Effect on tipping of barman drawing a sun on the bottom of customers' checks

Previous research has demonstrated that a pleasant drawing (a smiling face) on a restaurant bill increased the number of tips left by clients. A similar experiment was carried out using a drawing of the sun since it is known that tips increase on sunny days. The experiment was carried out in local bars and involved clients who have ordered an espresso coffee. Analysis showed that the drawing of the sun led clients to leave a tip more frequently than when this drawing is not present. The size of the tip left was also higher. The hypothesis of the creation of a positive frame of mind by this stimulus is discussed.