I buy popular brands I see on ads often enough (especially if you consider food items). Granted, there was a reasonable chance I was going to buy the products anyway, but seeing the ad probably raised the chances. I think every time I thought about the product, there was a chance that I was going to pull the trigger on buying it, and seeing the ad prompted another thought about the product. Also, when I see ads, I often have a thought like "I see this ad more often than the competitor's ads. Are they doing better? Maybe it really is because their product is better than the competitor's".