Decline in executive control during acute bouts of exercise as a function of exercise intensity and fitness level

Studies on the effects of acute bouts of cardiovascular exercise on cognitive performances show contradictory findings due to methodological differences (e.g., exercise intensity, cognitive function assessed, participants’ aerobic fitness level, etc.). The present study assessed the acute effect of exercise intensity on cognition while controlling for key methodological confounds. Thirty-seven participants (M_age = 23. 8 years; SD = 2.6) completed a computerized modified-Stroop task (involving denomination, inhibition and switching conditions) while pedalling at 40%, 60% and 80% of their peak power output (PPO). Results showed that in the switching condition of the task, error rates increased as a function of exercise intensity (from 60% to 80% of PPO) in all participants and that lower fit individuals showed increased reaction time variability. This suggests that acute bouts of cardiovascular exercise can momentarily alter executive control and increase performance instability in lower fit individuals.     

Frequency-shift detectors bind binaural as well as monaural frequency representations

Previous psychophysical work provided evidence for the existence of automatic frequency-shift detectors (FSDs) that establish perceptual links between successive sounds. In this study, we investigated the characteristics of the FSDs with respect to the binaural system. Listeners were presented with sound sequences consisting of a chord of pure tones followed by a single test tone. Two tasks were performed. In the "present/absent" task, the test tone was either identical to one of the chord components or positioned halfway in frequency between two components, and listeners had to discriminate between these two possibilities. In the "up/down" task, the test tone was slightly different in frequency from one of the chord components and listeners had to identify the direction (up or down) of the corresponding shift. When the test tone was a pure tone presented monaurally, either to the same ear as the chord or to the opposite ear, listeners performed the up/down task better than the present/absent task. This paradoxical advantage for directional frequency shifts, providing evidence for FSDs, persisted when the test tone was replaced by a dichotic stimulus consisting of noise but evoking a pitch sensation as a consequence of binaural processing. Performance in the up/down task was similar for the dichotic stimulus and for a monaural narrow-band noise matched in pitch salience to it. Our results indicate that the FSDs are insensitive to sound localization mechanisms and operate on central frequency representations, at or above the level of convergence of the monaural auditory pathways.     

Does group identification facilitate or prevent collective guilt about past misdeeds? Resolving the paradox

The influence of group identification on collective guilt and attitudes towards reparation was examined in the context of the Belgian colonization of Congo. People should experience collective emotions to the extent that being a member of the relevant group is part of their self-concept. Yet, the acknowledgement of ingroup responsibility for past misdeeds is particularly threatening for high identifiers and may lead to defensive reactions aimed at avoiding guilt. We therefore predicted, and found, a curvilinear effect of identification on collective guilt. Attitudes towards reparation of past wrongdoings were also assessed and yielded a linear trend: identification predicted less favourable attitudes towards reparation but this effect was marginally stronger as identification increased.     

Closed-loop bird–computer interactions: a new method to study the role of bird calls

In the field of songbird research, many studies have shown the role of male songs in territorial defense and courtship. Calling, another important acoustic communication signal, has received much less attention, however, because calls are assumed to contain less information about the emitter than songs do. Birdcall repertoire is diverse, and the role of calls has been found to be significant in the area of social interaction, for example, in pair, family, and group cohesion. However, standard methods for studying calls do not allow precise and systematic study of their role in communication. We propose herein a new method to study bird vocal interaction. A closed-loop computer system interacts with canaries, Serinus canaria, by (1) automatically classifying two basic types of canary vocalization, single versus repeated calls, as they are produced by the subject, and (2) responding with a preprogrammed call type recorded from another bird. This computerized animal–machine interaction requires no human interference. We show first that the birds do engage in sustained interactions with the system, by studying the rate of single and repeated calls for various programmed protocols. We then show that female canaries differentially use single and repeated calls. First, they produce significantly more single than repeated calls, and second, the rate of single calls is associated with the context in which they interact, whereas repeated calls are context independent. This experiment is the first illustration of how closed-loop bird–computer interaction can be used productively to study social relationships.     

Cognitive dissonance induced by writing a counterattitudinal essay facilitates performance on simple tasks but not on complex tasks that involve working memory

This article examines how performance is facilitated with simple tasks and is impaired with complex ones in individuals experiencing dissonance. Experiment 1 measured the performance of dissonance participants at a simple reaction time task. Reaction times were shortest in the dissonance condition. This facilitation effect was interpreted as resulting from increased arousal with dissonance. In Experiment 2, participants performed a more complex secondary memory task that required to memorize and to recall short and long series of numbers. Participants in the dissonance condition performed less well than participants in the no-dissonance condition only under a high memory load and did not differ with a low load. It is suggested that dissonance requires some working memory resources. Accordingly, it is assumed that the arousal properties of dissonance facilitate performance with simple task that do not involve working memory and require a dominant response, but that dissonance impairs performance with tasks that strongly involve working memory.     

