But there is no conscious thought, because there is no time for it.The second type of thinking is the domain of logic, deliberation, reasoned discussion, and scientific method.
Research suggests that individuals born earlier to the cut-off date are more likely to play professionally, earn higher wages if they do and perform better.
Cut-off dates for academic cohort structuring, including the setting of academic years, are usually determined by national education authorities and tend to be based on autumn start dates, so August or September cut-off dates are common in the Northern Hemisphere and February or March cut-off dates are common in the Southern Hemisphere.
The expected distribution of births in any given month across a population correlates closely to the number of days in the month, with February as the shortest month having the fewest births.
The first graph shows the distribution of births, by month, for the European Union over the ten years from 2000 to 2009.
There is a slight but clearly perceptible increase in the birth rate in the summer months.
A ‘relative age effect’ is illustrated in the second graph by the month of birth distribution of over 4,000 youth players involved in the qualifying squads for U17, U19 and U21 tournaments organised by UEFA in 2010/11.
This tendency reflects the historical need for children to be involved in summer-time agricultural work with school starting after harvesting.
A ‘relative age effect’ in academia is illustrated in the third graph which shows the % deviation from month of birth profile norms evident in graduations from Oxford University over a 10-year period.
The difference in maturity - which can be extreme at young ages: a six-year old born in January is almost 17% older than a six-year old born in December in the same year - causes a performance gap that persists over time.
The term month of birth bias is also used to describe the effect and season of birth bias is used to describe similar effects driven by different hypothesised mechanisms.
The authors find that "the youngest members of each cohort score 4–12 percentiles lower than the oldest members in grade four and 2–9 percentiles lower in grade eight...