Children are often required to perform tasks that require them to cut paper with a pair of scissors. The simplest cutting tasks involve cutting along a straight line. Cutting angled lines, lines that require a sharp change in direction and curved lines all require increasing levels of sensorimotor control in order to achieve the desired result.
The basic components of scissor cutting
Cutting paper with a pair of scissors, involves several actions that need to be coordinated in time and space:
The hand holding the scissors:
- Grasps the scissors in a way that allows movements of the thumb and fingers to open and close the blades of the scissors.
- Opens and closes the blades repeatedly.: movements of the thumb and finger are used to open and close the blades.paper to produce a clean cut.
- Aligns the blades of the scissors at right angles to the paper to allow for a clean cut.
The hand holding the paper:
- Grasps and positions the paper relative to the blades of the scissors, so that closing the blades produces a cut in the paper in the desired direction.. .
- Repositions the hand on the paper in order to change the position of the paper relative to the scissor blades to cut in the desired direction.
Dynamic coordination between the two hands
The skill in cutting with scissors lies in the dynamic coordination of the actions of the two hands .
When cutting along a straight line drawn on a narrow sheet of paper, the dynamic interaction between the cutting and supporting hands is relatively simple.
The paper is held steady and at right angle to the scissor blades so that closing the blades makes a cut along the line. The cutting hand moves the blades forwards relative to the stable paper to produce a series of cuts in a straight line.
If the blades are not positioned at right angles to the paper, the paper will tend to slip between the blades. This happens in particular with children's craft scissors which are a little loose and nto very sharp.
As soon as I want to to cut a line that is angled across the paper, the hands are moved relative to one another, so that the blades are aligned in the right direction. I can keep the blades of the scissors still and change the relative position of the paper, or I can change the angle of the blades relative to the paper. Most often the movements of the cutting and supporting hand are dynamically coordinated to produce a cutting line in the described direction.
Depending on the size of the paper and the angle of the line, movement of the paper and blades is produced by a combination of movements of the wrist, mostly into flexion, as well as movements of the shoulder to position the hands in space.
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Cutting along lines on a narrow strip of paper
Cutting pieces off a narrow strip of thin card illustrates the fluent and dynamic interaction between the two hands. To start with the card strip is grasped fairly close the the first cutting line.
After I have cut across the first two lines, I need to move my supporting hand to allow access to the next few lines. In this instance I do it by grasping the strip of card in my cutting hand while I reposition my supporting hand. Once the strip is once more held by the supporting hand.
The card strip can also be supported by the blades of the scissors, which close just enough to hold the paper steady.
Video clip: adult cutting straight lines
In this video clip you see me cutting along straight lines. You will notice that in this activity I choose to support the strip of card by grasping it with my cutting hand when I want to reposition my support hand. Also notice how the actions of the two hands are seamlessly coordinated, and how the movements of one hand is timed to support the action of the other hand in a dynamic process.
Motor planning for efficient shoulder-forearm-wrist coordination
Adults and children with good cutting abilities will usually position the paper so that the lines of cutting is more or less in the mid-sagittal plane of the body, so that the hands hands can be positioned in a comfortable position close to the midline, and more-or-less facing each other (depending on the demands of the task).
In this video clip you see Rona, aged 8 years, cutting an A6 piece of thin card in half, and then the two halves into smaller rectangles. What is very apparent in this video is the way she positions the paper so the the cutting line lies close to th mid-sagittal line of the body. This is done with a smooth action and without hesitation.
Now take a look at Max, aged 4 years 6 months. His tendency is to hold the paper so that the line to be cut lies in a horizontal position and he can cut along the line by lifting the arm away from the body and positioning the scissors so that the blades are aligned with the cutting line.
Grasping the scissors
A standard pair of the scissors has two loops (sometimes referred to as holes) into which the thumb and fingers can be inserted.
The thumb is inserted into the smaller top loop. The index finger is usually rests on the outside ring of the bottom loop, and this positioning of the is thought to provide a measure of stability to the hand. However, this assumption is not supported by any evidence.
This 7-year-old, who has good cutting skills, does not position the index finger over the outside ring of the scissors.
If the index finger rests on the outer ring of the bottom hole, the middle finger along with the ring and pinky are inserted into the bottom loop, depending on the size of the loop.
