title: Ants determine their next move at rest: motor planning and causality in complex systems.
abstract: To find useful work to do for their colony, individual eusocial animals have to move, somehow staying attentive to relevant social information. Recent research on individual Temnothorax albipennis ants moving inside their colony's nest found a power-law relationship between a movement's duration and its average speed; and a universal speed profile for movements showing that they mostly fluctuate around a constant average speed. From this predictability it was inferred that movement durations are somehow determined before the movement itself. Here, we find similar results in lone T. albipennis ants exploring a large arena outside the nest, both when the arena is clean and when it contains chemical information left by previous nest-mates. This implies that these movement characteristics originate from the same individual neural and/or physiological mechanism(s), operating without immediate regard to social influences. However, the presence of pheromones and/or other cues was found to affect the inter-event speed correlations. Hence we suggest that ants' motor planning results in intermittent response to the social environment: movement duration is adjusted in response to social information only between movements, not during them. This environmentally flexible, intermittently responsive movement behaviour points towards a spatially allocated division of labour in this species. It also prompts more general questions on collective animal movement and the role of intermittent causation from higher to lower organizational levels in the stability of complex systems.
authors.affiliation: School of Biological Sciences , University of Bristol, Life Sciences Building , 24 Tyndall Avenue, Bristol BS8 1TQ, UK.
authors.forename: Edmund R
authors.identifier: 0000-0002-9647-124X
authors.initials: ER
authors.lastname: Hunt
authors.affiliation: School of Experimental Psychology , University of Bristol , 12a Priory Road, Bristol BS8 1TU, UK.
authors.forename: Roland J
authors.identifier: 0000-0002-7431-6580
authors.initials: RJ
authors.lastname: Baddeley
authors.affiliation: School of Biological Sciences , University of Bristol, Life Sciences Building , 24 Tyndall Avenue, Bristol BS8 1TQ, UK.
authors.forename: Alan
authors.identifier: 0000-0002-7734-7841
authors.initials: A
authors.lastname: Worley
authors.affiliation: Department of Engineering Design and Mathematics , University of the West of England , Frenchay Campus, Coldharbour Lane, Bristol BS16 1QY, UK.
authors.forename: Ana B
authors.identifier: 0000-0001-9300-6986
authors.initials: AB
authors.lastname: Sendova-Franks
authors.affiliation: School of Biological Sciences , University of Bristol, Life Sciences Building , 24 Tyndall Avenue, Bristol BS8 1TQ, UK.
authors.forename: Nigel R
authors.identifier: 0000-0001-8139-9604
authors.initials: NR
authors.lastname: Franks
keywords: complex social systems; division of labour; intermittent top-down causality; motor planning; movement; self-similarity