There is nothing paranormal about near-death experiences: how neuroscience can explain seeing bright lights, meeting the dead, or being convinced you are one of them

Approximately 3% of Americans declare to have had a near-death experience. These experiences classically involve the feeling that one's soul has left the body, approaches a bright light and goes to another reality, where love and bliss are all encompassing. Contrary to popular belief, research suggests that there is nothing paranormal about these experiences. Instead, near-death experiences are the manifestation of normal brain function gone awry, during a traumatic, and sometimes harmless, event.     

The role of testosterone in social interaction

Although animal researchers established the role of testosterone as a 'social hormone' decades ago, the investigation of its causal influence on human social behaviors has only recently begun. Here, we review and discuss recent studies showing the causal effects of testosterone on social interactions in animals and humans, and outline the basic neurobiological mechanisms that might underlie these effects. Based on these recent findings, we argue that the role of testosterone in human social behavior might be best understood in terms of the search for, and maintenance of, social status.     

Target animacy influences gorilla handedness

We investigated the unimanual actions of a biological family group of twelve western lowland gorillas (Gorilla gorilla gorilla) using a methodological approach designed to assess behavior within social context from a bottom-up perspective. Measures of both the lateralization of unimanual actions (left, right) and the target of the action (animate, inanimate) were assessed during dual, synchronized video observations of naturalistic behavior. This paper demonstrates a corelationship between handedness and the animate quality of the target object. Analyses demonstrated a significant interaction between lateralized unimanual actions and target animacy and a right-hand bias for actions directed toward inanimate targets. We suggest that lateralized motor preference reflects the different processing capabilities of the left and right hemispheres, as influenced by the emotive (animate) and/or functional (inanimate) characteristics of the target, respectively.     

A sex difference in effect of prior experience on object-mediated problem-solving in gibbons

Understanding the functionally relevant properties of objects is likely facilitated by learning with a critical role for past experience. However, current evidence is conflicting regarding the effect of prior object exposure on acquisition of object manipulation skills. This may be due to the influence of life history variables on the capacity to benefit from such experience. This study assessed effect of task-relevant object exposure on object-mediated problem-solving in 22 gibbons using a raking-in task. Despite not using tools habitually, 14 gibbons spontaneously used a rake to obtain a reward. Having prior experience with the rake in an unrewarded context did not improve learning efficiency in males. However, females benefitted significantly from the opportunity to interact with the rake before testing, with reduced latencies to solution compared to those with no previous exposure. These results reflect potential sex differences in approach to novelty that moderate the possible benefits of prior experience. Due to their relatively high energetic requirements, reproductively active females may be highly motivated to explore potential resources; however, increased investment in developing offspring could make them more guarded in their investigations. Previous exposure that allows females to learn of an object’s neutrality can offset this cautious exploration.     

Aping expressions? Chimpanzees produce distinct laugh types when responding to laughter of others

Humans have the ability to replicate the emotional expressions of others even when they undergo different emotions. Such distinct responses of expressions, especially positive expressions, play a central role in everyday social communication of humans and may give the responding individuals important advantages in cooperation and communication. The present work examined laughter in chimpanzees to test whether nonhuman primates also use their expressions in such distinct ways. The approach was first to examine the form and occurrence of laugh replications (laughter after the laughter of others) and spontaneous laughter of chimpanzees during social play and then to test whether their laugh replications represented laugh-elicited laugh responses (laughter triggered by the laughter of others) by using a quantitative method designed to measure responses in natural social settings. The results of this study indicated that chimpanzees produce laugh-elicited laughter that is distinct in form and occurrence from their spontaneous laughter. These findings provide the first empirical evidence that nonhuman primates have the ability to replicate the expressions of others by producing expressions that differ in their underlying emotions and social implications. The data further showed that the laugh-elicited laugh responses of the subjects were closely linked to play maintenance, suggesting that chimpanzees might gain important cooperative and communicative advantages by responding with laughter to the laughter of their social partners. Notably, some chimpanzee groups of this study responded more with laughter than others, an outcome that provides empirical support of a socialization of expressions in great apes similar to that of humans.     

The nicotinic acetylcholine receptor gene CHRNA4 is associated with negative emotionality

Knock-out studies in mice suggest a role of the CHRNA4 gene in anxiety. In the present study we extend this finding to humans by means of a genetic association study. In a sample of N = 574 healthy White participants, the CHRNA4 rs1044396 polymorphism is related to the common variance of several conceptualizations of negative emotionality. Compared to carriers of at least one T-allele, carriers of the homozygous C/C genotype described themselves as more anxious and emotionally unstable on various psychometric personality questionnaires. The scope of the genetic effect is remarkable because other prominent genetic markers for anxiety show specificity for the diagnostic tool used. The present study is the first study that demonstrates the relevance of the CHRNA4 gene for negative emotionality in humans and sets a starting point for further investigations that could inform on the treatment of various affective psychiatric disorders.     

The role of fear and expectancies in capture of covert attention by spiders

Fear-related stimuli are often prioritized during visual selection but it remains unclear whether capture by salient objects is more likely to occur when individuals fear those objects. In this study, participants with high and low fear of spiders searched for a circle while on some trials a completely irrelevant fear-related (spider) or neutral distractor (butterfly/leaf) was presented simultaneously in the display. Our results show that when you fear spiders and you are not sure whether a spider is going to be present, then any salient distractor (i.e., a butterfly) grabs your attention, suggesting that mere expectation of a spider triggered compulsory monitoring of all irrelevant stimuli. However, neutral stimuli did not grab attention when high spider fearful people knew that a spider could not be present during a block of trials, treating the neutral stimuli just as the low spider fearful people do. Our results show that people that fear spiders inspect potential spider-containing locations in a compulsory fashion even though directing attention to this location is completely irrelevant for the task. Reduction of capture can only be accomplished when people that fear spiders do not expect a spider to be present.