Abstract

The study of plant signaling and behaviour, whose aim is to address the physiological basis for adaptive behaviour in plants, is a growing and thought-provoking field of research. In this review we discuss relevant studies that try to interpret in a neurocognitive fashion cases in which plants seem to behave similarly to animals. By comparing observations and experiments about plants and animals, we propose a framework composed of three axes in which interactions of living organisms with the world can be represented. The first axis refers to adaptiveness, the second to sensitivity, and the third to sentience. This model allows us to interpret the behaviours of living organisms along a continuum capable of giving a smooth transition from simple to complex responses. In light of this, plants show an excellent adaptiveness, a variable level of sensitivity, and a good degree of sentience (restricted to the immediate perception that something is happening to themselves). Only the organisms with a high degree of sentience can have the basis for developing consciousness. However, even though it is necessary for consciousness, sentience is not sufficient, as it must be associated with a complex functional organization of structures that can support a recursive and synchronized processing of information. So far, plants have been found to completely lack this type of organization. Plants appear to be, therefore, sentient but not conscious.