2012 Toyota Prius Owners Manual - Page 563

2-3. Operating the lights and windshield wipers Increases the intermittent windshield wiper frequency (if equipped) Decreases the intermittent windshield wiper frequency (if equipped) Washer/wiper dual operation The wipers will automatically operate a couple of times after the washer squirts. If the headlights are on, the headlight cleaner will operate once.