Theory: Greater time spent reading causes increased spelling ability. Method: Participants were currently enrolled in Year 2 of a South Australian primary school. They were randomly assigned to either the 2-hour or half-hour groups. Before lunch that day, participants spent time reading from a selection of readers that had not been used in class. Students in the 2-hour group spent a minimum of 105 and a maximum of 120 minutes reading. Students in the half-hour group spent a minimum of 20 and a maximum of 30 minutes reading. They spent the remaining time (i.e., 1.5 hours) watching videos or hearing readings of the stories in the readers (none of which involved the visual presentation of the target words). After lunch, all participants completed a spelling test on a set of 40 target words that were contained within the readers. The score on the test was calculated as the number of words spelled correctly. what is the causal construct