As a designer, why is it important to be concious of the gestalt principles?

It has been stated that we see far more than meets the eyes, though not always correctly, for we experience various phenomena of illusion using gestalt principles, departures from physical reality. Although they are errors, illusions are useful evidence of how eyes and brains normally work. When ever we gain inspiration, it’s often not just the particular element that sparks our artistic impulse; it’s the totality of the element and its surroundings. Grasping that totality concept, both the individual element and the whole in which it exists are important both separately and together, are essential to understanding how gestaltism influences our design choices.

It is important to use psychological techniques more in our designs but not completely scientific or mathematical, as stated by Michael Tuck that he believes the best design comes when proven theory works in harmony with art. At its simplest, gestalt theory describes how the mind organizes visual data. The stronger the clarity of form, the more effective the design.

See below examples how important we use the principles of gestalt:
This is called the "subjective triangle." What do you see when you look at the figure below?



The famous "Dog Picture," shown below, illustrates a Dalmatian dog sniffing under a stand of trees. When you squint at it for a moment, you see the dog "come together" from the disparate black and white blobs of the picture.

References: 1. http://www.answers.com/topic/illusions-1#ixzz1EtLlrd4P
                  
                  2. http://sixrevisions.com/web_design/gestalt-principles-applied-in-design/