Dell, Burger, and Svec (1997) proposed that the proportion of speech errors classified as anticipations (e.g., "moot and mouth") can be predicted solely from the overall error rate, such that the greater the error rate, the lower the anticipatory proportion (AP) of errors. We report a study examining whether this effect applies to changes in error rates that occur developmentally and as a result of ageing. Speech errors were elicited from 8- and 11-year-old children, young adults, and older adults. The error rate decreased and the AP increased from children to young adults, but neither error rate nor AP differed significantly between young and older adults. In cases where fast speech resulted in a higher error rate than slow speech, the AP was lower. Thus, there was overall support for Dell et al.'s prediction from speech error data across the lifespan.