The two players can also play online while using split screen. This game mode is normally exclusive to the Xbox 360 version of Left 4 Dead and Left 4 Dead 2, but may be accessed in the PC versions if you have a controller for the second player and modify some files.
Serial memory processing - Wikipedia. Serial memory processing is the act of attending to and processing one item at a time. This is usually contrasted against parallel memory processing, which is the act of attending to and processing all items simultaneously. https://en.wikipedia.org/wiki/Serial_memory_processing
Sensory processing (originally called sensory integration dysfunction or SID) refers to the way the nervous system receives messages from the senses and turns them into appropriate motor and behavioral responses.