Which language learning platform first introduced the 'adaptive difficulty algorithm' in its marketing, promising personalized learning based on linguistic processing patterns?

In the world of language learning apps and platforms, product marketing has evolved dramatically in recent years. Companies now use sophisticated linguistic research to shape their branding, advertising, and user experience. This poll tests your knowledge about a groundbreaking marketing campaign that changed how language learning products are advertised and perceived by consumers. Can you identify the innovative approach that transformed the industry?

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Duolingo's 'Language DNA' campaign (2019)
Babbel's 'Cognitive Mapping' technology (2018)
Rosetta Stone's 'Dynamic Immersion' methodology (2007)
Memrise's 'Neural Learning' system (2016)