Before revision: Afterwards, when the concerned person stared at a truck for a while the truck seemed to decompose into its motor, chassis, driver cab and the person could only focus on one of these parts until he shortly closed his eyes or looked away which reset the shape to the complete truck again.
After revision: Afterwards, when the subject stared at a truck for a while the truck seemed to decompose into its motor, chassis, driver cab and the person could only focus on one of these parts until he briefly closed his eyes or looked away which reset the shape to the complete truck again.