Dilution in legal decision making: Effect of non-diagnostic information inrelation to amount of diagnostic evidence

Judgments about others are often based on information that varies in terms of its diagnosticity or usefulness in predicting a certain outcome. Previou s studies have demonstrated a "dilution effect" in which the addition of no ndiagnostic or irrelevant information yields less extreme judgments than th ose based solely on diagnostic information. Two studies investigated the di lution effect in a juror decision making context in which no midpoint of a scale was provided by researchers. Study 1 examined the inclusion of positi ve, negative, or neutral character information in a criminal case and found that this nondiagnostic information affected attitude toward the defendant but did not "dilute" guilt judgments. The cases in Study 1 contained a lar ger amount of diagnostic information than studies that demonstrated the dil ution effect. Thus, the amount of diagnostic evidence provided was varied i n Study 2, and the results showed "diluted" judgments only when a small amo unt of diagnostic information was presented. Limitations to the dilution ef fect were discussed.