Several prominent universities have banned gifts from pharma companies, including everything from paid lunches to drug samples, and the trend seems likely to continue. Even the Grinch would be impressed by all the banished pharma gifting, the result of a system increasingly considered inappropriate in an environment where Congressmen and patients are demanding to know where physicians and researchers are having their bread buttered. 
If a sales rep manages to enter a clinic or practice—leaving products in her wake—does that suggest a doctor is on the take? Are doctors even cognizant of these factors of influence?
When Johns Hopkins announced its gift ban in early April, the policy surmised that “gifts, even small gifts, carry an implied expectation of reciprocity.” The policy went on to state that “industry influence may be subtle, and healthcare providers often are not aware of the extent to which their judgment may be influenced when they depend on industry to support educational activities or provide drug samples.” These conclusions were sourced to academic experiments and publications, with several articles in particular cited in a footnote.
One of the cited texts,  Bounded Ethicality as a Psychological Barrier to Recognizing Conflicts of Interest, focuses on an individual’s inherent blindness to conflicts of interest. The article argues that despite best intentions, ethical decision-making is hampered by an unconscious need to uphold a positive self-image. “Ethical decisions almost always involve consequences for [one’s] self and/or others, and it is this social component that brings forth a surge of self-oriented motivations in ethical decision-making,” the article said. Even worse, the authors reason that individuals are “unaware of their unawareness” to conflicts of interest, complicating matters further. The article concludes that motivational processes and psychological automaticity—behavioral cues below the realm of consciousness—are key players in the decisions we make. It is highly unlikely that we can avoid or recognize certain conflicts of interest, since our motives are at least partially unconscious.   
A second article tests responses to fiduciary exchanges based on concepts of value, reciprocation and trust—by analyzing brain wave responses. Getting to Know You: Reputation and Trust in a Two-Person Economic Exchange, published in Science, sets up an experiment whereby two individuals—an investor and a trustee—exchange money back and forth. In this scenario, the investor gives money to the trustee, with an implied understanding that he will be reimbursed by the trustee. The trustee is free to reimburse the investor completely, or give less back. After several exchanges—the trustee reimburses the investor with an understanding that he will provide more money—data shows that a “benevolent” reciprocity perpetuates itself by rewarding the behavior. Trustees offering a lesser amount tend to be punished with less money in the next round. This behavior matches brain waves that correlate with an “intention to trust.” 
“Benevolent reciprocity by the investor is expected to generate the intention to increase repayment (trust) in the brain of the trustee,” in terms of predictable brain signaling, the study found. 
What does any of this prove, in relation to industry support of physicians? Perhaps there are too many variables to make broad conclusions. But one thing is certain: the easiest way for a university to avoid conflict of interest charges, is to avoid pharma’s interests.