The Paradox of Human Behaviour and Its Effect on Our Health

“Video meliora proboque, deteriora sequor.” Two thousand years ago, the Roman poet Ovid wrote those words for a woman about to make a decision she knew was wrong: I see the better path and approve it, yet I follow the worse. He could have been writing about public health.

Few things are as revealing in public health as the gap between what people know and what people do. We know that sleep matters, that movement protects health, that condoms reduce HIV and STI transmission, that screening can save lives, and that taking treatment as prescribed matters. Yet knowledge does not reliably translate into action. The paradox is not that people do not care about their health. It is that human behaviour is rarely governed by information alone.

After years of working across HIV, SRHR, gender and health systems, I have become increasingly wary of the idea that the right message will produce the right behaviour. People make decisions within a particular moment, a particular relationship and a particular environment. Emotions, habits, social expectations, convenience, trust, fear, money, power and past experience can all outweigh what someone knows to be medically advisable.

We are also wired for the present. The immediate reward of comfort, relief or belonging can feel more compelling than a benefit that may arrive months or years later. Add the influence of social norms — what people see others doing, what feels acceptable, what is considered normal — and the apparently irrational choice begins to look quite rational within its context. Aristotle's idea, as it is often put: we are what we repeatedly do. Health, like character, is built by habit, not by a single act of willpower.

The environments in which we live can deepen the contradiction. Unhealthy food can be cheaper and easier to access. Work can make prolonged sitting unavoidable. Digital platforms are designed to capture attention. Health services may be technically available yet difficult to reach, navigate or trust. For many women and marginalised communities, structural inequalities further narrow the choices that are realistically available.

“The question is not why people make unhealthy choices. The more useful question is: what makes the healthier choice harder to make?”

This is why I believe the most useful question in social and behaviour change is not, “Why don't people make the right choice?” It is, “What makes the healthier choice difficult, unattractive, unsafe or unrealistic in the first place?” That shift changes how we design interventions.

Good SBC is not about persuading people harder. It is about understanding behaviour well enough to design for it. Communication matters, but so do service design, policy, community norms, incentives, physical environments and the small frictions that stand between intention and action. Homer's Ulysses knew he could not out-argue the pull of the Sirens' song, so he did not try. He had his crew tie him to the mast before the temptation arrived. He changed the conditions, not his willpower. That is what good behaviour-change design does — it does not ask people to resist; it removes the need to.

The paradox of human behaviour should therefore not make us cynical about public health. It should make us more precise. People are neither perfectly rational nor simply uninformed. They are responding to the world as they experience it. If we want healthier societies, we have to work with that reality — designing systems in which the healthier, safer and more equitable choice is also the easier choice.

“People do not always act on what they know. They act within the realities of their lives.”