Numerous experimental studies have shown that background music affects consumer behaviour in a retail environment. Some of these have tested the degree of congruence between the music played in the store and the type of goods sold. An experiment was carried out in a flower shop, where love songs and romantic music (congruence condition), pop music (music usually played in the flower-shop) and no music (control condition) were played. The results show that the mean amount of money spent was significantly higher in the love songs and romantic music condition compared with the other two, whereas the pop music condition did not lead to an increase in the amount of money spent compared with the control, no music, condition.
Source: “‘Love is in the air’: congruence between background music and goods in a florist” from The International Review of Retail, Distribution and Consumer Research, Volume 19, Issue 1 February 2009 , pages 75 – 79
If you’re curious about why we buy then I suggest you read the aptly titled: Why We Buy: The Science of Shopping.