A research methodology is presented that combines empirical observation and experimental assessment with a view to gaining knowledge on human cognitive strategies during face-to-face interaction and evaluating the elicited strategies in the context of human-computer interaction. How this approach can be implemented effectively is illustrated by a brief summary of its application to the design and ergonomic evaluation of a simulated contextual online help system implementing human experts' help strategies. || Une méthode de recherche combinant observation et expérimentation (évaluation) est présentée. Elle permet d'acquérir des connaissances sur les stratégies cognitives humaines utilisées dans des situations de communication face à face, d'appliquer les conna