E van Muijden et al. (2012) studies the impact of playing video games as a means of brain training in late adulthood. Consider the following excerpt from the article: The prevalence of age-related cognitive decline will increase due to graying of the global population. The goal of the present study was to test whether playing online cognitive training games can improve cognitive control (CC) in healthy older adults. Fifty-four older adults (age 60-77) played five different cognitive training games online for 30 min a day over a period of seven weeks (game group). Another group of 20 older adults (age 61-73) instead answered quiz questions about documentaries online (documentary group) (van Muijden et al., 2012, Abstract). Reference van Muijden, J., Band, G. P. H., & Hommel, B. (2012). Online games training aging brains: Limited transfer to cognitive control functions. Frontiers in Human Neuroscience, 6, Article 221. https://doi.org/10.3389/fnhum.2012.00221 Using the information above, what type of study do you think this study reflects? case study O naturalistic observation O survey experiment