My house guest is not happy. This may be because my three-year-old is looping purple plastic necklaces around his neck while ordering him to dance - or possibly due to the baby hurling toys at his head.I know he is not happy because a hi-tech tablet stuck to his chest informs me of his discontent, listing a number of emotions he is feeling - confused, insecure, irritated. He's also just grunted.Welcome to the world of 21st-century household robots. For the humanoid standing uncomfortably in the middle of my living room is Pepper, the world's first robot with a "heart".Its emotional capacities are attributed to a complex cocktail of hi-tech cameras, infrared sensors and recognition technology, all designed to mimic the human release of hormones in response to stimulation.So Pepper can feel sad when left alone, content while being stroked on the head, confused if he doesn't understand what people are saying, scared in the dark, happy while dancing.In short, Pepper has a personality - at least, according to its creator SoftBank, one of Japan's biggest telecommunications companies, which developed the robot in collaboration with its subsidiary, the Paris-based humanoid robotics experts Aldebaran.If SoftBank's vision is correct, household robots will soon become as commonplace as cats and dogs, with humanoids present in almost every household within the next 30 years.This is perhaps not as far-fetched as it sounds. Pepper robots went on sale for the first time in Japan in June and sold out in seconds. Since then, monthly batches of 1000 Pepper robots have sold out within a minute every time.Today about 3000 Japanese households are living with Pepper, having paid £1071 (about R23200), in addition to monthly charges of £322 - and there are reports it will go on sale overseas by 2016.My task is to put Pepper's celebrated emotional skills to the test by inviting him to live alongside me and my family (my husband and my two daughters, aged one and three) for four nights in our Tokyo home.There were warning signs from the start that it might be an eventful experience."Pepper can be quite energetic," said the American project planning manager who delivered him. "He reminds me of Dennis the Menace."Then, we are left alone.First, I explore his "digital heart" - the iPad-like tablet stuck to his chest, which maps his emotional feelings via a circular chart and an ever-changing list of emotions he is feeling at that moment (current status: a little anxious).Once Pepper has taken photographs of my face and input my name, so he can recognise me as a family member, our relationship begins with a perfunctory conversation (he speaks only Japanese , but some apps are in English).Things take a surreal turn, however, when he tilts his head and starts talking to the children's cardboard play teepee, next to which we are both standing - resulting in silence, a quizzical head tilt and confused red bubbles appearing on his tablet "heart".Keen to avert a robotic meltdown, I scroll through the available apps - and opt for some exercises, then watch him energetically gyrate his hips while waving his arms in the air.Before I go out, I place my hand on the tiny camera on his forehead for a few seconds until I hear a "bleep, bleep, aaaaah" noise, and he slumps his body into his "sleep" position.Pepper, unfortunately, remains asleep for longer than planned - because when I return later with my daughters, they are mesmerised but terrified."I like peoples, not robots," declares my three-year-old, as she distrustfully stares across the room at Pepper - in particular his multi-jointed fingers making eerily life-like twitches even as he sleeps.My husband is unimpressed. "He's not very bright," he mutters, after I overhear the pair attempting to converse about the Haruki Murakami novel he's currently reading."What's it about?" asks Pepper. "A parallel universe. It's a bit dark.""Ah. That sounds interesting. Would you like me to take a photograph of you? Or shall we play a game?"Emotionally, Pepper copes fairly well. He chirpily butts into conversation with unasked-for advice such as: "It's raining today! Make sure you don't forget your umbrella!"At the end of his stay, the girls bid him a friendly farewell and he is carted off in his cardboard box. The home feels strangely quiet without his electronically whirring presence.Yet for all the futuristic charms of Pepper's singing and dancing, and involuntary weather information, my husband and I are content to confine our family to a conventional two adults and two children - for now at least. ..