This paper tests with an experiment on a minimum effort game Keynes’s conjectures that ‘animal spirits’ both affect decision making in the macroeconomy and that their influence is often more significant than that of rational calculation based on the facts. We do this by using a psychological theory of explanatory styles to spin news stories with the same facts either optimistically or pessimistically. In this way, the experiment also tests the power of ‘narratives’ to influence the macroeconomy. We find evidence to support both of Keynes’s conjectures and we draw policy insights that might flow from this test.