AbstractThe level of priority and resource given to the care of organisms is influenced by beliefs and understanding about their capacities for conscious awareness. Variation in attitudes to animal welfare around the world today is partly a reflection of this. Improved understanding of the range of phenomena of which animals may be conscious is likely to lead to greater global consensus about the importance of high standards of animal welfare. This is a matter of current relevance. In the global free market there is a danger that efforts in one country to raise standards for farm or laboratory animals will be compromised by competition from others which employ cheaper, less welfare-friendly systems. Scientific developments which inform us about animals’ capacities for pleasant and unpleasant feelings will play an important role in the development of global agreement about animal welfare standards. Deciding which animals might have the capacity for consciousness, and thus for suffering, and of what they might be conscious, are fundamental issues which set boundaries to the ranges of species to be given basic or special forms of welfare protection. In practice, such lines have to be drawn and it is crucial that they are drawn in the right place. This is a difficult but essential task and society looks to scientists for guidance on the matter. There have been many developments in recent years in scientific approaches to the study of consciousness in animals which are pertinent to this debate.