6.2. Materials and Methods 6 99 also observed with natural sight (i.e., with deactivated phosphene simulation) during the practice session at the beginning of the experiment. Movement Control In contrast to Experiment 1, the camera pose in the virtual environments was entirely dependent on the participant’s pose in reality (the position of the headset). Due to the relatively confined experimental space for the tasks in the second experiment, there was no need for a controller-based repositioning, as participant’s could perceive the entire environment by rotating on the spot. Therefore, movement control of the character by using the trackpad on the VR game-controller was disabled, providing an even more immersive and naturalistic simulation compared to the first experiment. Subjects were instructed to stand in the middle of the room and to look around in all directions. Subjects could turn around in place, but were instructed to avoid walking away from the start position. Between trials, subjects were redirected to the start location and orientation if necessary, facing an instruction screen in the VR environment. Practice The total experiment lasted maximally two hours, starting with a practice session of roughly 30 minutes. In the practice session, the subjects could get adjusted to the VR experience, the phosphene simulation and the experimental tasks. The practice session included several trials with free exploration and several visual search trials in the studio environment. Furthermore, the subjects performed three scene recognition trials in unfamiliar example scenes. The unfamiliar environments that were used for practicing the scene recognition task were never reused in the actual scene recognition session. In addition to the practice session at the beginning of the experiment, several extra familiarizationtrials were included before each scene recognition block throughout the experiment. The data of these familiarization trials were not included in the analysis. During the familiarization trials, the participants performed a visual search task in the studio environment. This served two purposes: 1) each time when the simulation condition was switched, the subject had the opportunity to get adjusted to the new simulation condition before starting the scene recognition trial 2) by performing extra trials in the studio environment, during the scene recognition session, subjects became increasingly familiarized with the environment before the visual search session. Scene Recognition Session After the practice session, subjects performed a scene recognition session that lasted roughly one hour, including breaks. The scene recognition session consisted of three blocks, one for each condition, plus another repetition of three blocks. Each block contained three trials, each with a different environment. The instructions were to report the room category as fast as possible, while considering that accuracy is preferred over speed. To ensure that the total duration of the experiment did not exceed two hours, all scene recognition trials were limited by a maximal duration of two minutes, after which subjects were instructed to provide a (forced) choice of room category, even if they were not confident of their answer. The environments were randomly selected and the order of the experimental conditions were randomly shuffled to avoid systematic biases owing to environment characteristics, practice effects or fatigue. Before each scene recognition
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