Why IQ Testing Should Be Mandatory When Hiring for the C-Suite

Because Intelligence Isn’t Optional at the Top

The stakes are high when organisations set out to hire for the C-Suite, and so is the failure rate. Global studies suggest that 30–40% of C-Suite hires fail within their first three years, and up to 50% of senior leaders underperform or prove ineffective.

Why does this happen? It’s not a lack of experience, technical skill, or commercial acumen that causes leaders to fall short. It’s the absence of intelligence, as well as four other core traits. Traits that can’t be coached or taught on the job.

The five non-negotiable factors for successful C-Suite executives:

1. Intelligence (IQ) 🧠
2. Integrity 🧭
3. Humility / Conscientiousness 🤲
4. Curiosity / Agreeableness 🧩
5. Health and Energy ⚡

These factors are the necessary foundations for effective leadership, and they can be measured. But, just focusing on IQ testing, we know that intelligence, as measured through IQ or aptitude testing, is the single strongest predictor of success in a senior leadership role. Yet, in many organisations, especially at the board level, cognitive testing is skipped entirely. “We just assume they’re smart. They’re already senior” is a common view.

Boards often feel uncomfortable asking senior leaders to complete assessments. There’s a perception that it’s “beneath” someone at that level or that it signals a lack of trust. But the real risk lies in not testing.

Assuming something is not due diligence and that mindset often results in costly mis-hires, especially when candidates look sophisticated on paper, interview well, and offer glowing (self-nominated) referees, but may lack the intellectual horsepower required to lead complex organisations.

A candidate who interviews well doesn’t necessarily think well. Boards are often swayed by presentation, confidence, and experience, all of which are visible and easy to assess. But traits like strategic thinking, mental agility, and problem-solving under pressure? These require deliberate testing. Without it, boards are blind to critical risk factors in a candidate’s leadership profile.

Relying on intuition, gut feel, charisma, and experience alone is not enough. If you want more successful C-Suite executives and fewer costly leadership failures, you must test for what really matters.

Stop assuming, start measuring, and make it a standard part of the executive hiring process.

Want to improve your hiring process? Contact Fermion for expert psychometric testing solutions.