The use of Virtual Reality (VR) in interactive studies is becoming increasingly popular. Despite its popularity to use Virtual Characters (VC) instead of confederates in VR studies, the effect of...Show moreThe use of Virtual Reality (VR) in interactive studies is becoming increasingly popular. Despite its popularity to use Virtual Characters (VC) instead of confederates in VR studies, the effect of VCs on humans has not been sufficiently studied yet, especially regarding scratching behaviour. The present explores the effect of the presence or absence of a VC on humans’ scratching behaviour. There are two rationales behind the assumption that VCs affect scratching behaviour. The first is that scratching is shown more frequently under stress, but the presence of VCs can reduce stress. The second one is that participants want to adhere to social norms in front of a VC, which condemn scratching. For the present study, participants (n = 38) were immersed in a virtual environment using a Head-Mounted-Display. They had to describe itch-inducing pictures either while a VC was present or absent. The frequency and duration of the scratching behaviour of participants were recorded. Two two-sided paired t-tests were conducted to compare both scratch frequency and scratch duration in the VC present versus the VC absent condition. The findings show that the participants scratched less often and with a shorter duration when the VC was present compared to when the VC was absent, indicating that the presence of VCs can alter humans’ scratch behaviour. The results of this study can help to establish the use of VCs further and lay the foundation for a more in-depth investigation into scratch behaviour using virtual environments. However, more research is needed to investigate the underlying reasons for the observed behaviour.Show less
The prospect of reward has increasingly been shown to influence modes of cognitive control. Recent work by Fröber and Dreisbach (2016) showed that performance contingent reward increases proactive...Show moreThe prospect of reward has increasingly been shown to influence modes of cognitive control. Recent work by Fröber and Dreisbach (2016) showed that performance contingent reward increases proactive control, while non-contingent reward decreases proactive control and possibly increases reactive control. According to the Metacontrol State Model (Hommel, 2015), the differential effects of reward on cognitive control can be understood as a tradeoff between cognitive persistence and flexibility. Persistence refers to a mode of control that allows for strong maintenance of goal-relevant information and the suppression of irrelevant information, while flexibility refers to a mode of control that facilitates switching between tasks by allowing for more efficient consideration of irrelevant information. While evidence suggests that contingent reward promotes persistence and non-contingent reward decreases persistence, it is not clear whether non-contingent reward promotes flexibility. The aim of the present study was to expand on previous findings by investigating whether contingent reward promotes persistence and whether non-contingent reward promotes flexibility, by employing two cognitive tasks that presumably benefit from either persistence or flexibility, namely the Simon task and the Attentional Blink task. Participants were allocated to three conditions (e.g., contingent, non-contingent, and control) and performed both tasks in a single session. Participant allocation and task completion were counterbalanced. Both performance contingent and non-contingent reward promoted cognitive flexibility in the Simon task, or at least decreased cognitive persistence, but had no effect in the Attentional blink task. While these results support the general finding that reward differentially modulates cognitive control, they further underline the importance of considering the cognitive paradigm used to assess changes in cognitive control.Show less
Recent insights into the role of the human microbiota on the brain and cognitive functioning have led to the hypothesis that the probiotic ‘Ecologic Barrier’ may decrease aggressive behavior and/or...Show moreRecent insights into the role of the human microbiota on the brain and cognitive functioning have led to the hypothesis that the probiotic ‘Ecologic Barrier’ may decrease aggressive behavior and/or thoughts. The aim of the current study was to investigate the effect of a 4-week multispecies probiotic intervention on self-reported aggressive behavior and thought patterns in healthy individuals, whether there are differences between males and females, and to investigate whether HRV has an influence on the efficacy of the intervention with probiotics. HRV is a physiological phenomenon of the variation in the time interval between heartbeats. Low HRV can be related to impaired behavioral regulation and reduced behavioral inhibition, which is related to aggressive behavior, and therefore this can be a mediating variable in the design of this study. Individuals with a low HRV could benefit more from the intervention with probiotics than individuals with a high HRV and could expect a greater decrease in aggressive behavior and/or thoughts. In a double-blind, placebo-controlled, randomized, pre-and post-intervention assessment, between-subjects design, 25 healthy participants received a 4-week probiotic food-supplement intervention with the multispecies probiotics, while 25 control participants received an inert placebo for the same period. In the pre- and post-intervention assessment, self-reported aggressive behavior and thoughts were assessed using the Aggression Questionnaire and the aggression subscale of the LEIDS-r, the Leiden Index for Depression Sensitivity. The 4-week multispecies probiotic intervention did not reduce physical aggression, verbal aggression, anger, hostility, overall aggression scores or aggressive thought patterns. A slight decrease in aggressive behavior and aggressive thoughts can be seen on a few subscales in the probiotics group, but the results were not significant. An exploratory finding was found: participants with a decreased HRV compared to the pre-intervention measurement, scored higher on verbal aggression during the post-intervention; a strong negative correlation was found. However, HRV appeared to have no influence on the efficacy of the intervention with probiotics. These results provide evidence that a low HRV could be linked to higher verbal aggression. Previous research has shown that there could be a difference in aggression between men and women, for example through male hormones, and therefore future studies should investigate why self-reported aggressive behavior and thoughts in males and females may respond differently to probiotics. The sample used for this study was pre-dominantly female and this could be an explanation for the fact that no difference was found. This study has some limitations that may have led to these results. A lot of research has been done on mice, research that cannot simply be translated into humans. This study did not include the exact influence of stress and the use of HRV, regulated by efferent fibers of the vagal nerve, to determine the influence and effectiveness of probiotics can be questioned because probiotics activate the afferent fibers of the vagal nerve . Furthermore, we work with self-reported aggressive behavior among participants without clinical aggression scores. In the future, research could be done into the influence of probiotics on aggression within the clinical population.Show less
