Preferential ordering of content when comparing two items side by side

Question

When comparing two items side by side, is it better to show the given or known item first or show the unknown variable first?

I have a tabbed interface to show the differences of common eye issues compared to a normal eye. The tabbed interface is a fixed UI parameter and in this context is intended for a user to browse various eye ailments to compare a graphic side by side with a normal eye.

The common eye content will be the same across each tab. In this setup, I'm assuming a user will perform a rollover action over multiple eye-disorders in a session.

Is it best to place the common eye graphic on the left or on the right?

Answer 1

You could do either, depending on how you want to present the information. Do you want to emphasize "normal" or are you trying to emphasize the "non-normal" condition? Users will tend to scan from left-to-right - placing the object you want emphasize to the left would make sense as a result.

Because the "normal" condition is common across all tabs, you can also remove it from the tab's scope. You can organize the visuals in a way to further emphasize one condition over another. It also does not trick the user into thinking both graphics might be changing - the tabs clearly relate to just one graphic, not both.

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