They are invisible, ubiquitous and indispensable for the development of artificial intelligence (AI): ‘ghost workers’. Millions of people worldwide annotate, check and translate texts and images so that AI can understand and process the information. Who are these people and what drives them? What about their well-being? And what impact do their poor working conditions have on the development of AI? To learn more about this, I sat down with researcher Claartje ter Hoeven of Utrecht University for The Gig Work Podcast from the WageIndicator Foundation.