Research published in the Journal of Consumer Behaviour challenges the notion that major trips to the supermarket are the best opportunities to create unplanned purchases. Jens Nordfalt found that those little fill-in trips that we take during the week, are likely to result in many unplanned purchases. What Nordfalt found was that, on average, unplanned purchases will account for a greater share of the total bill for a fill-in trip, than for a major trip (which contradicts much of the established thinking around how we shop).
NB. This is an excerpt from an earlier posting.