  Modern search engine result pages often provide immediate value to users and
organize information in such a way that it is easy to navigate. The core
ranking function contributes to this and so do result snippets, smart
organization of result blocks and extensive use of one-box answers or side
panels. While they are useful to the user and help search engines to stand out,
such features present two big challenges for evaluation. First, the presence of
such elements on a search engine result page (SERP) may lead to the absence of
clicks, which is, however, not related to dissatisfaction, so-called "good
abandonments." Second, the non-linear layout and visual difference of SERP
items may lead to non-trivial patterns of user attention, which is not captured
by existing evaluation metrics.
  In this paper we propose a model of user behavior on a SERP that jointly
captures click behavior, user attention and satisfaction, the CAS model, and
demonstrate that it gives more accurate predictions of user actions and
self-reported satisfaction than existing models based on clicks alone. We use
the CAS model to build a novel evaluation metric that can be applied to
non-linear SERP layouts and that can account for the utility that users obtain
directly on a SERP. We demonstrate that this metric shows better agreement with
user-reported satisfaction than conventional evaluation metrics.
