Page 135 - Demo

Absence of cognitive bias to flanges in orang-utans1336et al., 2022), but only two of the orang-utans from that previous study (Sandy & Samboja) eventually participated in this study. With regard to participation in the experiments described here, three individuals participated in the dot-probe experiments (both flange size and symmetry version), while six individuals participated in the preference test. Table 1 indicated which individuals participated in the experiments.Table 1 – Orang-utans housed in Apenheul at the time of study.Name Sex Date of birth Origin Dot-probe Preference testKevin M ~1982 WildSandy F 29-4-1982 Captive Yes YesWattana F 17-11-1995 Captive YesAmos M 20-12-2000 CaptiveSamboja F 9-6-2005 Captive Yes YesKawan M 22-2-2010 Captive Yes YesBaju M 2-12-2015 Captive YesIndah F 19-10-2017 Captive YesApparatusTouchscreen experiments were conducted via E-Prime 2.0 on a TFT-19-OF1 Infrared touchscreen (19”, 1280 x 1024 pixels). The touchscreen setup was encased in a custom-made setup which was incorporated in one of the orangutans’ night enclosures. This night enclosure could be made accessible from two of the main enclosures by the animal caretakers. The researchers controlled the sessions on a desktop computer connected to the touchscreen setup and could keep track of the orangutans’ responses on the touchscreen through a monitor that duplicated the touchscreen view. Additionally, the researchers had access to a livestream with a camera that was built in the enclosure, allowing them to observe the participant. Correct responses were rewarded with a sunflower seed on a 100% fixed reinforcement ratio. For most individuals, the rewards were delivered by a custom-built autofeeder linked to the desktop computer, that dropped a reward in a PVC chute. However, Kawan and Baju did not habituate properly to the presence of the feeder, and kept trying to push it over with sticks. Therefore, we decided to reward them manually. The researcher was positioned behind the setup which prevented visual contact between the orangutans and researchers.Tom Roth.indd 133 08-01-2024 10:41