Page 160 - Demo

Chapter 7158MethodSubjects and housing Our sample included four adult Bornean orang-utans (Pongo pygmaeus; females: Samboja, Sandy, Wattana; male: Amos) that lived in a fission-fusion enclosure with four other orang-utans (one of which was transferred during the study period; Table 1) in Apenheul Primate Park (Apeldoorn, The Netherlands). The females, but not the male, had prior experience with touchscreen-based research. However, none of the individuals had experience with eye tracking.The orang-utans were housed in a building consisting of four indoor enclosures that were each connected to outdoor islands. The orang-utans were typically housed in 3-4 subgroups and group composition was sometimes changed with the aim of mimicking the natural social structure of orang-utans, in which they form temporary parties but no stable social groups. Some individuals never shared enclosures to avoid conflict (e.g., two adult males). The test setup was located in one of their night enclosures, out of view of the public. The setup was accessible from two of the indoor enclosures. Testing took place between March and August 2022 on Tuesdays and Fridays between 11.00 and 13.00. Table 1. Overview of the Apenheul orang-utans.Name Sex Date of birth Origin Participating? Calibration accuracy (precision)Kevin M ~1982 Wild NoSandy F 29-4-1982 Captive Yes 2.1mm (2.3mm)Wattana F 17-11-1995 Captive Yes 0.5mm (2.3mm)Amos M 20-12-2000 Captive Yes 0.4mm (5.0mm)Samboja F 9-6-2005 Captive Yes 0.1mm (1.3mm)Kawan (until 20-6-2022) M 22-2-2010 Captive NoBaju M 2-12-2015 Captive NoIndah F 19-10-2017 Captive NoExperiment 1ProcedureParticipants were calibrated and tested using Tobii Pro Lab v. 1.194 and a Tobii Pro Spectrum with a sampling frequency of 1200Hz that was attached to a 24” monitor (16:9, 1920x1080). The monitor was placed behind a 1.2 cm thick polycarbonate panel with a drinking nozzle. Throughout calibration and testing, Tom Roth.indd 158 08-01-2024 10:41