Guest Editorial Best of ACII 2021.

The 9TH AAAC Conference on Affective Computing and Intelligent Interaction 2021 was held in a virtual format in the fall of 2021. It was technically co-sponsored by the IEEE Computer Society and featured the recent work on Affective Computing. The six best papers from this conference were selected by the technical program chairs. They were invited to submit their extended version to be considered for this special section at the IEEE Transactions on Affective Computing. Each submission was reviewed by at least three expert reviewers and was evaluated in terms of overall contribution and the adequacy of the additional content to warrant a new article. This special section features five accepted submissions whose major contributions are summarized below. [ABSTRACT FROM AUTHOR]