Books like StrengthsFinder 2.0 have helped leaders discover their strengths-but tend to stop there. Thuy and Milo Sindell argue that focusing only on our best abilities neglects a vital development opportunity. Inside every leader are 'middle skills,' hidden strengths that can be turned into full strengths with attention and focus.

Discover Your Strengths and the StrengthsFinder titles-has resulted in a very one-dimensional model for leadership growth, say Thuy and Milo Sindell. Their research and work have shown that, like everyone, you have hidden, undeveloped strengths that, if identified and worked on, can expand your repertoire of skills, make you a better-balanced leader, and significantly improve performance.

Everyone has what the Sindells call Default Skills, or obvious strengths; Deficient Skills, or weaknesses; and Hidden Strengths, or skills in the middle. Focusing only on Default Skills can lead to resting on your laurels. But trying to develop Deficient Skills isn't worth it. It takes too much time and effort to bring these skills up to speed-the ROI just isn't there. It's in the neglected middle skills that the most potent development opportunities lie. They're close enough to being strengths that working on them can offer a powerful payoff-they are Hidden Strengths.

Using assessments, exercises, and case studies, the Sindells help you identify your most promising middle skills-your Hidden Strengths-and create a plan to turn them into full strengths. In today's work environment, not growing and stretching yourself translates into lack of innovation, stagnation, and obsolescence. Relying upon strengths is like relying upon training wheels-at a certain point you need to take them off improve and grow.