levels. Participants with lower working memory capacity perform worse on comprehension-based tests. When investigating how mind-wandering affects retention of information, experiments are conducted where participants are asked a variety of questions about factual information, or deducible information while reading a detective novel. Participants are also asked about the state of their mind before the questions are asked. Throughout the reading itself, the author provides important cues to identify the villain, known as inference critical episodes (ICEs). The questions are asked randomly and before critical episodes are reached. It was found that episodes of mind-wandering, especially early on in the text led to decreased identification of the villain and worse results on both factual and deducible questions. Therefore, when mind-wandering occurs during reading, the text is not processed well enough to remember key information about the story. Furthermore, both the timing and the frequency of mind-wandering helps determine how much information is retained from the narrative. Reading comprehension Reading comprehension must also be investigated in terms of text difficulty. To assess this, researchers provide an easy and hard version of a reading task. During this task, participants are interrupted and asked whether their thoughts at the time of interruption had been related or unrelated to the task. What is found is that mind-wandering has a negative effect on text comprehension in more difficult readings. This supports the executive-resource hypothesis which describes that both task related and task-unrelated thoughts (TUT) compete for executive function resources. Therefore, when the primary task is difficult, little resources are available for mind-wandering, whereas when the task is simple, the possibility for mind-wandering is abundant because it takes little executive control to focus on simple tasks. However, mind-wandering tends to occur more frequently in harder readings as opposed to easier readings. Therefore, it is possible that similar to retention, mind-wandering increases when readers have difficulty constructing a model of the story. Happiness As part of his doctoral research at Harvard University, Matthew Killingsworth used an iPhone app that captured a user's feelings in real time. The tool alerts the user at random times and asks: "How are you feeling right now?" and "What are you doing right now?" Killingsworth and Gilbert's analysis suggested that mind-wandering was much more typical in daily activities than in laboratory settings. They also describe that people were less happy when their minds were wandering than when they were otherwise occupied. This effect