First published in 1983. Psychological data are segments of life histories; as such they are ordered sequences of observations and by definition time series. Yet they are often anything but well behaved; what regularities and invariances they have are buried from all but the most persistent investigator. The most common methods of representing quantitative results in psychology are frozen outside time; thus they deliberately average out much of the sequential structure that holds any sparse clues to the nature of processes within the organism. This review, whose simple aim is to bring together in an illuminating juxtaposition on basic results in both time series analysis and in experimental psychology, thus. cuts across traditions within psychology.