In some scissors the bottom loop is just large enough to allow for the inserting on one finger.
Other scissors, including the craft scissors usually used by children, have a bottom loop that is is oval and big enough to accommodate 2 or 3 fingers, depending on the size of the scissors.
Generally the fingers make contact with the loops somewhere between the distal and proximal IP joints.
Finger movements for opening and closing the blades
With the fingers inserted into the loops of the scissors, coordinated movements of the thumb and fingers will lead to opening and closing of the blades.
The thumb plays a very important role in the producing the movement of the blades. When the blades are completely open, the thumb is extended, and closing of the blades is brought about by flexion of the thumb at the MP joint. These movements occur at the metacarpophalangeal (MCP) joint of the thumb.
The bottom loop is moved by flexion of the MCP joints of the fingers that are inserted into this loop. The interphalangeal (IP) joints remain relatively steady to provide stability to the scissors. Most of the movement occurs at the MCP joint of the fingers.
The coordination of shoulder and wrist movements
Adults, and older children with good cutting abilities, demonstrate effective interaction between the movements of the shoulder and elbow, and movements of forearm and wrist to position and angle the scissors and paper.
For the most part the upper arm stays relatively close to the body and the hands are brought to the midline by twisting in action (medial rotation) at the shoulders. The elbows are flexed and the forearms are twisted so that the hands face each other (The forearms are in neutral rotation.)
Small flexion movements of the wrist are used to change the alignments of the paper or the scissor blades.
This combination of a relatively stable position of the upper arm, combined with smaller movements of the forearm and wrists is typical when using the hands together to manipulate objects.
Younger children with less well developed coordination of shoulder/hand action for object manipulation tend to position the hands their hands using a combination of shoulder, wrist and forearm movements.
Max (aged 4 years) holds the scissors and paper with the hands well positioned as he starts to cut out a circle. But as he cuts along the curved he changes the alignment of the scissor blade to stay on the curved line, rather than adjusting the position of the paper..
It is also important to notice that the position of the arm is affected by the height of the table.
Here you see how max (aged 4 years) lifts his right (cutting) arm up to change the direction of the scissor blade to make a diagonal cut on the paper.
Development of cutting
Very young children cutting
From about the age of 2-3 years young children take an interest in cutting with scissors.
When children first start to cut with scissors they have difficulty opening and closing the blades of the scissors and at the same time holding the paper and keeping the blades of the scissors at right angles to the paper.
This video clip of Will (aged 2 years) beautifully illustrates different components of cutting with a pair of scissors that first need to be mastered and then integrated into a series of movements of the two hands working together in a coordinated manner.
Notice that at this age he hold the scissors with the palm turned downwards (pronation of the forearm) when he cuts. This clip also illustrates how a change in coordination can happen very rapidly. One day Will is still opening the scissors using two hands, but after a demonstration followed by a nights sleep, he changes to opening the scissors with them still grasped in the hand.
Also notice how the ring of the scissors slip right up to the base of the thumb, and the movements of the fingers are not well coordinated.
Movements become more efficient with practice
Over time and with practice the coordination of the shoulder, elbow and wrist movement actions become more efficient as the child learns use wrist movements to position the scissor blades and paper.
Younger children tend to use shoulder movements to align the scissors and paper.
Video clip: Max cutting out a circle
In this video clip you see Max cutting out a circle. The end product is quite good, despite the awkward looking movements of the shoulder he uses change the direction of the scissors. He does make some adjustments of the supporting hand on the paper, but these are quite late in the process and limited in scope. They mainly seem to serve to move the fingers out of the way of the scissor blades.
Video clip: Will (3 years 9 months) cutting a straight line
These pictures and the video clip beautifully illustrates how Will (aged 3 years 9 months) seeks different solutions to holding and aligning the paper to the scissors as he cuts in different directions. Will starts this activity with both forearms in pronation (hands turned downwards).
Video clip: Rona (3 years 6 months) cutting out a circle
Video clip: Will aged 7 years cutting out a circle
Rona (8 years) cutting out a circle
Rona cuts fast and does not cut carefully.
Will aged 7 years cutting along straight lines
In this video clip you see Will (aged 7) cutting along short lines drawn from the edge of a piece of card.