of the sequential dependencies. These results suggest that human activity sequences can be learned without awareness and can be used to adaptively guide behavior.     

The influence of response conflict on voluntary task switching: a novel test of the conflict monitoring model

The conflict monitoring model of cognitive control posits that response conflict triggers a top-down enhancement of a task’s representation in working memory. In the present study, we conducted a novel test of the conflict monitoring model using a voluntary task switching paradigm. We predicted that a task’s representation would be enhanced following events associated with high response conflict (i.e., incongruent trials and incorrect responses), leading participants to voluntarily choose to repeat that task more often after these events than after events associated with low response conflict (i.e., congruent trials and correct responses). In two experiments, performance following incongruent trials was consistent with the conflict monitoring model. However, performance following incorrect trials did not fit with the model’s predictions. These findings provide novel support for the conflict monitoring model while revealing new effects of incorrect trials that the model cannot explain.     

Structural selection in implicit learning of artificial grammars

In the contextual cueing paradigm, Endo and Takeda (in Percept Psychophys 66:293–302, 2004) provided evidence that implicit learning involves selection of the aspect of a structure that is most useful to one’s task. The present study attempted to replicate this finding in artificial grammar learning to investigate whether or not implicit learning commonly involves such a selection. Participants in Experiment 1 were presented with an induction task that could be facilitated by several characteristics of the exemplars. For some participants, those characteristics included a perfectly predictive feature. The results suggested that the aspect of the structure that was most useful to the induction task was selected and learned implicitly. Experiment 2 provided evidence that, although salience affected participants’ awareness of the perfectly predictive feature, selection for implicit learning was mainly based on usefulness.     

Olfactory working memory: effects of verbalization on the 2-back task

Working memory for odors, which has received almost no attention in the literature, was investigated in two experiments. We show that performance in a 2-back task with odor stimuli is well above chance. This is true not only for highly familiar odors, as has been shown by Dade, Zatorre, Evans, and Jones-Gotman, NeuroImage, 14, 650–660, (2001), but also for unfamiliar ones that are notoriously difficult to name. We can conclude that information about an olfactory stimulus can be retained in the short term and can continuously be updated for comparison with new olfactory probes along the lines of a functional odor working memory. However, the performance in the working memory task is highly dependent on participants’ verbalization of the odor. In addition, results indicated that odor working memory performance is dependent on the ability to discriminate among the odor stimuli (Experiment 2). The results are discussed in relation to recent ideas of a separate olfactory working memory slave system.     

Context attributes in memory are bound to item information,but not to one another

In four experiments, we compared binding between item and context information with binding between different types of context information. Participants studied line drawings of common objects that appeared in both different colors and different locations. We explored the effects of reinstating one type of information on recognition memory for another type, and we also tested the participants’ ability to discriminate intact from rearranged pairings of two types of information. Results showed that different contextual dimensions (i.e., color and location) were bound to item information (i.e., object information), but not to each other.     

Does survival processing enhance implicit memory?

Recent research has shown that human memory may have evolved to remember information that has been processed for the purpose of survival, more so than information that has been processed for other purposes, such as home-moving. We investigated this survival-processing advantage using both explicit and implicit memory tests. In Experiment 1, participants rated words in one of three scenarios: survival, pleasantness, and moving, followed by a timed stem-cued recall/stem-cued completion task. Items were completed more quickly in the survival scenario, as compared with the other two for the explicit task, but no differences were found across conditions in the implicit task. In Experiment 2, the implicit task was changed to concreteness judgments to encourage more conceptual processing. Again, the survival-processing advantage occurred in the explicit task (speeded item recognition), but not in the implicit task. These results suggest that a survival-processing advantage may benefit participants’ memory performance only during explicit retrieval.     

