Yesterday we reported on a new study that showed shining a laser on certain neurons in mice brains could make them angry and aggressive. But with squid, you don’t need a laser to make the males get mean. All you need is to expose them to a particular chemical. From DISCOVER blogger Ed Yong:
In a flash, schools of male longfin squid can turn from peaceful gatherings to violent mobs. One minute, individuals are swimming together in peace; the next, they’re attacking one another. The males give chase, ramming each other in the sides and grappling with their tentacles.
These sudden bouts of violence are the doing of the female squid. Males are attracted to the sight of eggs, and females lace the eggs with a chemical that transforms the males into aggressive brutes.
For plenty more about how this chemical whips the males into an angry frenzy—and why—check out the rest of Ed’s post at Not Exactly Rocket Science.
Not Exactly Rocket Science: A Squid’s Beak is a Marvel of Biological Engineering
Not Exactly Rocket Science: Tears as chemical signals – smell of female tears affects sexual behaviour of men
80beats: A Blast of Light to the Brain Can Make Mice Mean
The burgeoning field of optogenetics—using shot of light on neurons to control behavior—has already produced some intruiging and peculiar results. Now add one more: Scientists can use it to make mice angry and aggressive.
With a pulse of light, Dayu Lin from New York University can turn docile mice into violent fighters – it’s Dr Jekyll’s potion, delivered via fibre optic cable. The light activates a group of neurons in the mouse’s brain that are involved in aggressive behaviour. As a result, the mouse attacks other males, females, and even inanimate objects.
Lin focused on a primitive part of the brain called the hypothalamus that keeps our basic bodily functions ticking over. It lords over body temperature, hunger, thirst, sleep and more. In particular, Lin found that a small part of this area – the ventrolateral ventromedial hypothalamus (VMHvl) – acts as a hub for both sex and violence.
Read plenty more about this study in the rest of Ed’s post at Not Exactly Rocket Science.
80beats: Zapping Worm Brains With Lasers Reveals the Duty of Each Neuron
80beats: Star Trek-Style “Phaser” Paralyzes Worms With a UV Blast
80beats: Shiny New Neuroscience Technique (Optogenetics) Verifies a Familiar Method (fMRI)
80beats: Researchers Flip Brain Cells On and Off With Light Pulses
A spike in testosterone may not always turn you into a greedy, aggressive, power hungry monster. According to research led by Ernst Fehr, testosterone’s true effect may be to encourage status-seeking behavior, and it can actually make people play more fairly with others.
What’s more, its biological effects on a person may be overruled by that person’s beliefs. In a game-playing experiment set up by Fehr in which some people received a testosterone shot while others got a placebo, those who suspected they had received bona fide testosterone acted more selfishly than those who believed they got the bogus treatment, no matter what they actually received [New Scientist].
Fehr and colleagues used the ‘ultimatum bargaining’ game to test how testosterone would affect behaviour in a group of 121 women. Counter-intuitively, women who were given testosterone bargained more fairly. But the idea that testosterone causes aggression in humans, as it clearly does in rodents, is so firmly ingrained in the human psyche that women who believed they had been given testosterone — whether or not they had — bargained much less fairly [Nature News]. The researchers tested women because they have little variation in their normal testosterone levels. The authors, who published their work in the journal Nature, say their results essentially debunk the popular wisdom that says testosterone causes aggression. Rather, their findings reinforce another idea–hormones are complicated, and testosterone is no exception.
A new study has dealt a blow to the reputation of bonobos as and the most loving and caring of primates. Researchers following the apes through the forests of the Democratic Republic of Congo observed 5 instances when the bonobos hunted monkeys, including three successful hunts where the apes began devouring their prey even before it was dead. Says lead researcher Gottfried Hohmann: “Bonobos are merciless…. [T]hey catch it and start eating it. They don’t bother to kill it” [New Scientist].
While bonobos primarily eat fruit, researchers have known for some time that the apes supplement their diet with rodents and small antelopes. This study is the first to include other primates in their food supply, a finding that shows them to be surprisingly similar to chimpanzees, who sometimes hunt monkeys. Bonobos are generally considered more peaceful than their close cousins, the chimps, and have a reputation for free-loving ways because sex plays a major role their society, being used for greetings, conflict resolution and reconciliation [Reuters].