Biologists conducting studies on the behavior of social animals found that gene expressions change depending on the situation, so as to modify the overall behavior of the animal. This connection was hinted at in previous studies, dating as back as 1992, and genetics say it's no surprise that genes are influenced by outside factors as well. In addition, they say that the same applies to humans, during social interactions, and that these modifications are among the most important "creators" of personality.
 

Referring to the behavior of birds hearing other birds sing, study co-author David Clayton, a cell and developmental biology and neuroscience professor at the University of Illinois, said "What's more significant to a bird than hearing another bird singing? This is going on in the equivalent of our auditory cortex and association cortex, so this is pretty high-level stuff going on in the brain. And this was happening in more or less real time by very naturalistic stimuli."
 

External factors could set "precedents" inside the brain, as in they leave a trace of what substances were generated in specific situations. When those moments appear again, genes regulate the production of specific proteins, which in turn trigger even more specific genes, which are otherwise suppressed. This fact has been identified with the help of a microarray, a device that allows scientists to follow the expression of multiple genes at the same time.
 

"An appreciation of the idea that differences in gene expression can occur over vastly different time scales helps understand some of the complex relationships between genes, brain and behavior," said entomology and neuroscience professor Gene Robinson, from the University of Illinois, who is also the lead author of the study published in the Science journal.
 

According to Clayton, experiences continue to influence the brain differently each time, because of the change in social factors. In other words, no one will experience the same, exact situation twice in their lifetime. "Experience is constantly coming back in to the level of the DNA and twiddling the dials and the knobs," he added.