Evidence for an implicit influence of memory on future thinking

The capacity to think about specific events that one might encounter in the future—episodic future thought— involves the flexible (re)organization of memory. The present study demonstrates that implicit processes play an important role here. In two experiments (N = 180), participants were asked to generate a personal event that they expected to plausibly occur in the following week. The content of the participants’ responses was biased (i.e., primed) by recent thoughts about a specific category of experiences. For instance, participants who had recently been induced to think about social experiences, in the context of an ostensibly unrelated task, were more likely than nonprimed participants to generate similar events occurring in their immediate future. Importantly, the participants were unaware of this unintentional influence of memory. The theoretical and practical implications of these findings for understanding episodic future thought and its relation to memory are discussed.     

Intrinsic orientation and study viewpoint in recognizing spatial structure of a shape

Two experiments dissociated the roles of intrinsic orientation of a shape and participants’ study viewpoint in shape recognition. In Experiment 1, participants learned shapes with a rectangular background that was oriented differently from their viewpoint, and then recognized target shapes, which were created by splitting study shapes along different intrinsic axes, at different views. Results showed that recognition was quicker when the study shapes were split along the axis parallel to the orientation of the rectangular background than when they were split along the axis parallel to participants’ viewpoint. In Experiment 2, participants learned shapes without the rectangular background. The results showed that recognition was quicker when the study shape was split along the axis parallel to participants’ viewpoint. In both experiments, recognition was quicker at the study view than at a novel view. An intrinsic model of object representation and recognition was proposed to explain these findings.     

Chunking in task sequences modulates task inhibition

In a study of the formation of representations of task sequences and its influence on task inhibition, participants first performed tasks in a predictable sequence (e.g., ABACBC) and then performed the tasks in a random sequence. Half of the participants were explicitly instructed about the predictable sequence, whereas the other participants did not receive these instructions. Task-sequence learning was inferred from shorter reaction times (RTs) in predictable relative to random sequences. Persisting inhibition of competing tasks was indicated by increased RTs in n- 2 task repetitions (e.g., ABA) compared with n- 2 nonrepetitions (e.g., CBA). The results show task-sequence learning for both groups. However, task inhibition was reduced in predictable relative to random sequences among instructed-learning participants who formed an explicit representation of the task sequence, whereas sequence learning and task inhibition were independent in the noninstructed group. We hypothesize that the explicit instructions led to chunking of the task sequence, and that n- 2 repetitions served as chunk points (ABA-CBC), so that within-chunk facilitation modulated the inhibition effect.     

Affective guidance in the Iowa gambling task

It has been suggested that affective states can guide higher level cognitive processes and that such affective guidance may be particularly important when real-life decisions are made under uncertainty. We ask whether affect guides decisions in a laboratory task that models real-life decisions under uncertainty. In the Iowa gambling task (IGT), participants search for monetary payoffs in an uncertain environment. Recent evidence against an affective guidance interpretation of the IGT indicates a need to set a standard for what counts as evidence of affective guidance. We present a novel analysis of IGT, and our results show that participants’ galvanic skin response (GSR) reflects an affective process that precedes and guides cognition. Specifically, prior to participants’ knowledge of the optimal strategy, their GSRs are significantly higher when they are about to select from a bad deck, relative to a good deck, and this difference in GSR is correlated with a behavioral preference for the good deck.     

Scene context influences without scene gist: Eye movements guided by spatial associations in visual search

Although the use of semantic information about the world seems ubiquitous in every task we perform, it is not clear whether we rely on a scene’s semantic information to guide attention when searching for something in a specific scene context (e.g., keys in one’s living room). To address this question, we compared contribution of a scene’s semantic information (i.e., scene gist) versus learned spatial associations between objects and context. Using the flash-preview–moving-window paradigm Castelhano and Henderson (Journal of Experimental Psychology: Human Perception and Performance 33:753–763, 2007), participants searched for target objects that were placed in either consistent or inconsistent locations and were semantically consistent or inconsistent with the scene gist. The results showed that learned spatial associations were used to guide search even in inconsistent contexts, providing evidence that scene context can affect search performance without consistent scene gist information. We discuss the results in terms of hierarchical organization of top-down influences of scene context.     

