Trick 2 Just as large plates laden with food urge people to eat more, and big tanks stimulate goldfish to grow more, large shopping trolleys encourage people to buy more. First invented in 1937 to help people consume more than they could physically carry, shopping trolleys are getting bigger across the board. Psychologically, a full trolley signals generosity, abundance and a sense of completion – but it will cost you dearly. Shop 'til they drop: Concerns linger for retail landlords. Credit:Paul Jeffers Don't get snagged: Opt for the handbasket, carry purchases in your hands or, if you're feeling particularly silly season-ish, run around the aisles with one of those dinky kid's trolleys. Trick 3

Ever found yourself buying goat's cheese or jars of olives after trying a free in-store sample? Retailers don't offer them to cheer you up or fill your stomach. They're seeking to boost product sales – by up to 2000 per cent, according to one study. What's at work is the principle of reciprocity. Put simply, if someone does something nice – even just offering a slice of sausage on a toothpick – you feel compelled to return the favour. Don't get snagged: When you see a toothy sales assistant wielding a plate of pizza slices, be afraid, be very afraid and keep on walking. Trick 4 You're agonising over whether you paid too much for your father's new watch, or whether your mother even likes Chanel No 5. Cognitive dissonance is the name for that uneasy post-purchase stomach churn caused by simultaneously holding two or more conflicting ideas in mind. Retailers will do anything to stop you experiencing it – from sending "congratulations" emails, to spending on celebrity endorsements. You're less likely to look for a refund if you're happy with your purchase. Don't get snagged: Don't open your wallet without shopping around. If you do change your mind, you may not always be entitled to a refund under Australian Consumer Law consumer guarantees.

Trick 5 There's nothing like the fear of missing out to spark a stampede. The illusion of scarcity generated by triggers like "sold out", "last days" and "limited edition" supercharges our desire for a product. We're particularly vulnerable when purchasing presents for children. I once spent half a day searching for an elusive Terrainiac toy, and the other half crowing about finding one. It died the second it was tossed in the pool – albeit contrary to the manufacturer's instructions. Don't get snagged: An artificial sense of urgency makes people far more likely to part with their cash. Pause and take a few deep breaths, to make sure your spending decisions are sound. Trick 6 The unrelenting onslaught of Christmas carols sends retail employees half mad, but it makes shoppers spend 17 per cent more. The reason, says Brandwashed author Martin Lindstrom, is that Christmas music invokes a pleasurable state of nostalgia, or "rosy remembering". Other sensory cues stimulate spending too – think the olfactory overload of Lush or the dim meditative lighting of Dusk.

Loading Don't get snagged: Keep your hands to yourself. Bring headphones and listen to your own playlists. Personally, I think there's nothing like Rage Against the Machine to curb spendthrift tendencies. Denise Cullen is a writer and provisionally registered psychologist. Twitter: @CullenDenise