The phrase names a real and slightly uneasy feeling, that the ground of what counts as normal has quietly moved under our feet. The obvious way to explore it is to start listing examples, but a list tends to slide quickly into either nostalgia or grievance, and it takes for granted the very thing worth examining: our sense of normal itself. It turns out that this sense is not a fixed reference point at all. It is a constantly re-anchoring one, and two lines of research show it drifting in ways we cannot detect from the inside. Once you see how the drift works, the interesting question stops being which things are no longer normal, and becomes how we would ever know.
The baseline moves between generations
The first mechanism was named by the fisheries scientist Daniel Pauly, who noticed that each new generation of scientists took the ocean of their own youth as the natural baseline, and measured decline only from there. The condition, since studied more widely as shifting baseline syndrome, was given fuller empirical form by the ecologist Sonia Papworth and colleagues in a 2009 paper in Conservation Letters. They distinguished two versions of it. In generational amnesia, younger people simply never knew the earlier state of things, so cannot register what has gone. In personal amnesia, individuals gradually forget their own past experience and revise their memories towards the present.
The result is a slow, invisible downgrading of what registers as normal. Fewer birds in the hedges, a quieter dawn chorus, a high street with different shops, a river with different fish: each generation inherits an already-altered world and files it as the natural state, measuring any further change only from that lowered mark. This is one honest answer to the phrase. A great many things we take to be normal may no longer be what they were, not because we are careless, but because we never had access to the earlier baseline against which the change would show.
The concept itself stretches to fill the range
The second mechanism is stranger, and comes from the laboratory. In a 2018 study in the journal Science, David Levari, Daniel Gilbert and their colleagues documented what they called prevalence-induced concept change. When they showed people a long series of dots and asked them to identify the blue ones, then quietly made blue dots rarer, participants began to classify purple dots as blue, as though their idea of “blue” had expanded to keep finding examples. The same happened with weightier judgments: when threatening faces grew rare, neutral faces started to look threatening; when unethical research proposals grew rare, innocuous ones started to look unethical. Most tellingly, the effect persisted even when participants were warned it would happen and paid to resist it.
The implication is that “normal” and its opposites are not fixed categories but relative ones, which stretch or contract to fill whatever range of experience we are given. A concept does not sit still while the world changes around it; it moves to keep its share of the cases. So our judgment of what is normal can shift even when the underlying reality holds perfectly still, simply because the mind rescales to the range in front of it. Normal, on this evidence, is less a fact about the world than a running average of what we have lately been shown.
Why the phrase cuts both ways
Put the two findings side by side and the uneasy feeling behind the phrase turns out to be well founded, though not quite in the way it intends. Our sense of normal is unreliable in two opposite directions at once. Because baselines drift, genuinely changed things can still feel entirely normal, and we under-detect real change. Because concepts stretch, stable or even improving things can come to feel abnormal, and we over-detect change that is not there. The phrase assumes we can tell which things have stopped being normal. The research suggests the harder and more useful lesson is humility about the reference point itself, since the ruler we are measuring with is quietly made of elastic.
That is a more interesting takeaway than any list could offer. It suggests that the things we are most confident are normal, in either direction, are exactly the ones worth looking at twice, because our confidence is precisely the feeling a moving baseline produces.
What the evidence does and does not settle
A few honest limits belong here. Shifting baseline syndrome is best developed in ecology, and its extension to social and cultural life is partly by analogy; its empirical base has grown, with a 2024 global synthesis reporting it to be widespread, but it was long constrained by how rarely we have good long-term records to check perceptions against. Prevalence-induced concept change is a robust set of experiments, but they are laboratory tasks, and how far the effect governs messy real-world norms is still being mapped. It is also worth remembering that we err in the opposite direction too, through rosy retrospection and a general declinism that paints a golden former normal which frequently never existed. And crucially, none of this tells us whether any particular change is good or bad. It speaks only to how poor an instrument our gut sense of normal is for judging that.
Within those limits, the phrase earns a better reading than the nostalgic one. It is not really an invitation to catalogue what has been lost. It is a caution about the anchor itself: normal is a moving point we mistake for solid ground, drifting between the generations and stretching to fit the range of a given life. The things we are surest about are the ones that reading should make us least sure of, which is an uncomfortable thought, and a genuinely useful one.