We created a system to send regularly-spaced, multiple-choice questions to students' own mobile devices to help secondary school students in Cameroon with exam practice via either SMS or WhatsApp. Students' participation rates were heavily impacted by trust in the intervening organization and …

Their results were surprising. With all the hype around Internet messaging services like WhatsApp, the researchers were expecting WhatsApp to well outdo old-school SMS text messages. Yet, SMS beat WhatsApp for mobile phone test prep!