Interitem time distribution and response compatibility in the short-term serial retention of digits

Twenty digits were presented sequentially during a 40 sec display period. Three conditions of inter-item time distribution and three conditions of compatibility of answer sheet forms were employed in a 3 by 3 factorial design. The 20 digits were either distributed evenly over time, in two groups of 10 digits with a 20 sec rest between groups, or in three groups of 6, 7, and 7 digits with 10 sec rests between groups. Three levels of compatibility consisted of answer sheets containing either 20 equally spaced answer blanks, two groups of 10 blanks, or three groups of 6, 7, and 7 blanks. Results showed an interaction between the two variables. In addition, serial position curves showed multi-bowing effects which suggested both input and output anchoring.