Which AI technique revolutionized retail recommendation systems around 2017-2018 by dramatically improving personalization and is now used by most major e-commerce platforms?

Modern e-commerce platforms employ sophisticated recommendation algorithms that significantly impact consumer behavior and sales performance. These systems have evolved dramatically in recent years, moving far beyond simple 'customers who bought this also bought' suggestions. Test your knowledge of how today's advanced retail recommendation systems actually work and the surprising ways they influence purchasing decisions.

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Transformer neural networks with self-attention mechanisms
Rule-based expert systems with decision trees
Simple collaborative filtering using Pearson correlation
Regression analysis with demographic clustering