This Animal Has No Head Or Brain But Can Still Learn

In the realm of intelligence, the conventional notion dictates that complex brains or sizable heads are prerequisites for learning. However, a recent discovery challenges this paradigm as scientists unveil the remarkable learning abilities of an animal devoid of both a head and a brain – the brittle star. This enigmatic creature, with its five arms and bundle of nerves, has emerged as an unexpected quick study.

The mechanism at play here is classical conditioning, a form of learning where associations between different stimuli are formed. The originator of this concept, Russian-Soviet scientist Ivan Pavlov, famously demonstrated it with dogs, causing them to associate the sound of a bell with the anticipation of food through repeated pairings. Humans, too, have shown susceptibility to classical conditioning, as seen in experiments where certain sounds prompt unconscious actions, like reaching for a smartphone.

The research team, intrigued by the potential learning capabilities of echinoderms (including starfish, sea urchins, and sea cucumbers), focused their attention on black brittle stars (Ophiocoma echinata). Sixteen of these creatures were placed in individual tanks equipped with cameras to observe their behavior over a span of 10 months.

Half of the brittle stars underwent a training phase where lights were dimmed for 30 minutes each time they were fed their preferred treat – shrimp. The other half received the same amount of shrimp and experienced dimmed lights for the same duration, but crucially, these events did not coincide.

Despite their inclination to stay hidden, a noticeable difference emerged between the trained and untrained brittle stars. The trained group began to venture out from their concealment as soon as the lights dimmed, anticipating the arrival of the delectable shrimp. In essence, they had learned to associate darkness with the prospect of food.

What astonished researchers even more was the fact that the trained brittle stars retained this learned behavior even after a 13-day hiatus from training, during which the lights were dimmed repeatedly without the provision of food.

Lead author Julia Notar expressed the significance of this finding, stating, “Knowing that brittle stars can learn means they’re not just robotic scavengers like little Roombas cleaning up the ocean floor. They’re potentially able to expect and avoid predators or anticipate food because they’re learning about their environment.”

The perplexing aspect lies in how these creatures, devoid of a head or brain, manage to accomplish such a feat. Notar acknowledged the mystery, stating, “People ask me all the time, ‘how do they do it?’ We don’t know yet. But I hope to have more answers in a few years.”

What is clear is that the brittle star’s nervous system operates fundamentally differently from ours. Nerve cords run along each arm, converging near the mouth, but there is no central command center. As Notar explained, “Each of the nerve cords can act independently. It’s like instead of a boss, there’s a committee.”

The revelation of the brittle star’s ability to learn without a traditional brain challenges our preconceptions about intelligence and opens new avenues for understanding the diverse ways in which organisms navigate and adapt to their environments.