Learning, remembering, and reasoning are generally believed to require a brain. However, a new study by psychologists at William & Mary University challenges this belief.
Scientists have provided evidence that plants are capable of "counting" events and tracking their quantity, despite not possessing a single nerve cell.
Professor Peter Fishton and researcher Paige Bartosh conducted an experiment on the shy mimosa plant (Mimosa pudica), in which the plants were placed in a soundproof room with adjustable lighting in three-day cycles: two days of alternating day and night (12 hours each), and a third day of complete darkness. After five cycles, the mimosa showed increased leaf movement before "dawn" on the days when light was expected, while remaining still during the days of total darkness.
To rule out the influence of the biological clock, scientists changed the length of the "day" to range between 20 and 32 hours. When the cycle duration was between 12 and 24 hours, the mimosa adapted precisely to the timing of the light switching on, but when this limit was exceeded, the pattern broke down, indicating a limit to the plants' ability to retain information.
The learning curve in mimosa was also found to be logarithmic, which is consistent with the learning curves of animals such as rats. The researchers hypothesized that learning might be a characteristic common to all living cells, especially since something resembling visual perception has previously been observed in plants.
These results open up prospects for the development of biological computing devices and the creation of new methods for treating addiction, but the mechanisms of "brainless memory" still need further research and study.
