A simple drinking glass has been used for eons to gauge your personality type. Are you a pessimist? Half empty, obviously. Of course, making this a binary decision is part of the problem. The totality of your emotional response system cannot be weighed by judging a half of a glass.
Yet how we respond to the circumstances we encounter is telling. Optimism and pessimism are traits that in part define our reality. Being hopeful about the future is often the best path forward, though skeptics apply better critical thinking skills, helping them avert potential dangers. As with everything in life, balance is key.
That said, rampant pessimism underlies diseases of anxiety and depression. While there is no known cause (or cure) for such an outlook on life, researchers from MIT and Kyoto University decided to investigate whether a specific brain region can be implicated in fomenting pessimism. They believe they might have found it.
For the study, published in the journal, Neuron, researchers used approach-avoidance (Ap-Av) conflict on a group of macaques to identify neural regions involved in pessimistic decision making. The Ap-Av conflict test is a well-studied means for invoking anxious behavior; increased stress causes animals to choose higher-risk and higher-payoff options.
The research team, led by MIT’s McGovern Institute research affiliates Ken-ichi Amemori and Satoko Amemori, located the mechanism in the brain’s caudate nucleus (CN):
We here hypothesize that the primate CN could be causally involved in the generation of persistent and repetitive negative states, and that neural activity in the CN could exhibit specific features correlated with these states.
The CN is part of the striatum region, located in the dorsal striatum, alongside the putamen, which is known to regulate movement and influence certain types of learning. The striatum coordinates numerous aspects of cognition, most significantly motor and action planning, decision making, and reinforcement. It is also part of the brain’s reward network, where dopamine is a major player. The researchers identified this system as the main culprit in promoting pessimistic behavior:
Our findings suggest that local striatal circuits could be causal sources in producing persistent pessimistic states, and that striatal beta oscillation could be a neural correlate of the persistent states.
Pessimistic traits in humans cause ritualistic behavior. Whenever confronting a situation, the pessimist is likely to focus on the potential negative outcome. Though again, this could be helpful—for example, in financial decisions, or when weighing whether or not to date someone when you notice troubling signs of behavior. But this approach can also be crippling. The risk-averse rarely succeed in endeavors that call for a faith in one’s abilities; when you’re always choosing the negative outcome, it’s unlikely you’ll progress in your career or love.
Regions of the CN are linked to the limbic system, where your mood is regulated. Again, dopamine appears. When decisions are called for, pessimists were noticed to have specific brainwave activity in the CN that altered their behavior, which affected dopamine output. When the researchers purposefully suppressed dopamine activity in these regions, they noticed changes in the cost-benefit analysis of the macaques.
The surprisingly strong changes in evaluative decision-making that we have found by sub-cortical microstimulation, and the specificity of induction of long-lasting states of negative evaluation associated with selective beta-band patterning during decision-making, point to the striatum as a potentially powerful driver for the induction of mood changes including excessive and persistent pessimism.
Senior author of the study, MIT Institute Professor Ann Graybiel, says that the complexity of the systems requires a “delicate balance”:
There must be many circuits involved. But apparently we are so delicately balanced that just throwing the system off a little bit can rapidly change behavior.
The researchers hope this will help lead to breakthroughs in treating anxiety, depression, and obsessive-compulsive disorder, which also creates ritualistic behavior. If micro-stimulation can help the sufferer finally break the glass, they’ll no longer have to worry about how much liquid remains.