We like to believe our decisions are rational, carefully weighed judgments made by our conscious minds. Yet beneath the surface of our awareness flow powerful undercurrents—biological, psychological, and environmental forces that subtly influence every choice we make, from what we eat for breakfast to who we fall in love with. Our biology sets the first invisible current. Hormones like cortisol and oxytocin alter our risk tolerance and social preferences without our knowledge. Circadian rhythms affect whether we make cautious or impulsive decisions at different times of day. Even gut bacteria appear to influence our moods and cravings through the vagus nerve, creating what scientists call “second brain” effects that operate…