Scientists Discover a “Shy” Plant That Can Count Without a Brain, and It May Be Smarter Than We Thought

Key Points:

• Researchers at William & Mary, led by psychology professor Peter Vishton and former student Paige Bartosh, found that Mimosa pudica plants can count discrete environmental events, specifically light-and-dark cycles, challenging the assumption that enumeration requires a nervous system.
• The plants exhibited anticipatory leaf movements aligned with a repeating three-day light-dark cycle, showing learning patterns similar to those observed in animals, with increased movement before expected light periods on days with light and decreased movement on days without.
• Experiments altering day length and introducing random cycle durations demonstrated that the plants’ behavior was not governed by a fixed circadian clock but rather by tracking the number of light events within a certain time window, indicating a form of event counting.
• This cognitive-like function occurs without neurons, as Mimosa pudica’s leaf movements are controlled by pulvini cells regulating turgor pressure through ionic exchanges, suggesting unknown biochemical and cellular mechanisms underpin this behavior.
• While the findings are promising, the researchers acknowledge variability in results and call for further replication and mechanistic studies to confirm and better understand the processes involved.