A HUMBLE set of wooden shapes celebrates its 100th anniversary this year. Unit blocks, developed by early-childhood education pioneer Caroline Pratt in 1913, are wooden bricks, in carefully chosen sizes and shapes, found in classrooms in America and beyond for the past century. Ms Pratt designed her blocks while standing on the shoulders of giants, notably Friedrich Fröbel, the originator of kindergarten education, who believed in the value of play to shape behaviour and aid in children's intellectual and emotional growth. How do unit blocks help children learn? Fröbel spent the first half of the 19th century tinkering with the oddball notion that even very young children could learn scientific, artistic and natural principles simply by playing with various physical objects, which he called "gifts". This was a big departure from the idea of learning via adult-led activities or, for older children, rote memorisation. Fourth in Fröbel's series of 20 age-calibrated gifts was a set of eight blocks, sized ½ by 1 by 2 inches, or a 1:2:4 ratio, that could be formed into a cube. Fröbel's principles were widely adopted after his death in 1852, albeit in a simplified form, but the idea of using concrete objects to establish a basis for later abstract knowledge remained at the centre of this approach. One of his followers, Patty Hill, created her own set of blocks nearly 20 times larger with pegs, holes and grooves that required cooperation among children to create large constructions. (With her sister Mildred, Hill also composed the song that became "Happy Birthday to You".) She found Fröbel's blocks too small for toddlers to grasp. Pratt, a contemporary of Hill's, observed her blocks at work and charted a middle course. Her unit blocks are bigger than Fröbel's but small and lightweight enough to allow for either individual or collaborative building. The basic unit is 5½ by 2¾ by 1⅜ inches (140 by 70 by 35mm).

Educational theorists cite a laundry list of the benefits that children derive from playing with unit blocks, many of which echo Fröbel's writings. Co-operative building develops language and social skills. The "unit"-based measurements of halves, doubles and quadruples, combined with columns, ramps, curves, buttresses and other specialised shapes, lay the foundations for basic maths and geometry. Balance and collapse teach the nature of gravity. Ramps and columns can be used to make simple levers and fulcrums. The need to place blocks carefully develops hand-eye co-ordination. Does all this ascribe too much educational potential to simple chunks of wood? In fact, multiple studies over several decades back up these claims, with some finding that children who play with blocks significantly outperform those who do not, not just in infancy but over their entire academic careers.

In a modern nursery or kindergarten, one might expect such an old-fashioned learning aid to have been pushed aside by plastic construction toys or digital playthings. But unit blocks are still standing. The National Association for the Education of Young Children, founded by Hill, still recommends both the original form and variants such as cuisenaire rods, which are colour-coded according to their length in units. Today's children enjoy block-related activities that would not have seemed out of place in Fröbel's kindergarten in 1852, Pratt's City and Country School in New York in 1914, or the classroom depicted in a 1945 Life magazine feature on unit blocks. They may look simple, but unit blocks have been used to construct a surprisingly long-lived and sturdy educational edifice.