As a lonely child in Brooklyn, Dr Pepperberg owned pet birds from the age of four, and daydreamed about being able to understand animals' thoughts.

ECONOMIST: Alex the African Grey

Of all the needs (there are none imaginary) a lonely child has, the one that must be satisfied, if there is going to be hope and a hope of wholeness, is the unshaking need for an unshakable God.

FORBES: Thoughts on Children

His desire to make a difference has seen him working with charities such as Oxfam and SOS, while in 2009 he spoke at the United Nations' Summit on Climate Change in New York -- a far cry from his early days as a lonely child in Benin.

CNN: April 10, 2012 -- Updated 1528 GMT (2328 HKT)

Sartre was a lonely and fatherless child, raised by a doting mother and a professorial grandfather.

ECONOMIST: Jean-Paul Sartre

Here are six things an adult child can do to keep our aging parents safer when they get lonely.

FORBES: What to Do When Dad Is "In Love" With A Caregiver