Complex behaviour is associated with animals having nervous systems but decision making and learning also occur in non-neural organisms [1], including singly-nucleated cells [2, 3, 4, 5] and multi-nucleate synctia [6, 7, 8]. Ciliates are single-cell eukaryotes, widely dispersed in aquatic habitats [9], with an extensive behavioural repertoire [10, 11, 12, 13]. In 1906, Herbert Spencer Jennings [14, 15] described in the sessile ciliate Stentor roeseli a hierarchy of responses to repeated stimulation, which are among the most complex behaviours reported for a singlynucleated cell [16, 17]. These results attracted widespread interest [18, 19] and exert continuing fascination [7, 20, 21, 22] but were discredited during the behaviourist orthodoxy by claims of non-reproducibility [23]. These claims were based on experiments with the motile ciliate Stentor coeruleus. We acquired and maintained the correct organism in laboratory culture and used micromanipulation and video microscopy to confirm Jennings' observations. Despite significant individual variation, not addressed by Jennings, S. roeseli exhibits avoidance behaviours in a characteristic hierarchy of bending, ciliary alteration, contractions and detachment, which is distinct from habituation or conditioning. Remarkably, the choice of contraction versus detachment is consistent with a fair coin toss. Such behavioural complexity may have had an evolutionary advantage in protist ecosystems and the ciliate cortex may have provided mechanisms for implement-⇤

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Short CommunicationSome of the problems which have plagued psychiatry and psychology relate to the limitations of our ability to research conditions to any extent that there is a preponderance of connective data to clarify specific differences in conditions. Part of the problem in achieving the best quality of research is that all life functions on a continuum, spanning time and changing over that medium.Most physical medical scientists know that gathering samples of blood, or blood pressure, or other measures must be repeated at This work is licensed under Creative Commons Attribution 4.0 License ANN.MS.ID.000581.