Chimpanzees are our closest living relatives. Like us, they are incredibly smart, have complex personalities that last a lifetime, and even wage violent wars for selfish gain. Now new research published in Personality Neuroscience has discovered that chimp personality traits are linked to the size of a certain structure in the brain – a find that could help us better understand mental illnesses in people.
Renowned primatologist Jane Goodall suggested that chimps have complex personalities and emotional capabilities similar to our own back in the '50s and '60s, after following a chimp community in Tanzania’s Gombe National Park. The idea that animals could have personalities didn’t really pick up until the late 1990s, but now we know that chimps can be agreeable, neurotic, empathic, and even psychopathic, among other things.
Recently, researchers led by Georgia State University set out to better understand how chimp personalities are affected by brain structure. Personalities develop as a result of genetic and neural factors but are obviously shaped by societal, cultural, and social effects too. However, because socio-cultural influences can easily be controlled for in chimpanzees, the apes are handy model animals for looking at how our biology affects our personality.
The team looked at brain imaging data and personality scores for 191 captive chimpanzees. In particular, they focused on how personality is linked to the size of two important brain structures – the amygdala and the hippocampus. The amygdala is central to our emotions, while the hippocampus is key to memory.
The researchers were surprised to find no correlation between the amygdala and personality, as it’s so heavily linked to how we feel. “One potential explanation is that the function of the amygdala may matter more than its structure with regards to personality,” lead study author Robert D. Latzman explained.
However, when it came to the hippocampus, the researchers found something interesting. A larger hippocampus was linked to so-called "alpha" behavior – acting in a poorly controlled and agonistic way – and to a lesser extent disinhibition and impulsivity.
“This underscores the importance of the hippocampus not only in regulating emotion, but also in the neurobiological foundation of broader dispositional dimensions (such as an alpha disposition) and fine-grained personality traits (such as impulsivity),” Latzman said.
Alpha traits are also seen in people, and have been linked to various mental health conditions, so the findings could potentially help us develop better treatments and diagnostic techniques for these disorders.
“While individuals who meet diagnostic criteria for the same psychiatric disorders do not always experience the same symptoms, they do generally tend to share the same basic personality traits,” Latzman explained.
“This kind of research could help scientists develop interventions that target the underlying dispositions associated with mental illness.”