Synesthesia is a neurological phenomenon in which stimulation of one sensory pathway leads to automatic, involuntary experiences in a second, seemingly unrelated pathway. A person with synesthesia might perceive specific numbers as having distinct colours, or hear a particular musical note and simultaneously taste a specific flavour. Although synesthesia was first documented scientifically in the late 19th century, it was largely dismissed by researchers for much of the 20th century due to a lack of objective methods for verifying subjective sensory experiences. Renewed scientific interest emerged in the 1980s and 1990s, driven partly by advances in brain imaging technology that allowed researchers to observe unusual patterns of neural activity in synesthetes. One leading theory suggests that synesthesia results from atypical connections between brain regions that are normally kept relatively separate, possibly due to incomplete pruning of neural pathways during early childhood development. Studies estimate that synesthesia affects somewhere between two and four percent of the general population, though the exact figure remains difficult to pin down since many synesthetes are unaware their perceptual experience differs from that of others, having simply assumed everyone perceives the world the same way. Interestingly, synesthesia appears to run in families, suggesting a genetic component, though no single gene has been conclusively identified as responsible.