Page 136 - Emotions through the eyes of our closest living relatives- Exploring attentional and behavioral mechanisms

Chapter 6
testing. The screen was always directed at one of the four enclosures, which prevented orangutans in the other enclosures from seeing the videos. Food was provided four to six times a day and consisted of a variety of vegetables, and sometimes nuts, hay, and fruit, hidden in the enclosure for foraging purposes. Water was available ad libitum.
The care and housing of the orangutans was adherent to the guidelines of the EAZA Ex situ Program (EEP). As the study was non-invasive in nature, there was no need for the approval of the Ethics Committee of Apenheul primate park and the study complied with the requirements of the Dutch Animal Care and Use Committee.
Stimuli
The experiment involved three categories of mute, full-screen videos, each consisting of both a yawn and control condition (see Figure 2 for examples). We used mute videos as the enclosures were sealed with thick glass that dampened most of the sound both ways. Yawn videos showed clear yawns either filmed from the front or side, whereas control videos consisted of individuals with a neutral face and in a relaxed body position. Both types of videos involved movement, with yawn videos showing a wide gaping of the mouth followed by a relaxation of the mouth and jaw (Barbizet, 1958), including display of the teeth, and control videos showing an individual with a closed mouth with random movements of the lips. Both control and yawn videos were always of the same individual, and therefore the body position and face were identical.
The familiar video category consisted of two adult males housed in the zoo. For the unfamiliar video category, we used two adult males taken from clips on YouTube. Finally, in the avatar video category we used two mirrored videos of a computer- generated adult male. The 3D orangutan was created by Paul Kolbrink from XYZ- Animation and designed in Autodesk 3ds Max (2017) using the Octane render engine. Using these videos, we created video sequences starting with a primer video that depicted caretakers beckoning the orangutans towards the TV screen, which were created to grab the orangutans’ attention right before the start of a trial. As we repeated the presentation of our video database four times during the course of the experiment, there were four different primers; one for every repetition.
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