The tasks were conducted on a laptop computer using E-Prime software version 2.0 to control the stimulus presentation and to specify the correct responses. The letters were displayed on LED-backlit HD antiglare screen with 1024 × 768 pixel resolution and refresh rate of 60 Hz. A chin rest was used to fix the distance of 50 cm between the screen and participant's eye. A response box was used to record reaction times and correct responses. The box was positioned halfway between the chin rest and the screen to enable easy reach.