Minimal cognition in unicellular organisms

The evolutionary roots of cognition are older than any brain. Human or primate-centered cognitive science tends to ignore that words like "mind" and other psychological constructs, e.g. association, remembering, forgetting, learning etc. describe cellular and cellular-network activities, not entities existing separately from cells. Such activities are found throughout all living organisms, even in those not possessing nerve cells. In the search for a minimum in structure and function of cognition, we strongly suggest taking a closer look at unicellular organisms and, in particular, at bacteria and their behavior. Bacteria and other unicellular organisms are autonomous and social beings showing (the lowest level of) cognition. They have the fundamental cognitive abilities to identify elements of the environment and to differentiate between them (and self), to choose among alternatives, to adapt to changes, to coordinate their behavior in groups, to act purposefully. These capabilities are primary biological functions. In this respect and because bacteria are the oldest known living systems, life and cognition can be considered to be synonymous. Their study should be a starting point for cognitive science. At the individual (single cell) level, minimality is a matter of number, type and distribution (spacing) of sensors (receptors) and effectors, of changes between spontaneous and stimulated reactions, of sequential (temporal) and/or simultaneous (spatial) sampling, of modulation and duration of feedback processes (adaptation and habituation). At the population level minimality is also related to the production and processing of communication signals for group behavior and to the types of interconnection among single individuals (cells)