The comparison everyone avoided now sits on the table, and it changes the tone. A meticulous review of school cohorts tracks cognitive gains, dips, and gaps across decades, so patterns finally come into focus. The famous rise exists; the slowdown is real. Yet the reversal unsettles. The term IQ still anchors the debate, while context, education, environment, and habits, shapes the story. Numbers matter here, although causes pull in different directions, and consequences touch families, classrooms, and policy.
From the Flynn effect to a stalled rise
For years, researchers described the “Flynn effect,” a steady climb in reasoning scores across many countries. From 1950 to 1990, the trend increased by the extraordinary rate of three points per decade for standardized measures, a striking rate for standardized measures. In addition, there was research from France in later years that backed that trend.
In French schools, a 1967 cohort compared with 1982 pupils showed clear improvement, strongest among those who continued their studies. The signal looked robust, though gains rarely spread evenly across groups. Even then, some profiles advanced faster than others, while a minority stayed flat.
Researchers tracked IQ scores going up, yet they also saw limits. Gains softened as time moved on, which hinted at ceilings or shifting conditions. The rise slowed, then plateaued. The story sounded less linear once context, schooling models, home inputs, and social change, entered the frame.
IQ trends flip: what the new comparisons show
Around the 2000s, comparisons started to point in the other direction. A psychomotor therapist who expected ongoing progress instead found a clear decline. In France, the average IQ moved from 102 in 1990 to 98 in 2016, a four-point drop over twenty-six years, larger than the 1967–1982 gain.
Norway supplied unusually strong evidence. An analysis of 740,000 conscripts showed a fall from 102.3 in 1975 to 99.4 in 1991. That sample size reduced doubt and highlighted cohort effects. Denmark and the United Kingdom revealed similar slopes, so the pattern no longer looked like a local quirk.
The French fall shook people because median values moved, and dispersion shifted too. According to neuropsychologist Marc Lefranc, the shock touched the average and the spread, with some profiles dropping sharply. That meant parts of the distribution lost ground, while others held steady, complicating easy explanations.
Where causes stack up: school, environment, and habits
Genes aren’t able to change that quickly, so the environment is suspect. Endocrine disruptors are frequently at the top of the list, because they can affect thyroid functioning during early neurodevelopment. It’s difficult to avoid them since they may be present in air, water, and food, which only heightens the stakes related to regulation and household purchases.
Education, while more democratic, also changed its standards. Critics contend that requirements occasionally relaxed as access expanded. According to reports, the average IQ score that was previously associated with the baccalauréate, which was estimated to be 100, has decreased to 88 for generations born after 1995. That claim suggests a dilution effect within credentials.
Screens also reshape how minds learn. Time spent scrolling compresses attention and reduces deep reading. Spoken dialogue suffers, yet dialogue builds vocabulary and working memory. Families feel the pull of convenience because devices calm children, however the tradeoff can be steep for long-term learning and IQ outcomes.
Beyond averages: what IQ dispersion reveals
Averages tell only part of the story; spreads tell the rest. When variance widens, classrooms face mixed needs, so teaching becomes harder. Teachers juggle advanced and struggling learners, while the middle shrinks. That makes generic lesson plans weaker, and targeted supports more urgent.
Dispersion raises policy stakes. If some profiles “plummet,” as Lefranc warns, then early screening matters. Vision, hearing, sleep, and language environments need quick fixes. Modest gains compound when they arrive early, and they often cost less than late interventions. Small changes stack, while delays become expensive.
Researchers also watch cohort timing. Economic stress, curriculum shifts, or technology waves hit ages differently. A new policy can benefit one cohort and miss the next. Because these shocks overlap, the same average in two years can mask different distributions. Public debate, therefore, should include dispersion and IQ together.
Practical responses that protect cognitive potential
Families control several high-leverage habits. Read aloud daily, even brief sessions. Encourage open talk during meals, since conversation grows verbal reasoning. Keep screens out of bedrooms and set device “off ramps” before sleep. Short routines add up, which supports memory, attention, and IQ-related performance across school years.
Schools can act without waiting for perfect consensus. Restore practice in reading comprehension, numeracy, and spatial skills. Use cumulative reviews so knowledge sticks, and space retrieval instead of cramming. Form small groups for targeted help. When administrators track variance, not just means, they allocate time more wisely.
Policy makers can reduce exposure where risks cluster. Tighten standards for endocrine disruptors, improve food labeling, and fund early-childhood checks. Support evidence-based teacher training and family literacy. Because causes overlap, the best answer weaves regulation, school craft, and home routines into one plan built for IQ resilience.
Why this generational comparison now matters for almost everyone
Trends can change again, and that possibility should energize us. The debate keeps its edge because numbers speak, while choices still matter. Families, teachers, and leaders share the levers. When habits shift and standards sharpen, IQ scores can stabilize, and wider skills can grow, which leaves room for better futures.