Dutch professor Bart Shultz joined Down to Business today to discuss the psychology of shopping. He is part of a growing movement that is contradicting the classical economic assumption that buyers act rationally.

He argues most of our decisions are irrational and driven by subconscious decisions that can be manipulated by retailers.

"The interesting thing is that we are not aware of it when we think about ourselves. We think of ourselves as rational beings," he says.

Mr Schultz suggests up to 95 per cent of our consumer decisions are driven by "emotion and instinct" rather than rational thoughts.

The psychologist says "consciousnesses is comfortness" and we have a habit of making "post-decision rationalisations"  to try to retrospectively rationalise the irrational decisions that we make.

He uses the example of a big purchasing decision, like buying a car or a house, to explain how the buyer's mind works.

Mr Shultz reasons that consumers are unlikely to make a spreadsheet laying out each of the hundreds of factors that should be taken into account when making such a big decision.

We make an approximation of these factors and follow our instinctive "gut feeling" and make a decision.

The professor ran Bobby through some of the implications of this way of thinking, including the ways that sellers can trick us into making irrational decisions, and the implications that these theories have for how we think about market research.

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