The most needed asset in the ever-competitive 21st century and beyond is an extraordinarily enhanced intelligence and unlimited memory. Cognitive science application to real-world learning is undergoing new unquenchable technological fire. Results of investigations that online brain training can improve fluid intelligence in healthy individuals is debated fiercely by neuroscientists, psychologists, geneticists, dietitians, ICT specialists, researchers and experts in various works of life. Theories that underlie brain features and intelligence are critically re-examined with a view to better understand the phenomena of behavioural training and the diverse electrical stimulations that are being proposed as a function of the radically changing world of information and communication technology. The current experiment investigated the effect of Lumosity training schedule on fluid intelligence, measured with Culture Fair Intelligence Test. In all, 60 Lumosity brain enrichment games, covering seven skills (attention, memory, problem solving, flexibility, processing speed, math and language), served as experimental intervention conditions. The experiment lasted for 60 days with 150 healthy 15-year old students randomized into 4 experimental and 1 control groups. Surprisingly, results showed a significant effect of Lumosity training schedule on fluid intelligence [F(4, 144) =3.1777, p< .05, partial ?2 = .081], a reflection of difference between the groups that received 12 minutes and 24 minutes daily Lumosity training in favour of the former. Results of the 9 other pairwise multiple comparisons showed lack of significant effect of the online Lumosity brain training schedule on fluid intelligence. Fluid intelligence in the main, remained stable in corroboration of the Fluid (gf) and Crystallized (gc) Theory of Intelligence that unlike the gc which is environmentally determinable (reported in another study), the gf becomes stable or flattens out from age 15, is genetically dependent and is the generalmental ability for abstract thinking, novel problems solving, and learning of new things.