Dr. William Lee was the 2nd recipient of the Skeffington Award, in 1972. In his book, Each Of Us An Island, he describes “those systems which form the building blocks of the manner in which man performs.” I have chosen to to focus on his chapter on time and direction. Time and direction are the building blocks of all perceptions, not just visual perception.
Our sensory systems measure energy, such as sound waves, pressure, gravity, or, in the case of the visual system, light. In addition to intensity, these measurements include discernment of time and direction: the length of time the stimulus is present and the direction in which the stimulus is traveling when the measurement is made. All the sensory systems can measure time, but the visual system is the most accurate system for measuring both time and direction. Think of a blind person trying to navigate in an unfamiliar environment. They may depend upon a sighted individual or guide dog to help them obtain accurate directional information.
Time and direction are an integral part of perception. Without direction, there is no beginning or end, only on or off. Motion or movement is the combination of time and direction. Understanding movement (either of oneself or other objects) requires the visual processing of time and direction. Without an ability to use vision to make judgements about time and direction, the individual will have difficulty performing activities that require movement. Imagine that you have an appointment that requires you to be at a certain location at a certain time. In order to get there, you have to know where you are starting from. If you do not know where you are, it is impossible to know in what direction to proceed or how long it will take to get there. Now imagine that you are playing baseball. How will you know when to swing the bat if you do not know the direction from which the ball is coming and the speed at which it is traveling? Finally, imagine you are a second grader trying to read a book. In order to read efficiently, you must make make small eye movements called saccades moving from left to right. If you cannot coordinate the timing and direction of the saccades, reading becomes very difficult.
Since time is infinite, stretching from the past, throughout the present and into the future, processing time requires breaking this timeline into intervals. Let us look at a behavior, such as learning to write your name. The first time you perform this activity, you have no basis for comparison. The second time you perform this activity, you are able to compare your experience to past experience. You can also anticipate what resources you will require to perform this again in the future. Through these intervals of time, or cycles, we are able to learn. If performance does not improve through these rhythmic intervals of time, then perhaps the individual does not possess the requisite skills. The other possibility is that the individual is not able to use vision to accurately process time, and performs the right activity, but at the wrong time. You turn right but at the wrong intersection; you swing the bat, but too late; you move your eyes to the next line of words, but you haven’t read the last few words on the first line.
Now consider performance of complex behaviors that require the coordination of several systems. Think about the baseball player, but now he is in the outfield. He sees the batter swing, he hears the sound of the ball hitting the bat, and he has to move in the right direction to catch the ball at the right time. He has to coordinate all this information arriving at his sensory systems at different points in time and respond by accurately moving in the right direction through an accurately determined time interval. Difficulties processing time and direction visually will make it impossible to perform this task successfully. What if the outfielder is an 8th grader? The information he is receiving is constantly changing due to his fast growth rate. His past experiences are no longer reliable. He has to constantly rebuild the coordination of all systems to perform successfully.
Visual processing of time and direction is essential to coordinated performance. Many learning disabled children have difficulties in this area. The result is often more accurately described as a “living disability” because these children have difficulty, not only in school, but at home and at play. What can the developmental optometrist do to help the child who has difficulty with these skills? Vision therapy will often include activities aimed at improving rhythm. Providing an external clue to organize sensory inputs will support the motoric response or output. These activities may involve the use of the metronome, music, flashing lights, hand clapping, swinging balls, and trampolines. Activities can be done at home to enhance self-directed awareness of time intervals, such as skipping, jump rope, marching, or tapping the foot and clapping the hands to various patterns. As the ability to process time improves, activities which require directional movement and the integration of the sensory systems can be incorporated into the therapy program. Improving rhythm will improve the child’s ability to process time and direction. The result is the ability to do the right thing, at the right time, in the right place. Success.