The present paper studies how, in deictic expressions, the temporal interdependency of speech and gesture is realized in the course of motor planning and execution. Two theoretical positions were compared. On the "interactive" view the temporal parameters of speech and gesture are claimed to be the result of feedback between the two systems throughout the phases of motor planning and execution. The alternative "ballistic" view, however, predicts that the two systems are independent during the phase of motor execution, the temporal parameters having been preestablished in the planning phase. In four experiments subjects were requested to indicate which of an array of referent lights was momentarily illuminated. This was done by pointing to the light and/or by using a deictic expression (this/that light). The temporal and spatial course of the pointing movement was automatically registered by means of a Selspot opto-electronic system. By analyzing the moments of gesture initiation and apex, and relating them to the moments of speech onset, it was possible to show that, for deictic expressions, the ballistic view is very nearly correct . 0 1985 Academic Press, IncThe general issue addressed in this article concerns the synchronization of speech and gesture. More specifically the aim is to investigate how the frequently noted interdependence of speech and gesture is realized in the course of motor planning and execution. Do the two systems operate interactively, in the sense that mutual adaptation takes place during the phase of motor execution, or do they rather operate in a ballistic or independent fashion in so far as

Prey animals have evolved a wide variety of behaviours to combat the threat of predation, and these have been generally well studied. However, one of the most common and taxonomically widespread antipredator behaviours of all has, remarkably, received almost no experimental attention: so-called 'protean' behaviour. This is behaviour that is sufficiently unpredictable to prevent a predator anticipating in detail the future position or actions of its prey. In this study, we used human 'predators' participating in 3D virtual reality simulations to test how protean (i.e. unpredictable) variation in prey movement affects participants' ability to visually target them as they move (a key determinant of successful predation). We found that targeting accuracy was significantly predicted by prey movement path complexity, although, surprisingly, there was little evidence that high levels of unpredictability in the underlying movement rules equated directly to decreased predator performance. Instead, the specific movement rules differed in how they impacted on targeting accuracy, with the efficacy of protean variation in one element depending on the values of the remaining elements. These findings provide important insights into the understudied phenomenon of protean antipredator behaviour, which are directly applicable to predator-prey dynamics within a broad range of taxa.

Gamification is widely applied to increase user engagement and motivation, but empirical studies on effectiveness are inconclusive, and often limited to the integration of tangible elements such as leaderboards or badges. In this paper, we report findings from a study with 36 participants that uses the lens of Self-Determination Theory to compare traditional gamification elements, and the concept of juiciness (the provision of abundant audiovisual feedback) in the VR simulation Predator!. Results show that gamification and juiciness improve user experience, but that only juiciness fulfills all basic psychological needs that facilitate intrinsic motivation when applied in nongaming settings. User preferences favour the combination of both approaches, however, neither improved performance, and there is evidence of juicy elements influencing user behaviour. We discuss implications of these findings for the integration of gamification, reflect on the role of both approaches in the context of feedback, and outline challenges and opportunities for further research.

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