Researchers at Dartmouth have unveiled a remarkable ability of octopuses, showcasing their sophisticated spatial reasoning. A recent study published in Current Biology reveals that these intelligent invertebrates can learn to utilize mirrors to locate food that is not directly visible.
Lead author Mary Kieseler, a PhD graduate from Dartmouth's Department of Psychological and Brain Sciences, now a postdoctoral researcher at the University of Fribourg in Switzerland, states, "Our findings are the first to demonstrate that invertebrates can use mirrors to understand their environment and locate prey." This skill was previously documented only in vertebrates, including certain mammals and birds.
Learning Through Reflection
The research team focused on three California two-spot octopuses (Octopus bimaculoides) in Dartmouth's Octopus Lab. Their objective was to determine if these animals could learn to use a mirror to identify the position of hidden food. Rather than attacking their reflection, the octopuses had to discern the actual location of the food and navigate towards it.
Initially, the octopuses were allowed to acclimate to a mirror placed in their habitat. Subsequently, they were trained to comprehend the connection between their reflection and the real world. In one exercise, a live crab was placed in a glass jar, visible only through the mirror. To access the crab, the octopus had to turn 90 degrees and maneuver around a corner.
"Just as new drivers learn to use a rearview mirror, octopuses can learn to utilize mirrors to infer the location of objects in their environment," explains Peter Tse, senior author and cognitive neuroscientist at Dartmouth.
Assessing Spatial Awareness
To ensure accurate results, researchers used a virtual crab image instead of real prey, as octopuses have chemoreceptors that allow them to smell and taste through touch. Each octopus was placed in a start box with an open front and top, and a mirror positioned directly in front of it. The virtual crab image appeared behind the octopus, visible only through the mirror.
To gain a reward, the octopus needed to identify the actual location of the image and move towards it. Remarkably, the octopuses chose the correct side approximately 73% of the time, demonstrating their ability to navigate based on the reflection.
The researchers monitored the octopuses' movements and noted that while they did not always take the shortest route, they became more efficient at reaching the correct location over time.
Insights into Intelligence Evolution
This study offers intriguing insights into the evolution of intelligence. "Octopuses are among the most evolutionarily distant animals from humans," Kieseler notes. "The ability of such a distant organism to independently evolve mirror use for spatial cognition suggests that similar cognitive processes may arise through convergent evolution across different species."
As octopuses inhabit complex environments like coral reefs, a mental map of their surroundings could enhance their hunting strategies. "Hunters thrive when they possess a mental representation of their territory," Tse adds. This research indicates that octopuses may also maintain internal maps of their environment, further enriching our understanding of their remarkable capabilities.