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Montessori Theory: The Key Concept of Isolation


Control of Error and Isolation of Difficulty are two critical aspects of Montessori. Each concept gives the child control over the pace of his development with an opportunity to self-correct. 

As a child leaves the unconscious learning period, where he effortlessly gathers impressions from his environment, and moves into the conscious learning period, he needs a system to classify the impressions.

Isolating the quality of material gives an opportunity to organize. Montessori isolated the qualities of objects to maximize the education of the senses and to give the child the opportunity to discover and understand the difficulty of the material without interference from the teacher.


Isolation of quality

Control of Error is automatic feedback that tells the child he needs to make an adjustment in order to complete the work successfully.

Subsequently, he learns to trust his own instincts: “the power to make progress comes in large measure from having freedom and an assured path along which to go; but to this must also be added some way of knowing if, and when, we have left the path.” (The Absorbent Mind, pg. 93)

Isolation of Difficulty is embedded within materials to help a child create order within his environment: “The difficulty that the child must discover and understand must be isolated in a single piece of material.

The isolation simplifies the child’s task for him and enables him to perceive the problem more readily.”  (Montessori: A Modern Approach, pg. 61)

The Materials

“Every series of objects… is graded so that there is a maximum and a minimum, which determines its limits, or which, more properly, are fixed by the use which a child makes of them.”
-The Discovery of Childhood 

Montessori created materials based on empirical observations of children. So we can actually claim that the materials were chosen by the children discarding any material not of interest, use or need – developmentally – by the child.  She carefully considered each of the senses.

Then she thought about how best to help children to clarify and to expand their existing experiences.  She focused on “systems of objects that share a definite quality, such as color, shape, dimension”. {The Absorbent Mind}

She set forth with preparing an environment that provided the opportunity for a child to interact very specifically with a material or a “quality”.  

Each group of objects represents the same quality but to different degrees. Each material emphasizes one particular quality by eliminating or minimizing other differences.

So, there is consequently a regular but gradual distinction between the various objects and, when this is possible, one that is mathematically fixed like the Pink Tower and the decimal system.

Every material contains a “control of error”, the ability for the child to self-correct and for the teacher to stand back to observe and then guide when necessary.  “This self-correction leads the child to concentrate his attention upon the differences of dimension, and to compare the various pieces.” {Montessori: A Modern Approach}

Within Practical Life, a spill on a tray exemplifies these concepts. Within Sensorial, the inset not fitting the template does the same. A map is also a good example. If you take a wrong turn, you’ll need to make adjustments if you are to get to your intended destination.

The Teacher

“The goal is that the child will develop a sense of satisfaction from the work itself, not be dependent on the approval of a teacher.” – The Montessori Controversy {pg.90}
If a teacher intervenes in the learning process, then Control of Error will not be an effective means of development for the child. With Control of Error, a child will learn to make his own decisions and to trust his instincts.

He develops confidence and the ability to problem solve. Montessori called children who reach this point “Normalized”, a term defined by qualities such as self-control, concentration, independence, empathy, and discipline.

Normalization is the main goal of Montessori education. Without Control of Error and Isolation of Difficulty, the goal will not be reached.

Furthermore, a teacher should never interfere with a child’s work with praise or punishment. If this happens, a child will feel inadequate, that he can’t guide himself, lowers his self-esteem and motivation, and discourages him.

Once the teacher trains on the method and prepares spiritually to direct a class, she must then focus on giving lessons and introducing the child to the materials. From there the child leads his learning experience with his own “hands” with “control of error” built into the works to enable auto-education.

The teacher‘s role is to observe and recognize when to intervene to direct the child back to an activity that suits his development. A child can only improve himself if given the opportunity to practice on his own by his own will for extended periods of time: “how much better it is to recognize my own mistakes, and then correct them?

If anything is likely to make the character indecisive, it is the inability to control matters without having to seek advice. This begets a discouraging sense of inferiority and a lack of confidence in one’s self.”

Errors correct themselves in time and with practice; their existence is unavoidable in life for always. Even in science, the goal is twofold: to measure a precise figure and to measure the extent to which that figure could be wrong or deviate from that “precise figure”. {The Absorbent Mind, pg. 248}

On a final note with regards to Control of Error & Isolation of Difficulty, materials aside, as a teacher, it is important to accept that we ourselves make mistakes and it is ok to allow a child to see that side of us:

“…it is well to cultivate a friendly feeling towards error, to treat it as a companion inseparable from our lives, as something having a purpose, which it truly has.” (The Absorbent Mind, pg. 246)

In addition to spiritual growth and self-awareness, a teacher must have faith in the materials and the child’s work with the materials in order to successfully serve the child. The aspects of Control of Error and Isolation of Difficulty work to achieve this goal.

Thank you for reading!


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