The effects of workload history on dual task performance

The purpose of this study was to examine the effects of workload history (specifically sudden workload shifts) on performance. A sample of 204 undergraduates was randomly assigned to either a sudden decrease or increase in workload condition. Participants simultaneously performed a memory search task (i.e., primary task) and an auditory vigilance task (i.e., distracter task), while percent correct was recorded. Separate Repeated Measures ANOVA’s revealed a significant treatment effect for the Medium to Low (F(l, 110) = 274.6, p < .01) and Low to Medium (F(l,92) = 148.3, p < .01) conditions. Results supported previous research suggesting that either a sudden decrease (Medium to Low) or increase (Low to Medium) in workload could be detrimental to performance (Cox-Fuenzalida, 2000). More importantly, this study extends the detrimental effects of workload history to a dual task environment. The authors express their gratitude to the research team from the Personality and Human Performance Lab at the University of Oklahoma for their invaluable assistance in data planning and collection.     

The effects of workload history on dual task performance

The purpose of this study was to examine the effects of workload history (specifically sudden workload shifts) on performance. A sample of 204 undergraduates was randomly assigned to either a sudden decrease or increase in workload condition. Participants simultaneously performed a memory search task (i.e., primary task) and an auditory vigilance task (i.e., distracter task), while percent correct was recorded. Separate Repeated Measures ANOVA’s revealed a significant treatment effect for the Medium to Low (F(l, 110) = 274.6, p < .01) and Low to Medium (F(l,92) = 148.3, p < .01) conditions. Results supported previous research suggesting that either a sudden decrease (Medium to Low) or increase (Low to Medium) in workload could be detrimental to performance (Cox-Fuenzalida, 2000). More importantly, this study extends the detrimental effects of workload history to a dual task environment. The authors express their gratitude to the research team from the Personality and Human Performance Lab at the University of Oklahoma for their invaluable assistance in data planning and collection.     

A modulatory effect of male voice pitch on long-term memory in women: evidence of adaptation for mate choice?

From a functionalist perspective, human memory should be attuned to information of adaptive value for one’s survival and reproductive fitness. While evidence of sensitivity to survival-related information is growing, specific links between memory and information that could impact upon reproductive fitness have remained elusive. Here, in two experiments, we showed that memory in women is sensitive to male voice pitch, a sexually dimorphic cue important for mate choice because it not only serves as an indicator of genetic quality, but may also signal behavioural traits undesirable in a long-term partner. In Experiment 1, we report that women’s visual object memory is significantly enhanced when an object’s name is spoken during encoding in a masculinised (i.e., lower-pitch) versus feminised (i.e., higher-pitch) male voice, but that no analogous effect occurs when women listen to other women’s voices. Experiment 2 replicated this pattern of results, additionally showing that lowering and raising male voice pitch enhanced and impaired women’s memory, respectively, relative to a baseline (i.e., unmanipulated) voice condition. The modulatory effect of sexual dimorphism cues in the male voice may reveal a mate-choice adaptation within women’s memory, sculpted by evolution in response to the dilemma posed by the double-edged qualities of male masculinity.     

Recruitment of intuitive versus analytic thinking strategies affects the role of working memory in a gambling task

Previous studies found mixed results concerning the role of working memory (WM) in the gambling task (GT). Here, we aimed at reconciling inconsistencies by showing that the standard version of the task can be solved using intuitive strategies operating automatically, while more complex versions require analytic strategies drawing on executive functions. In Study 1, where good performance on the GT could be achieved using intuitive strategies, participants performed well both with and without a concurrent WM load. In Study 2, where analytical strategies were required to solve a more complex version of the GT, participants without WM load performed well, while participants with WM load performed poorly. In Study 3, where the complexity of the GT was further increased, participants in both conditions performed poorly. In addition to the standard performance measure, we used participants’ subjective expected utility, showing that it differs from the standard measure in some important aspects.     

