Science nerd Andrew (Rogen) is taking a cross-country road trip to pitch his new organic cleaning product. And in a moment of weakness, he invites his meddling mother Joyce (Streisand) to accompany him from New Jersey to San Francisco. She doesn't know that he has discovered that her old flame now lives there, and he thinks that sparking her love life might get her off his back. Of course, the trip doesn't go as expected for either of them, and incidents along the way change their relationship forever.

Fletcher's direction and Fogelman's script ground the characters in honest realism even in goofy situations, such as when Joyce enters a ridiculous beef-eating contest. But none of the set-pieces are played for wacky slapstick value; they're all focussed on the central theme that we all need to pay better attention to the people around us and hold our own impulses in check. No, this isn't a very deep message, but at least it isn't poured on with schmaltz.

Streisand and Rogen create likeable, rounded people who sometimes say and do stupid things. Streisand is especially watchable, delivering a layered performance that mixes broad comedy into both internalised drama and quiet emotional resonance. Joyce may be a typically over-involved Jewish mother, but she's also a middle-aged woman with needs of her own. And rather than rooting for Andrew to sell his invention, we just want Joyce to kick start her personal life.

Along the way, superb one-scene players add to the film's consistently amusing if never outright hilarious tone. Rather than laugh out loud at something funny, we're more likely to smile in recognition at these people's actions and reactions. And even the serious scenes aren't hugely demanding, either for us or for the actors. But it keeps us mildly entertained all the way through. So if the filmmakers avoid the story's potentially interesting edges, we don't mind too much.

themes, language, innuendo

21.Dec.12