Bankers recognize that a deep-rooted ethical culture is the best way to prevent bad behavior. But hampered by the difficulty of defining culture and spurred on by regulators' misguided advice, they are going about cultural change backwards.

Instead of starting with a clear principle to powerfully drive culture, banks are first focusing on policies and procedures they hope will ensure regulatory compliance. They are also increasingly monitoring and analyzing employee behavior for signs of trouble. The hope is that the sum of these parts will be a strong, healthy culture.

Regulators like Federal Reserve Board Governor Daniel Tarullo admit that they can't measure culture — only behavior. Thus they unintentionally divert energy and attention to compliance rather than to overarching culture. Yet culture is the most comprehensive way to pull all of the disparate parts of a financial firm together and get them moving in the same direction for the long term.

Quite simply, culture is the common purpose that employees are committed to and the energy they expend to achieve it. The most powerful and effective common purpose is to put the customer's interests first.

That's hardly a new idea. But when leaders expect it to be put into practice, rather than simply occupy the boilerplate "Values" section of their firms' websites, it can provide an unequivocal and unwavering guide for everything that employees do within an organization. Instead of waiting (often in vain) for overly rule-determined behavior to transform culture, leaders see culture transforming behavior.

As BlackRock chairman and chief executive Laurence D. Fink wrote in the firm's 2013 annual report, "We believe that if our employees seek to act always with integrity, performance follows." The firm has long been known for a customer-first culture that permeates all functions, even those like audit and risk management that are not customer-facing. Leadership constantly promotes that common purpose, and prospective hires — no matter the position they are seeking — must demonstrate that they genuinely understand what it means.

Another financial institution, Huntington National Bank, decided to put customers at the center of its operations at a most unlikely time: early 2009, in the midst of the financial meltdown. While the majority of banks were focusing almost exclusively on survival, new CEO Steve Steinour focused Huntington on the customer.

Instead of trying to gain every penny from consumers, Huntington offered free checking with no minimum balance, forgave penalty fees, granted a 24-hour grace period for checking overdrafts and began clearing transactions chronologically, instead of by size. (That last change cost the bank $30 million in fees in 2013.) Huntington also greatly increased loans to small businesses at a time when other banks were tightening credit.

Rather than create cultures of compliance, organizations like BlackRock and Huntington have created cultures of conscience. Their focus on the clear, unambiguous purpose of putting customers first enables them to achieve several goals.

They can inspire all employees with a purpose they feel passionate about, while providing them with a simple guide for any decision anywhere in the organization — from the C-suite to the mailroom. When weighing a dilemma, employees need only ask themselves if the action they are taking is right for the customer — knowing that they will be held accountable for the answer.

A customer-first culture also short-circuits self-interest and tribal behavior, cutting across the many subcultures typical of large financial institutions. BlackRock expects its employees to have a strong working knowledge of the firm beyond their core responsibilities, so that allegiance to a function or sub-group doesn't trump the firm's overall commitment to customers.

Moreover, the simplicity of this common purpose can be easily translated into policies and procedures that encourage adherence to its spirit. Overly elaborate rules tempt people to operate as close to the line of compliance as possible. An industry-wide study undertaken by a leading global bank concluded that 70% of what the researchers identified as conduct detrimental to customers was compliant.

What's more, this common purpose drives strong business results. Since 2010, Huntington's profits have doubled. BlackRock, which was specifically set up to help customers better understand risk, has grown to become the world's largest asset manager.

It's a virtuous circle. Common purpose drives culture; culture drives behavior; behavior drives customer loyalty; and increasing customer loyalty reaffirms the common purpose. And according to business loyalty expert Frederick F. Reichheld, a 5% increase in customer retention in such industries as banking and insurance yields a 75% increase in how much customers spend over time.

Optimizing business performance by treating customers the way we would all like to be treated is something that many financial institutions have done well in the past. There is no reason they can't do it again.

Robert Sloan is managing director and head of executive talent assessment at Sheffield Haworth, a consulting and advisory firm. Dr. Leo Flanagan is the founder of The Center for Resilience. Follow them on Twitter@Robertnsloan and @LeoFFlanagan.