Influence of authoritarianism,vagal tone and mental fatigue on obedience to authority

Recent research suggests that obedience in the Milgram paradigm is underpinned by stress vulnerability and inhibitory control over pain sharing. Because self-regulatory fatigue (SRF) induction is a suited method to investigate the influence of inhibitory control on behaviour, participants (n?=?99) were randomly assigned to a High vs. Low self-regulatory condition. Heart rate variability (HRV, a biomarker of stress vulnerability) was collected during 5-min baseline and continuously during the experimental procedure. Prior to the experiment, participants completed an online survey assessing right-wing authoritarianism (RWA), a well-known predictor of obedience. Using the Immersive Video Milgram Obedience Experiment, we found (i) that lower resting HRV predicted higher destructive obedience, (ii) that low self-regulatory inhibition (induced by fatigue) reduced destructive obedience, (iii) that the well-established influence of RWA on destructive obedience was suppressed in the presence of SRF. Implications for future directions in obedience research are discussed.     

The slow formation of a pitch percept beyond the ending time of a short tone burst

The discriminability of short tone bursts differing in frequency was measured in terms of the sensitivity index d' as a function of interstimulus interval (ISI). The two stimuli presented on each trial consisted of either 6 or 30 sinusoidal cycles. When the frequency of the first stimulus varied randomly and widely from trial to trial (Experiment 1), discriminability was maximal for an ISI of about 400 msec in the 6-cycles condition and for a significantly longer ISI (of about 1 sec) in the 30-cycles condition. However, when the first stimulus had only two possible frequencies and the second stimulus was fixed (Experiment 2), the optimal ISI appeared to be about 400 msec in both conditions. A final experiment confirmed that, for tone bursts of 30 cycles, the optimal ISI was dependent on the perceptual uncertainty of the first stimulus. These results support the idea that the duration required to perceive the pitch of a sound as accurately as possible may far exceed the duration of the stimulus itself. More importantly, they indicate that the required duration is not a constant.     

The neural code for written words: a proposal

How is reading, a cultural invention, coded by neural populations in the human brain? The neural code for written words must be abstract, because we can recognize words regardless of their location, font and size. Yet it must also be exquisitely sensitive to letter identity and letter order. Most existing coding schemes are insufficiently invariant or incompatible with the constraints of the visual system. We propose a tentative neuronal model according to which part of the occipito-temporal 'what' pathway is tuned to writing and forms a hierarchy of local combination detectors sensitive to increasingly larger fragments of words. Our proposal can explain why the detection of 'open bigrams' (ordered pairs of letters) constitutes an important stage in visual word recognition.     

The interplay of attention and bimanual coordination dynamics

Despite their common origin, studies on motor coordination and on attentional load have developed into separate fields of investigation, bringing out findings, methods, and theories which are diverse if not mutually exclusive. Sitting at the intersection of these two fields, this article addresses the issue of behavioral flexibility by investigating how intention modifies the stability of existing patterns of coordination between moving limbs. It addresses the issue, largely ignored until now, of the attentional cost incurred by the central nervous system (CNS) in maintaining a coordination pattern at a given level of stability, in particular under different attentional priority requirements. The experimental paradigm adopted in these studies provides an original mix of a classical measure of attentional load, namely, reaction time, and of a dynamic approach to coordination, most suitable for characterizing the dynamic properties of coordinated behavior and behavioral change. Findings showed that central cost and pattern stability covary, suggesting that bimanual coordination and the attentional activity of the CNS involved in maintaining such a coordination bear on the same underlying dynamics. Such a conclusion provides a strong support to a unified approach to coordination encompassing a conceptualization in terms of information processing and another, more recent framework rooted in self-organization theories and dynamical systems models     

Visual information and skill level in time-to-collision estimation

Previous studies on the visual origin of time-to-collision (Tc) information have demonstrated that Tc estimates can be based solely on the processing of target expansion rate (optic variable tau). But in the simulated situations used (film clips), there was little reliable information on speed (owing to reduced peripheral vision) and distance (owing to the absence of binocular distance cues) available. In order to determine whether these kinds of information are also taken into account, it is necessary to take an approach where the subject receives a more complete visual input. Thus, an experiment conducted on a circuit under actual driving conditions is reported. Experienced drivers and beginners, who were passengers in a car, had to indicate the moment they expected a collision with a stationary obstacle to take place. Subjects were blindfolded after a viewing time of 3 s. The conditions for speed evaluation (normal versus restricted visual field) and distance evaluation (binocular versus monocular vision) by subjects were varied. The approach speed (30 and 90 km h-1) and actual Tc (3 and 6 s) were also varied. The results show that accuracy of Tc estimation increased with (i) normal visual field, (ii) binocular vision, (iii) higher speeds, and (iv) driving experience. These findings have been interpreted as indicating that both speed and distance information are taken into account in Tc estimation. They suggest furthermore that these two kinds of information may be used differently depending on the skill level of the subject. The results are discussed in terms of the complementarity of the various potentially usable visual means of obtaining Tc information.