Performance Dip in motor response induced by task-irrelevant weaker coherent visual motion signals

The Performance Dip is a newly characterized behavioral phenomenon, where, paradoxically, a weaker task-irrelevant visual stimulus causes larger disturbances on the accuracy of a main letter identification task than a stronger stimulus does. Understanding mechanisms of the Performance Dip may provide insight into unconsciousness behavior. Here, we investigated the generalization of the Performance Dip. Specifically, we tested whether the Performance Dip occurs in a motion-related Simon task, and if so, whether the Performance Dip involves the same brain region, that is, the dorsolateral prefrontal cortex (DLPFC), previously implicated in the Performance Dip, or the supplementary motor area (SMA) and pre-SMA, implicated in a motion-related Simon Task. Subjects made manual directional responses according to the color of stochastic moving dots while ignoring the global direction of moving dots, which could be either congruent or incongruent to the response appropriate to the main task. We found that weak incongruent task-irrelevant stimuli caused a Performance Dip, in which the SMA and pre-SMA, rather than DLPFC, played critical roles. Our results suggest a possible common brain mechanism across different neural circuits, in which weak, but not strong, task-irrelevant information is free from inhibition and intrudes into neural circuits relevant to the main task.

Novelty vs. Familiarity Principles in Preference Decisions: Task-Context of Past Experience Matters

Our preferences are shaped by past experience in many ways, but a systematic understanding of the factors is yet to be achieved. For example, studies of the mere exposure effect show that experience with an item leads to increased liking (familiarity preference), but the exact opposite tendency is found in other studies utilizing dishabituation (novelty preference). Recently, it has been found that image category affects whether familiarity or novelty preference emerges from repeated stimulus exposure (Park et al., 2010). Faces elicited familiarity preference, but natural scenes elicited novelty preference. In their task, preference judgments were made throughout all exposures, raising the question of whether the task-context during exposure was involved. We adapt their paradigm, testing if passive exposure or objective judgment task-contexts lead to different results. Results showed that after passive viewing, familiar faces were preferred, but no preference bias in either direction was found with natural scenes, or with geometric figures (control). After exposure during the objective judgment task, familiar faces were preferred, novel natural scenes were preferred, and no preference bias was found with geometric figures. The overall results replicate the segregation of preference biases across object categories and suggest that the preference for familiar faces and novel natural scenes are modulated by task-context memory at different processing levels or selection involvement. Possible underlying mechanisms of the two types of preferences are discussed.

Swayed by the music: sampling bias towards musical preference distinguishes like from dislike decisions

This study investigated the interaction between sampling behavior and preference formation underlying subjective decision making for like and dislike decisions. Two-alternative forced-choice tasks were used with closely-matched musical excerpts and the participants were free to listen and re-listen, i.e. to sample and resample each excerpt, until they reached a decision. We predicted that for decisions involving resampling, a sampling bias would be observed before the moment of conscious decision for the like decision only. The results indeed showed a gradually increasing sampling bias favouring the choice (73%) before the moment of overt response for like decisions. Such a bias was absent for dislike decisions. Furthermore, the participants reported stronger relative preferences for like decisions as compared to dislike decisions. This study demonstrated distinct differences in preference formation between like and dislike decisions, both in the implicit orienting/sampling processes prior to the conscious decision and in the subjective evaluation afterwards.

An integration of color and motion information in visual scene analyses

To analyze complex scenes efficiently, the human visual system performs perceptual groupings based on various features (e.g., color and motion) of the visual elements in a scene. Although previous studies demonstrated that such groupings can be based on a single feature (e.g., either color or motion information), here we show that the visual system also performs scene analyses based on a combination of two features. We presented subjects with a mixture of red and green dots moving in various directions. Although the pairings between color and motion information were variable across the dots (e.g., one red dot moved upward while another moved rightward), subjects' perceptions of the color-motion pairings were significantly biased when the randomly paired dots were flanked by additional dots with consistent color-motion pairings. These results indicate that the visual system resolves local ambiguities in color-motion pairings using unambiguous pairings in surrounds, demonstrating a new type of scene analysis based on the combination of two featural cues.

Overlapping responses for the expectation of juice and money rewards in human ventromedial prefrontal cortex

Although much is known about the neural substrates of reward, the question of whether expectation of different types of reinforcers engage distinct or overlapping brain circuitry has not been addressed definitively. In the present study, human subjects, while being scanned with functional magnetic resonance imaging, performed a simple reward-based action selection task to obtain different magnitudes of either monetary outcomes (winning or losing money) or juice outcomes (pleasant apple juice or an unpleasant salt flavor). At the group level, we found partially overlapping value-related activity within ventromedial prefrontal cortex (vmPFC) during anticipation of juice and money reward outcomes. Analogous results were found in the right anterior insula, except that this region showed negative correlations as a function of increasing expected reward. These results indicate that vmPFC and anterior insula contain overlapping representations of anticipatory value, consistent with the existence of a common currency for the value of expected outcomes in these regions.

Human wagering behavior depends on opponents' faces

Research in competitive games has exclusively focused on how opponent models are developed through previous outcomes and how peoples' decisions relate to normative predictions. Little is known about how rapid impressions of opponents operate and influence behavior in competitive economic situations, although such subjective impressions have been shown to influence cooperative decision-making. This study investigates whether an opponent's face influences players' wagering decisions in a zero-sum game with hidden information. Participants made risky choices in a simplified poker task while being presented opponents whose faces differentially correlated with subjective impressions of trust. Surprisingly, we find that threatening face information has little influence on wagering behavior, but faces relaying positive emotional characteristics impact peoples' decisions. Thus, people took significantly longer and made more mistakes against emotionally positive opponents. Differences in reaction times and percent correct were greatest around the optimal decision boundary, indicating that face information is predominantly used when making decisions during medium-value gambles. Mistakes against emotionally positive opponents resulted from increased folding rates, suggesting that participants may have believed that these opponents were betting with hands of greater value than other opponents. According to these results, the best "poker face" for bluffing may not be a neutral face, but rather a face that contains emotional correlates of trustworthiness. Moreover, it suggests that rapid impressions of an opponent play an important role in competitive games, especially when people have little or no experience with an opponent.