Individual differences in intraperson variability in mood.

The experience sampling method and palm-top computers were used to obtain 75-100 randomly timed in situ assessments of 11 mood-related items from 54 Ss over 12-14 days. The variability in the distribution of an S's responses to each item was used as an estimate of intrasubject mood variability. Mood variability was stable across time (average r > .58) and across situations (average r = .51). The intercorrelations among the individual item variabilities were also substantial (average r = .41); when the items were combined into a mood variability scale, the coefficient alpha was .84. The stability and internal consistency of mood variability could not be reasonably attributed to similarity in item valences, differences among the Ss in the situations they encountered, response biases, or response errors. It was concluded that mood variability is a stable personal characteristic, but additional analyses suggested that it may be independent from other kinds of intraperson variability.