For more than a century, psychology and management science have tried to answer a deceptively simple question:

What makes a great leader?

We have developed theories, models, questionnaires and leadership programmes. Yet leadership remains remarkably difficult to predict. Burns even described leadership as one of the most studied and yet least understood concepts — and there is still no universal definition of what leadership actually is.

Perhaps part of the problem is not that our theories are wrong.

Perhaps we are simply missing a layer.

From the “Great Man” to the measurable leader

One of the earliest approaches was the Great Man Theory, associated particularly with Thomas Carlyle. Its premise was straightforward: leaders are born, not made. Certain exceptional individuals supposedly possess qualities that naturally predestine them to lead.

Leadership research eventually moved away from this heroic view toward trait theories. Instead of searching for extraordinary men, researchers began looking for measurable characteristics distinguishing leaders from non-leaders.

Intelligence, integrity, honesty, maturity and — interestingly — stress tolerance were among the characteristics associated with leadership. But Stogdill's work challenged the idea that one fixed collection of characteristics could define a leader. Leadership qualities appeared to depend partly on the situation in which leadership occurred.

That was an important shift.

The question moved from:

“Who is a leader?”

toward:

“How does this person lead in this particular environment?”

Situational and contingency approaches subsequently argued that there is no single ideal leadership style; effectiveness depends upon context.

And then leadership research made another important move.

Transactional leadership: performance through exchange

In the transactional model, leadership becomes an exchange.

The leader defines objectives and responsibilities, establishes expectations and links performance to consequences or rewards. Bass and Avolio describe important components including contingent reward and management by exception.

In simplified terms:

I establish what needs to happen. You perform. Performance has consequences.

There is nothing inherently primitive about this.

In fact, transactional leadership can be extremely effective. The literature in the papers shows that active transactional leadership can work particularly well in highly structured environments and is also frequently used by effective sports coaches.

But humans are not merely systems responding to rewards and corrections.

Which brings us to transformational leadership.

Transformational leadership: beyond the transaction

Transformational leadership, strongly associated with Bass and building upon Burns and House, goes further.

Instead of simply obtaining the required performance, the transformational leader attempts to inspire people to perform beyond their original expectations. Communication becomes more bidirectional, and leadership operates through affective, cognitive and behavioural mechanisms.

Bass describes four central transformational behaviours:

Idealized influence.
Inspirational motivation.
Intellectual stimulation.
Individualized consideration.

This is an enormous development from the Great Man idea.

The leader is no longer simply the heroic individual at the top. Leadership becomes relational. It includes trust, motivation, communication, intellectual challenge and consideration of the individual.

Research reviewed in the material associates transformational leadership with greater intrinsic motivation, effort, satisfaction and perceived leader performance.

These are valuable approaches.

But I believe we now need to ask the next question.

What happens inside the leader?

We have spent decades observing what leaders say, what they do, how they describe themselves and how other people describe them.

But what happens biologically when leadership becomes uncomfortable?

Imagine two executive candidates.

Both have impressive CVs.

Both score well in an assessment.

Both understand transformational leadership.

Both know exactly what to say when asked about empathy, resilience, conflict or pressure.

Now ask an unexpected and uncomfortable question.

One candidate's nervous system reacts strongly — but returns towards baseline rapidly.

The other's reaction remains elevated long after the question has passed.

That difference interests me.

How quickly does someone recover after an awkward question?

What happens to autonomic arousal when their competence is challenged?

What happens when they lose control of the conversation?

How does their physiology respond to criticism, ambiguity or social pressure?

Can they regulate while simultaneously thinking, listening and making decisions?

And what happens in the brain while all of this is occurring?

This is where I believe leadership assessment needs to evolve.

From psychometrics to neurophysiology

I am not suggesting that we throw away established leadership psychology.

Quite the opposite.

Great Man Theory, trait approaches, situational leadership, transactional leadership and transformational leadership represent stages in our increasingly sophisticated attempt to understand human leadership.

But the next stage should add another dimension:

biofeedback and neurofeedback-informed measurement.

HRV, respiration, electrodermal activity, muscular activation and EEG-derived measures can provide additional information about how a person responds during a controlled challenge.

Not as a neurological “lie detector.”

Not as a machine that declares someone a good or bad leader.

And certainly not as a replacement for interviews, behavioural observation, psychometrics or professional judgement.

But as another layer of data.

Because there is an important difference between somebody telling us:

“I perform very well under pressure.”

…and observing how that person's nervous system actually responds when pressure is introduced.

There is also a difference between reactivity and recovery.

A strong physiological reaction is not necessarily a weakness. The more interesting question may be:

How effectively does the system reorganize afterwards?

That could add an entirely different dimension to executive selection, leadership development and high-performance assessment.

Leadership assessment needs to look inside

The leadership literature itself has progressively expanded its perspective.

First we looked for the exceptional person.

Then we looked for traits.

Then behaviour.

Then context.

Then the transaction between leader and follower.

Then transformation, relationships, motivation and influence.

The logical next step, in my view, is to include the regulatory system of the human being who is doing the leading.

We should continue asking whether someone can inspire.

Whether they can communicate.

Whether they can set goals.

Whether they demonstrate integrity.

Whether they understand people.

But perhaps we should also ask:

What happens inside this person when things stop going according to plan?

Because leadership rarely fails during the rehearsed presentation.

Leadership becomes visible when somebody is challenged, surprised, criticised, frustrated or placed under genuine pressure.

If we continue evaluating leaders exclusively from what we can observe from the outside, we may simply keep eating the same old soup — reheated and renamed every few decades.

The theories are getting better.

Now our measurements should evolve too.