Numerical stroop effect

2 male and 2 female students from an undergraduate class in experimental psychology were participants in a numerical Stroop effect experiment. Mean age for the students was 19.5 yr., with a SD of 2.4. The Stroop effect was investigated with a numerical, as opposed to a color, task. The four conditions were Symbols (-, + + +, ===, ::, :::), versus Alphabetic Characters (C, AAA, DD, BBB, DDD), versus Matched Digits and Number of Digits (1, 4444, 333, 22, 4444), versus Mismatched Digits and Number of Digits (2, 1111, 444, 33, 3333). Participants took longer to count Mismatched Digits than Symbols or Alphabetic Characters (analogous to the color Stroop effect). Participants took longer to read Mismatched Digits than Alphabetic Characters (analogous to the color reverse Stroop effect). Participants took less time to read or count Matched Digits than Alphabetic Characters (facilitation effect).