Sensitive periods
A sensitive period is a stretch of early childhood when a child takes in one kind of learning, such as the sounds of speech, with an ease that later ages do not have.
Language is the clearest case, and the sandpaper letters are built around it. The Montessori Method (1912) says small children are at first particularly sensitive to single sounds of speech, then to syllables, and only then to whole words. The sandpaper letters start at the same place: single sounds first, and the lesson asks for the sound, never the letter name.
A window that closes
The same chapter puts the growth of spoken language between the ages of two and seven, and says only at this age can a child take in every sound of a language. An adult who learns a new language keeps a foreign accent. A child under seven who hears several languages at once picks up each accent whole.
She makes the same case for the senses. The child between three and seven, she writes, is in the period of formation of the senses, and that is when to help them develop. She built the sensorial lessons for those years.
It arrives suddenly
Her 1917 book adds that this growth comes in bursts. From one day to the next the baby cuts a tooth, says a first word, takes a first step, and once the first one comes the rest follow.
AMI's glossary today calls them transient periods of sensibility, in which specific sensitivities urge a young child to activity.
Using it at home
Watch for the burst more than the calendar. The age on each lesson page is a typical window, and a child who suddenly points at every letter on a sign is telling you the window is open now. A child who shows no interest yet is telling you to wait a few weeks and offer it again.
Sources
Passage numbers point into the public-domain texts this site checks every citation against.
- The Montessori Method, Maria Montessori (1912), ch. XIV and XVIII, passages 39863:306, 39863:429, 39863:431: Small children sensitive first to simple sounds, then syllables, then words; articulate language develops between two and seven, the only age at which every modulation of a language is acquired; three to seven as the period of formation of the senses.
- Spontaneous Activity in Education, Maria Montessori (1917), ch. IX, passage 24727:123: Development comes suddenly: from one day to the next the first tooth, the first word, the first step.
- Glossary of Montessori Terms, Association Montessori Internationale (read ): Transient periods of sensibility in which young children are urged to activity by specific sensitivities.
To see this at work across a whole area, the language lessons list every lesson in order, with its age and materials.
Related terms: planes of development, three-period lesson, normalization. All eight are in the glossary.