Human beings frequently make hand movements whilst they are talking. These gestural movements are often imagistic in form, iconic in terms of their mode of representation and co-occur alongside the speech itself. There has been considerable debate in psychology over many years about the function of these iconic gestures, but it is now clear that they often convey core parts of the underlying message. Since we have little conscious awareness of these movements, they can be particularly revealing - we control what we say in our speech but find it difficult, or impossible, to control the content and form of these gestural movements. Their form and 'meaning' may not match the accompanying speech and these gesture-speech mismatches can indicate various underlying psychological states, including attempts at deception, and various dissociative attitudinal states. I will illustrate this with recent research conducted in our lab into the contrast between self-reported explicit attitudes to sustainability, in the context of climate change, and underlying and unconsciously-held implicit attitudes (measured using the Implicit Association Test), where certain gesture-speech mismatches arise as participants discuss their views on sustainable patterns of consumption, and their own individual sustainable practices. I will argue for the essential unity of speech and iconic gesture in the transmission of thought and suggest that we have underestimated the considerable communicative significance of these movements. These iconic gestures make thought visible, and we are able, quite literally, to 'see' what people mean in everyday conversations.