THE tug of war between nurture and nature continues to divide experts in the fields of child development and education.

Are intelligence and cruelty hard-wired at birth, and are we therefore predisposed to certain behaviour before our first glimpse of daylight?

Or does the love and support of the family shape our conduct towards others? In which case, are children from violent or broken homes doomed to repeat the mistakes of their parents?

In Away We Go, an expectant couple contemplate moving halfway across America so that their child will be raised in a safe, loving environment, surrounded by positive role models.

The irony is that the beleaguered parents-to-be are far more emotionally stable and well-equipped to raise their baby than almost everyone they encounter during a madcap road trip scripted by novelists Dave Eggers and Vendela Vida.

After the emotional Revolutionary Road and Jarhead, Oscar-winning British director Sam Mendes (American Beauty) returns to the comedy genre with aplomb, demonstrating a light touch with his dysfunctional characters.

The film opens as it means to go on, with a hysterical bedroom scene introducing Burt (John Krasinski) and Verona (Maya Rudolph), who are blissfully happy in their ramshackle cabin.

With Verona six months pregnant, the couple try to find a new place to raise the baby with the help of Burt's parents Jerry (Jeff Daniels) and Gloria (Catherine O'Hara), who live in Colorado.

The old-timers throw a spanner in the works by announcing they are moving to Belgium before the baby is born, leaving their son and his partner with no support.

So Burt and Verona ponder moving to a new city.

The couple kick-starts a journey of exploration, visiting old boss Lily (Alison Janney) and her hen-pecked husband Lowell (Jim Gaffigan), who give parents a bad name.

An emergency telephone call forces a detour to Miami, and the expectant parents reconsider their definition of “home”.

Away We Go is an entertaining ensemble piece that paints a vivid portrait of contemporary America and its foibles.

Krasinski and Rudolph are instantly lovable, and we root for them as they come up against overly-officious airline check-in staff and relatives who clearly don't know best.

Janney is hysterically grotesque as a mother whose conduct will see her offspring in therapy for the rest of their lives, while Gyllenhaal is equally amusing in her colourful supporting role.

The narrative chugs along, covered in a thin veneer of sentimentality, towards an upbeat and life-affirming conclusion.