In a study on experience‐based learning in serious games, 45 players were tested for topic comprehension by a questionnaire administered before and after playing the single‐player serious game Peacemaker (Impact Games 2007). Players were divided into two activity conditions: 20 played a 1‐h game with a 3‐min half‐time break to complete an affect self‐report form while 25 also participated in a 20‐min reflective group discussion during their half‐time break. During the discussion, they were asked by an experimenter to reflect on a set of topics related to the game. We present the analysis of the questionnaires, which illustrates that contrary to our expectations the reflection period had a negative effect on the learning of the players as judged by their performance on closed‐form questions at levels 1–5 (out of 6) on the Bloom taxonomy of learning outcomes. The questionnaire also included a few open questions which gave the players a possibility to display deep (level 6) learning. The players did not differ significantly between conditions regarding the questions measuring deep learning.