How we change what others think, feel, believe and do
When we see a line, our eyes tend to follow it. When the line ends, our eyes keep on moving in the direction that the line was going.
This continuation also happens when lines intersect. If two lines cross, we will tend to see it as two lines rather than four lines that join at a single point.
The eye will tend to follow the line below down and up the other side, and then shoot off the end a bit like a ski jump.
Perhaps it is no surprise that Nike has a very similar 'swoosh' shape as its brand logo.
A question in any visual image, particularly when used for persuasion, is 'Where is the viewer's eye going?' One of the basic dynamics is that the eye tends to find and then follow lines. One reason for this is to trace outlines and hence distinguish objects which we can then recognize and name, and so respond to in an appropriate manner.
We tend to visually follow straight lines in particular. If you see a photo of a road, your eye will travel down the road into the distance. Curves take more work and squiggles are harder skill. Perhaps sharp angles are worst as the eye has to sharply change direction.
When lines cross one another, this 'momentum' along the line we are following means we will go straight on rather than turn a corner or come to a standstill. The diagram below hence may be interpreted as just two lines which cross one another.
Looking at things we will often default to starting from the left and moving to the right. We hence tend to follow a line left-to-right more often than right-to-left.
When creating persuasive images, consider the locus of travel of the eye. Use lines to guide the eye appropriately. Remember to use straight or gently curving lines rather than zig-zags or scribbles and minimize lines which cross one another.