Tham khảo tài liệu 'advances in sound localization part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Auditory Guided Arm and Whole Body Movements in Young Infants 307 Fig. 8. Illustration of the three different starting positions of the infant top and the five different starting positions of the mother bottom within the rotation circle. The baby was placed on its stomach with its feet pointing towards the centre of the circle. continuous auditory stimulation to her baby. To ensure the task remained challenging for the infant there were three starting positions for the infant and five starting positions for the mother. The coordinate system was constructed with five different angles between the infant s positions and the mother s positions 90 135 and 180 . Out of a possible 15 combinations a total of 10 trials were presented in a fixed-random order four different directional trials where the shortest way would be to rotate to the left and four different directional trials where the shortest way would be to rotate to the right and two non-directional trials at 180 . A magnetic tracker system was used to measure the infant s rotations. The system consists of sensors weighing 25 g each and a magnetic box which transmits a magnetic field of 3 x 3 x 3 m. The sensors were placed on the infant in the magnetic field see Figure 9 and their positions in x y and z direction and angular rotation azimuth role and elevation were continuously recorded at 100 Hz. Fig. 9. A 7-month-old infant wearing a special body and hat placed prone in the rotation circle and participating in the experiment. The magnetic trackers to measure the infant s rotation movements were placed on the head between the shoulder blades and on the lower back. 308 Advances in Sound Localization Before each trial the experimenter placed the infant in one of the three starting positions in the middle of the rotation circle with the feet to the centre. The experimenter sat in front of the infant and maintained its attention while the mother was instructed to position herself quietly and unseen by the
