Even Without A Brain, Single-Cell Organisms Are Capable of Learning
The ability to learn is linked to living things with a nervous system, made possible with the presence of nerves and neurons, but a recent study shows that other living organisms are also capable of learning even without a brain.
According to the study published in the journal Proceedings to Royal Society B, Physarum polycephalum, or most commonly known as slime molds, can learn to ignore certain chemical threats in its surroundings when in search of food.
Los Angeles Times reported that lead author Romain Boisseau, a master's student studying evolutionary biology at Ecole Normale Superieure in Paris, said, "What's interesting about slime molds is they appear to be simple, because there is only one cell, but they are capable of amazing stuff, things that we thought were only possible with nervous systems or brains."
For the study, the researchers prepared three different obstacle courses with food in the end. The first and second courses were hindered with a bitter but not harmful compound, which is either coffee or quinine, while the third course does not have any hindrance to the food source and served as the control group.
Three different slime molds were put in each course. Researchers then analyzed how fast they are going in response to the obstacles.
After the nine-day experiment, researchers observed that slime molds put in the first and second courses started to move as fast as the control group within six days. When the researchers shuffled the slime molds and the courses, they discovered that the slime mold took some time before speeding through the hindered courses.
The researchers also found out that after two days of not being exposed to either quinine or coffee, the slime molds returns to its usual slow approach.
They then concluded that after reluctantly traveling at first, the slime molds learned that the chemical hindering them is harmless and they began to return to their normal pace.
This process of learning is called habituation. Habituation is a form of learning in which an organism decreases or ceases to respond to a stimulus after repeated presentations.
Due to the distrustful response of slime mold exposed to coffee to quinine, or vice versa, researchers also noted that the habituation of slime molds is only specific to a given substance.
With this discovery, researchers can now better understand the early evolution of learning in living things, especially on single-cell organisms that can adapt and become resistant to some stimuli.