Yes, this is a part of reciprocity theory:
Over the past forty years, numerous studies in social psychology offered empirical support to reciprocity theory. Major findings can be summarized as follows: Receiving even a small favor leads to further compliance with requests of the person who provided the favor (Howard, 1995), even when the favor is unsolicited and unexpected (Regan, 1971), and even when a favor-giver is not perceived as likable (Goei, Massi Lindsey, Boster, Skalski, and Bowman, 2003). Receiving a favor in public conditions creates greater compliance than receiving a favor in private conditions (Whatley, Webster, Smith, and Rhodes, 1999). As the amount of time lengthens between the initial favor and the opportunity to reciprocate, the perceived need to reciprocate diminishes (Burger, Horita, Kinoshita, Roberts, and Vera, 1997).
Gender as a Moderator of Reciprocal Consumer Behavior
Additionally, DavePHD's comment is also supported by research. Several studies have been done on wine tasting, one of which says:
The results of the current study empirically supported previous experimental evidence that people feel appreciation and a need to reciprocate for what they have received. Therefore, if winery visitors find their experiences at wineries enjoyable, they are likely to develop a sense of gratitude and possibly a sense of obligation to return hospitality provided by the winery personnel. These feelings, in turn, may lead to a perceived need to buy wine or wine souvenirs at the end of their visits.
Additionally, the study aimed to investigate whether visitors of smaller and larger groups differ in terms of the amount of money they spend at wineries and with respect to feelings of gratitude and obligation. The results indicated that visitors who travel to wineries in smaller groups feel more grateful to winery personnel and more obliged to buy wine than those visitors who traveled in larger groups. Accordingly, visitors who travel in smaller groups tend to spend more money on wine than larger groups.
IMPORTANCE OF WINERY VISITOR GROUP SIZE
ON FEELINGS OF GRATITUDE AND OBLIGATION
And a similar thing happens with pharmacists who receive free samples and other gifts:
A research published in the American Journal of Bioethics in 2003  points out to the fact that physicians prescribe more medication to which they have access to free samples donated by representatives. Massud  confirms this finding by affirming that physicians who receive samples prescribe less and less generic medications and consequently contribute to the increase of expenses with medication.
Physicians and Conflicts of Interest