““Users pass through the Investment Phase of the Hook Model each time they send a selfie, doodle, or goofy photo. Each photo or video sent contains an implicit prompt to respond and the Snapchat interface makes returning a pic incredibly easy by double tapping the original message to reply. The self-destruct feature encourages timely responses, leading to a back-and-forth relay that keeps people hooked into the service by loading the next trigger with each message sent.””
