Study title

United Kingdom

Group

Individual

ParticipantsParticipants were recruited on campus at the University of Stirling, and from two local secondary schools. For the paper planes study, ten chains of ten participants took part. Their mean age was 20 years (SD=6.02, youngest=13, eldest=48), and the ratio of males to females was approximately 50:50 (53 males, 47 females). Ten chains of ten participants also took part in the spaghetti towers study. Their mean age was 21 years (SD=7.14, youngest=11, eldest=47), and the ratio of males to females was approximately 40:60 (39 males, 61 females). As the participants for both studies were drawn from the same pool of participants (predominantly undergraduates from the University of Stirling) it is possible that some individuals took part in both parts. We did not consider it necessary to exclude individuals from participating in one study if they had already taken part in the other.MaterialsPaper plane builders were provided with a single sheet of A4 paper, and spaghetti tower builders were provided with a standard 500g packet of spaghetti and 78g of modelling clay (Early Learning Centre 'Modelling Material').ProcedureParticipants were randomly assigned to the positions 1 to 10 in each chain. The participants were informed that they were about to take part in a team challenge, and that they would be called in turn to engage in the task. In order to simulate generational succession, the participants' start times were staggered, such that every two and a half minutes a new person entered the group (see Table 1 for information on group composition at any given time). While they were in the test group, each participant had five minutes of observation time, during which they could watch the previous participants building their artefact, followed by five minutes of building time, during which they had to construct their own artefact. Once their time was up, they left the test group. The staggered start and finish times had the effect that, at any given time (except at the very start and very end of any given chain) there were four individuals together in the group, two of whom were observing, and two of whom were actually engaged in the task (see Table 1). So, for example, a chain would begin with participant 1 building their artefact, with participants 2 and 3 observing. Then, two and a half minutes in, participant 2 would also start building, and participant 4 would join the group as an observer. The aim was to simulate a miniaturised society, in which one generation would have the opportunity to interact with and observe individuals from the previous two generations, but not those further back. However, we did retain all artefacts for inspection by later participants, to reflect the more permanent record generated by material culture.While they waited their turn to join the group in the test area, participants sat together in an adjoining area from which the test area could not be seen. When participants joined the group in the testing area they were provided with written instructions about the nature of the task. They were informed of the aim of the task (i.e. to build a paper aeroplane that flew as far as they could make it go, or to build a spaghetti tower that was as high as they could build it) and of their time restrictions (five minutes of observation time followed by five minutes in which to build their own artefact). They were also informed that they were permitted to communicate with other members of the group regarding the task, and that they were allowed to observe and learn from others. Within the test group, participants were kept aware of their current role (observing, constructing), and the time elapsed, by a computer display and reminders from the experimenter. Once an individual's five minute construction period was up, their artefact was evaluated. For spaghetti towers, this involved the experimenter measuring the height of the tower after it had been standing for 30s. For paper aeroplanes, this involved the participant throwing their plane three times, with the experimenter recording the distances flown, and then taking the best of the three measurements (to allow for mis-throws). This would generally take less than 30s, so feedback to the group was fairly rapid, and it was possible for later participants to revise their designs on the basis of this feedback. The artefacts were then retained for display, for later members of the group to inspect, and the experimenter wrote down the measurements next to each, so that this information was also available. Participants left the testing area once their artefact had been evaluated.For further information see Caldwell & Millen (2008) Evol Hum Behav 29, 165-171.