The eyes have it. Marketers are now using high-tech ways to decide what shape and color a wide variety of products should be to drive optimal sales.

The Wall Street Journal  reports companies like P&G, Unilever and Kimberly Clark employ 3D computer simulations of product designs and store layouts using retinal-tracking technology. It helps them figure out what your eye goes to, and is a much more reliable way to collect marketing info than old-fashion focus groups.

In just one example, Kimberly-Clark used computer screens outfitted with retina-tracking cameras to test new packaging for Viva paper towels in 2009.

Obviously, this whole world of marketing is way past the tired old retail axioms you've heard about the importance of putting products on end caps or having popular and profitable items at eye level on the shelves. Marketers are now figuring us out like guinea pigs!

So here's the thing: We all know the marketers are so clever and can greatly influence our purchasing choices. It's up to you to fight back and buy the best deal despite all the marketing efforts. And that will usually be a store brand or a brand that doesn't spend a lot on advertising or packaging.

Don't allow physiology and the psychology of human nature to draw you into overpaying. It's your wallet. Keep your money in it!