At Erik's house, the shower water gets very hot when someone flushes the toilet. Erik has learned to jump out of the shower water as soon as he hears a toilet flush. When Erik goes to college, he learns that flushing the toilet in his dorm has no impact on the temperature of the shower. After Erik comes home for the break, he doesn't automatically jump out of the shower when he hears the toilet flush, which is best explained by ______.