For over a century, intelligence metrics appeared to rise steadily across generations, a phenomenon widely known as theFlynn Effect. Recent declines in international academic performance, particularly those reported in PISA 2022, have renewed debateover whether this historical trend has reversed and whether Generation Z is experiencing genuine cognitive decline. This studyevaluates competing explanations: a biological decline hypothesis and an environmental performance-impairment hypothesis. Usingan integrative theoretical approach, the analysis synthesizes psychometric intelligence research, international assessment data,cognitive load theory, executive function studies, dual-process models, cognitive offloading research, and psychosocial frameworksaddressing anxiety and self-efficacy. While academic performance has declined structurally across several OECD countries, evidencefor widespread biological regression remains inconclusive. Convergent findings instead suggest that digital multitasking, increasedextraneous cognitive load, diminished deep reading engagement, reliance on external memory systems, and heightened psychosocialstress may impair sustained attention and executive functioning, thereby constraining applied academic performance withoutreducing latent intelligence. The study proposes an environmental cognitive constraint model in which intelligence remains relativelystable but its measurable expression is shaped by contemporary digital ecosystems.