Little Billy Taylor crawls along the floor and dips his hands into a pile of what looks like wood shavings. He plays around in them for a few minutes before moving his attention to classmate Jessica Boswell who is playing with a golf ball rolling around in a tray of green paint. With similar enthusiasm, the one-year-old dives into the paint with both hands, squelching it between his fingers and then rolling the golf ball over his face, smearing the paint in and around his mouth. It's a scene which would have most parents and helpers frantically reaching for wet wipes. But here Billy and Jessica are left to enjoy the full sensory experience of feeling, smelling and even tasting the paint. Despite appearances, it really is good clean fun. The shavings are a bran-based breakfast cereal mixed with uncooked brown rice and the paint is toddler-safe, made by paediatric occupational therapist Linsey Irvine. In fact, Irvine has orchestrated every messy encounter the two will make in their 45-minute session. Everything Billy, Jessica and their classmates at Sensory Tots encounter has been carefully planned to help stimulate sensory integration - the process in which our brain is able to process the messages we receive from all our senses together so we can react to the world around us accordingly. The class is one of several that have sprung up around Hong Kong in recent years which target the sensory development of young babies and toddlers. Irvine, who has been involved in sensory integration for 10 years, runs the classes in Sai Kung and at Parkview in Tai Tam. Similar programmes are offered by Spring in Wan Chai, Leapfrog Kindergarten in Sai Kung, Sensational Baby in Quarry Bay, and at Spot in Central and Wong Chuk Hang. The importance of sensory integration was first highlighted in the 1970s by pioneering occupational therapist Anna Jean Ayres. However, recent technological advances in mapping brain activity have shown just how important it is and how we need it for almost everything we do, including running, eating, closing a door or ironing. It is something that should develop normally when children have sensory experiences. But in some cases, one or more of the senses fails to integrate efficiently leading to sensory processing disorder or sensory integration disorder. Classes such as Irvine's are aimed at supporting normal sensory development in young children through activities that engage all the senses. Contrary to popular thought, we are born with seven rather than five senses, says Irvine. In addition to vision, hearing, touch, taste and smell, we also have the vestibular and proprioceptive senses. "The vestibular system is all about movement and helps with balance," says Irvine. "It's a bit like when you hang a picture and you use a spirit level to see if its level. You have a similar system in your ear. "The proprioceptive system is our body awareness. It helps tell us about the position of our body parts and makes us aware of the speed and force of movement. "For example, if a child slams a door they have used too much force. If they write and they press so heavily with their pencil that they tear the paper, they need to work on their proprioception." According to Irvine, it is never too early to start helping a baby develop sensory integration; her classes target children between three months and 36 months. Children with poor sensory integration might find it difficult to pay attention in class. They might be the child who acts like the class clown Linsey Irvine, paediatric occupational therapist This week the children are experiencing the world of an astronaut. In addition to getting to grips with the surface of the moon (the bran mix) and the planets (golf ball rolled in paint) they are encouraged to stand on the moon (textured rubber bricks) and are given the chance to smell and taste some space food (freeze-dried fruit which melts in their mouth). Later they sit listening to music under a black blanket decorated with fluorescent stars, mesmerised by the changing colours of fibre-optic lamps. With each activity, Irvine explains the benefits to the carers. Even the music playing is pitched at a level to help develop the babies' auditory system. "For example, with vision, our aim is to work on depth perception and near and far vision so when they start to crawl they can see the floor, manage the change in depths and be able to focus so they can crawl to mummy and daddy," she says. "Everyone wants their baby to walk and talk and interact more. The sensory work and development helps secure the foundational skills which will help with all of those." For the parents, many of whom live in small spaces, part of the attraction of the classes, says Irvine, is being able to let their little ones make a mess and then not have to deal with cleaning up afterwards. "In Hong Kong we are slightly limited in terms of [open] space and parks," she says. "Also, it is often too hot for children to play outside. This means they don't get the opportunity to play in the grass and mud like they would if they lived somewhere like Britain where they could run around in their own back gardens." Virginia Spielmann, the clinical director of Spot (speech, physio and occupational therapy) which has run sensory integration programmes and courses for children and education professionals since it opened about five years ago, says some of the activities would occur naturally while caring and playing with baby. But in the modern world where children move less, carers must be aware of the importance of sensory integration involving all seven senses. "They are a real part of the neural development of a child and our ability to organise ourselves as adults," says Spielmann. "We all have to integrate information from all our senses but because our children are moving less and sitting still earlier there is a need to be conscious of the importance of movement for academic success and holistic child development. "Previously, it happened more naturally because children were going out and sitting on a tyre swing, scootering down a hill, building things, and getting mucky and dirty. Now as soon as they can sit they are being put into chairs and learning the alphabet, which is a very different way of looking at child development." The benefits go way beyond helping development in the first few years. Research shows sensory integration helps children become more focused and skilful in activities they do daily and lays a solid foundation for the skills they need in school, into their teenage years and adulthood. The consequences of a lack of sensory integration development can be wide-ranging, affecting attention span, fine and gross motor skills, and the ability to perform routine tasks. "They [children with poor sensory integration] might find it difficult to pay attention in class," says Irvine. "They might be the child who acts like the class clown, the one who is always looking for movement." Back in the Sensory Tot classroom, young Jessica has her nose almost squashed against a full-length mirror as she stares at her own reflection and that of her mother Zoe Boswell. Boswell believes the sessions are good for Jessica and enjoys how Irvine makes them educational for the parents. "The messy stuff is a bit out of my comfort zone," admits Boswell. "At least we don't have to clean up the mess afterwards."