The purpose of this research was to discover whether the children (aged 9 to 11) were thinking while taking part in practical science activities. One method the author used was to video the activity and then watch the replay with each child in turn. She was then able to ask them what they had been thinking about at each stage. The majority of the children (21 out of 27) revealed that they had been thinking very little either during the lesson or subsequently. Out of a total of 195 minutes of activity caught on video only three conversations actually deal with thinking processes. Much time was taken up with discussing "turns" but children also urged others to keep "on task". There was a contrast in the way that the children expressed their ideas in the different contexts. In written tasks their answers were very brief and reflected the formal language they had been taught to use in tests. Most children used scientific terms such as "gravity" but with little further information to indicate their level of understanding. Implications of this study are discussed and suggestions for improving thinking skills in the primary classroom are offered.