## 3 Materials and Methods
### Procedure  
Each participant interacted with only one of the two versions of the application, depending on the group to which he/she had been assigned. A moderator oversaw the activities of both groups. Following a script, the moderator explained the aim of experience and the activities that the participant would carry out. The brief explanation informed participants that they should not be nervous, as they were not being examined, it also included information on the goal of the activity and explained that they were going to be asked to listen to and look at a lesson and then answer questions in a questionnaire and in an interview (the latter exclusively for the AR group). Each participant was encouraged to think aloud at all times. Script paragraph pieces are displayed:  
_\"I am [insert Monitor Name] and I will be with you throughout this activity. I'm studying computers and I like to learn how to use computers, tablets and cell phones to help people._  
_I asked you to be here today because I need your help. I'm trying to figure out how to make a reading app for kids like you. So, I want you to help me by doing an activity. It's going to take about 25 min. Don't get nervous; we are testing the application, not you. Really, you're not going to make a mistake here. There are no right answers or wrong answers but if I see that you're paying attention I'll give you a prize (I'll give every participant a prize). [...]. Now I am going to explain what we're going to do. You know how in some classes professors show you videos to teach you something? Well, we're going to show you a video and I want you to listen carefully while you watch it [...].\"_  
A sound check was performed prior to commencing the lesson to give each participant the opportunity to adjust the volume to a suitable level. In the case of the AR group, participants were given a smartphone and asked to perform a marker reading test to familiarize the participant with the Augment AR viewer app and ensure they knew how to correctly operate the device. For this test the moderator provided a demonstration and projected images in augmented reality, after which the participant was asked to replicate the actions using a different marker. Next, the participant was presented with a brief demo of the proposed lesson format. The participant had to interact with the demo and in the same fashion as they would in the actual lesson, meaning they had to project images and listen to audio snippets. Up until this point the images observed by the AR group were entirely unrelated to the lesson material. Once ready, the participant proceeded with the lesson. The theme of the lesson was the story of [PERSON], the canine crewmember who travelled on Sputnik 2. All participants listened to the same audio, an adaptation of the Spanish version of Laika the Little Astronaut Dog (Educational Video Story--Laika's Space Journey. [[https://bit.ly/2](https://bit.ly/2) tKwzdl]([https://bit.ly/2](https://bit.ly/2) tKwzdl)) by Blue Planet Tales. They also observed images relevant to the content of the lesson but in different formats. For the VIDEO group, the interface used for the lesson was a video player. The participant was responsible for pressing play to start the video. The entire lesson was delivered in a single sitting without pauses. All audio and visuals were delivered via the aforementioned video player. The visuals consisted of static and animated images (see Figure 1). In contrast, the lesson that was delivered to the AR group was split into separate parts that were presented one at a time. From the adapted material, the main ideas had been highlighted and the times when video images originally changed were taken into consideration to define the parts that would make up the AR lesson. When defining the resulting parts steps were taken to ensure they made sense when listened to (i.e., showcased complete ideas) and that they were as long as possible in order to minimize the number of interruptions to the lesson.