What does all of this means? On some level of knowing, you knew that water always remains horizontal, yet many, many adults don't use this knowledge when they are faced with a task like this one where they have to draw in the water level. Instead, we tend to be misled by the tilt of the glass. Most people draw a line that most "off" from the horizontal when the glass (or other container) is at a steep tilt. If you have already studied the work of the famous Swiss psychologist, Jean Piaget, then you may have seen or read about this task. Piaget originally thought that the ability to represent the water level with a straight line would develop naturally and that most young teenagers would get questions like this one correct. Piaget overestimated general performance on this task. Many adults don't seem to know the correct answer.
Thinking About Spatial Information
Think carefully about the figures you just saw. The black lines you drew indicate the level of the water's surface. The red lines are the correct answers. All of the red lines are horizontal because the level of water remains horizontal regardless of the angle of the glass that is holding the water. Consider the differences between the lines that you drew and the correct lines. The extent to which they are "off," that is not the same line, is the extent to which you misjudged the water level.
How should you think about spatial information? A good strategy is to try to visualize the situation. Try to "see" in your mind's eye a glass of water being raised to someone's mouth. "Look" at the imaginary water level as the glass is being tilted. Visual imagery is a strategy often used by creative people as a problem solving tool. It is well worth the effort to develop imagery skills and to use them on a regular basis with a wide variety of problems.
