“No sex during training!” This may sound familiar to those of you in competitive sports and even more so for professional fighters. A recent study may help us to better establish the link between previous experiences, in this case, a woman’s touch, and how they can influence our potential for aggressive behavior.

Yuan et al employed an elegantly designed series of behavioral and genetic experiments using the common fruit fly. They identified a symmetrical set of male-specific neuronal circuits in each hemisphere of the fly brain, consisting of eight to ten neurons each, that are involved in the dampening of male aggressive behavior following physical contact with the female sex.

The researchers identified this circuitry through investigating whether previous social experiences influenced otherwise expected aggressive behavior when two males are in a sexually competitive environment — i.e. in the presence of a virgin female fly — which makes male flies particularly hostile. What they found was that while prior social interaction with other male flies dampened their baseline aggressive behavior, having previously interacted with a female effectively eradicated the male fly’s aggressive behavior towards other males.

Mutation screening debunked the famous expression from Rocky’s fictional boxing trainer, “women weaken legs”, for fruit flies at least. Housing males in vials with a mutant female that rejects the male’s attempts to mate, prior to moving the male into a male-male aggression promoting environment, also inhibited the aggressive behavior—sex and sexual exhaustion were ruled out. Similarly, visual and olfactory senses were excluded from playing a key role in the observed aggression inhibition. 

So what was it about the females that had these sex-starved flies displaying such calm and affable behavior? The researchers recently identified a male-specific sensory system involving the pheromone-sensing sodium channel ppk29, which is expressed in a specific group of sensory neurons innervating the sensory bristles on the legs of male flies. They suspect that the touch of the female fly induces a neural plastic effect in the brain, through activation of these ppk29 neurons, resulting in the inhibition of the central aggression circuit, with the neuroplastic effects lasting around two days following the female contact.

When further characterizing the neural networks responsible for female touch-dependent modulation of aggressive behavior, a series of gene silencing experiments revealed that the aggression inhibiting ppk29 network was shown to be activated via GABAergic mechanisms. Interestingly GABAergic neurons are involved in the inhibitory gating or modulation and focusing of neuronal activity in anger and aggression circuits in humans.

While no studies have explored the power of the female touch in humans per se, an fMRI study revealed that simply holding your partners hand has been shown to inhibit the stress response when subjected to the threat of mild electric shock. Social interactions undoubtedly influence our behavior, aggression included.

One might argue that in humans there may be some merit to the idea that a woman’s touch, for some, may weaken their competitive, aggressive, fighting spirit. However, humans have complex motivational, emotional and behavioral hierarchies that can be heavily influenced by the environment, prior experience and internal states of being at that present time. Outside of the ring and competitive sport, prospective analogous studies about previous social experiences and their influence on aggression may lead to a deeper understanding of human interpersonal violence.

According to the latest World Health Organization’s Report on Violence and Health, interpersonal violence is a leading cause of death worldwide. For example, in 2000 it was estimated that 565 children, adolescents and young adults between the ages of 10 and 29 years die globally each day as a result of interpersonal violence from members of their family or their community. As such, there is much to be gained from establishing avenues to reduce and prevent aggression and violence; including the current topic of interest, the formidable power of the female touch.

References

Coan JA, Schaefer HS, & Davidson RJ (2006). Lending a hand: social regulation of the neural response to threat. Psychological science, 17 (12), 1032-9 PMID: 17201784

Potegal M (2012). Temporal and frontal lobe initiation and regulation of the top-down escalation of anger and aggression. Behavioural brain research, 231 (2), 386-95 PMID: 22085875

Yuan Q, Song Y, Yang CH, Jan LY, & Jan YN (2014). Female contact modulates male aggression via a sexually dimorphic GABAergic circuit in Drosophila. Nature neuroscience, 17 (1), 81-8 PMID: 24241395

Image via Gulserinak1955 / Shutterstock.