Implicit learning of fifth- and sixth-order sequential probabilities

Serial reaction time (SRT) task studies have established that people can implicitly learn sequential contingencies as complex as fourth-order probabilities. The present study examined people’s ability to learn fifth-order (Experiment 1) and sixth-order (Experiment 2) probabilities. Remarkably, people learned fifth- and sixth-order probabilities. This suggests that the implicit sequence learning mechanism can operate over a range of at least seven sequence elements.     

Explicit Awareness does not Modulate Retrograde Interference Effects in Sequence Learning

Motor sequences are learned explicitly or implicitly based on conscious awareness of the sequence. Interference happens when two sequences are learned successively. Here, we aimed to determine whether implicit and explicit sequence learning are affected differently by retrograde interference. Young healthy volunteers participated in either a control or interference group and either an explicit or implicit learning condition. We used a modified serial reaction time task to induce sequence learning and control awareness. Results showed that the overall amount of sequence learning was greater in the explicit condition compared to implicit. However, sequence learning was equally susceptible to retrograde interference under either condition. We conclude that although susceptible to interference, explicit awareness improves overall sequence learning compared to implicit conditions.     

Performing the unexplainable: Implicit task performance reveals individually reliable sequence learning without explicit knowledge

Memory-impaired patients express intact implicit perceptual-motor sequence learning, but it has been difficult to obtain a similarly clear dissociation in healthy participants. When explicit memory is intact, participants acquire some explicit knowledge and performance improvements from implicit learning may be subtle. Therefore, it is difficult to determine whether performance exceeds what could be expected on the basis of the concomitant explicit knowledge. Using a challenging new sequence-learning task, robust implicit learning was found in healthy participants with virtually no associated explicit knowledge. Participants trained on a repeating sequence that was selected randomly from a set of five. On a performance test of all five sequences, performance was best on the trained sequence, and two-thirds of the participants exhibited individually reliable improvement (by chi-square analysis). Participants could not reliably indicate which sequence had been trained by either recognition or recall. Only by expressing their knowledge via performance were participants able to indicate which sequence they had learned.     

Implicit learning of semantic category sequences: response-independent acquisition of abstract sequential regularities

Through the use of a new serial naming task, the authors investigated implicit learning of repeating sequences of abstract semantic categories. Participants named objects (e.g., table, shirt) appearing in random order. Unbeknownst to them, the semantic categories of the objects (e.g., furniture, clothing) followed a repeating sequence. Irrespective of whether participants were instructed to attend to the categories (Experiment 1) or whether no mention was made of the categories (Experiments 2 and 3), naming latencies reliably increased when the repeating category sequence was switched to a random sequence. This was the case even for participants showing no explicit knowledge in reproduction and recognition tests. Results indicate that abstract sequential structures are learned implicitly, even if neither the surface stimuli nor the responses follow a sequence.     

Chimpanzee gaze following in an object-choice task

Many primate species reliably track and follow the visual gaze of conspecifics and humans, even to locations above and behind the subject. However, it is not clear whether primates follow a human’s gaze to find hidden food under one of two containers in an object-choice task. In a series of experiments six adult female chimpanzees followed a human’s gaze (head and eye direction) to a distal location in space above and behind them, and checked back to the human’s face when they did not find anything interesting or unusual. This study also assessed whether these same subjects would also use the human’s gaze in an object-choice task with three types of occluders: barriers, tubes, and bowls. Barriers and tubes permitted the experimenter to see their contents (i.e., food) whereas bowls did not. Chimpanzees used the human’s gaze direction to choose the tube or barrier containing food but they did not use the human’s gaze to decide between bowls. Our findings allowed us to discard both simple orientation and understanding seeing-knowing in others as the explanations for gaze following in chimpanzees. However, they did not allow us to conclusively choose between orientation combined with foraging tendencies and understanding seeing in others. One interesting possibility raised by these results is that studies in which the human cannot see the reward at the time of subject choice may potentially be underestimating chimpanzees’ social knowledge. Received: 16 February 1998 / Accepted after revision: 5 July 1998