While we may consider our memory as being essential to who we are, others consider our moral traits to be the core component of our identity, suggests new research.

Data collected from family members of patients suffering from neuro-degenerative disease showed that it was changes in moral behaviour, not memory loss, that caused loved ones to say that the patient was not "the same person" anymore.

"Contrary to what you might think — and what generations of philosophers and psychologists have assumed, memory loss itself does not make someone seem like a different person,” said lead researcher Nina Strohminger of the Yale University School of Management in Connecticut, US.

"Nor do most other factors, such as personality change, loss of higher-level cognition, depression, or the ability to function in daily activities," Strohminger noted.

"This is interesting because it shows that someone can change quite a bit and still seem like basically the same person. On the other hand, if moral faculties are compromised, a person can be rendered unrecognisable," Strohminger pointed out.

The researchers recruited 248 participants with family members suffering from one of three types of neurodegenerative disease: frontotemporal dementia, Alzheimer’s disease, and amyotrophic lateral sclerosis (ALS).

Both frontotemporal dementia and Alzheimer’s disease are associated with cognitive changes, and frontotemporal dementia is specifically associated with changes to frontal lobe function that can affect moral behaviour. 

ALS, on the other hand, is primarily associated with loss of voluntary motor control.

The participants, mostly spouses or partners of the patients, reported the extent to which their loved one showed various symptoms typical of their disease (rating each symptom as none, mild, moderate, or severe).

The results revealed that both Alzheimer’s disease and frontotemporal dementia were associated with a greater sense of identity disruption than ALS, with frontotemporal dementia leading to the greatest deterioration in identity.

The researchers determined that perceived identity change was strongly linked with change in moral traits.

These findings, published in the journal Psychological Science, suggest that moral capacities form the core of how we perceive individual identity.