A while ago, I was shopping with my mother at a large retail store in Lahore. After filling our cart, we reached the checkout counter. Just ahead of us, a customer who had already finished paying suddenly confronted the cashier about a mismatch between the items he bought and what appeared on his receipt.
This immediately put my mother and me on high alert. Knowing someone right before us had encountered a problem, we carefully cross-checked every item in our cart against the receipt the cashier generated before taking our payment. We probably wouldn’t have been nearly so thorough or slow if we hadn’t witnessed that earlier complaint.
Later, I realized something important: if we hadn’t picked up on the previous customer’s frustration and suspicion, we would have paid quickly and instinctively without double-checking anything. That small episode revealed two things. First, emotions—especially uneasy ones—are highly contagious. Second, we humans have a strong tendency to latch onto negativity.
And that tendency isn’t a flaw; it’s a feature. Even though most of us no longer live on the African savanna dodging predators, our brains are still wired by evolution to treat negative signals as urgent warnings. In modern life, that ancient mechanism still serves a purpose: it helps us spot potential mistakes, losses, or dangers—whether it’s an overcharge at a store or something far more serious. Negative emotions remain one of our built-in alarm systems.