This study experimentally analyses traders’choices, with and without asymmetric information, based on the riding-bubble model. While asymmetric information has been necessary to explain a bubble in past theoretical models, our experiments show that traders have an incentive to hold a bubble asset for longer, thereby expanding the bubble in a market with symmetric, rather than asymmetric information. This finding implies a possibility that information symmetry promotes cooperation. However, when traders are more experienced, the size of the bubble decreases, in which case bubbles do not arise, even with symmetric information.