Omission neglect refers to insensitivity to missing or unknown information. Omission detection occurs once an omission reaches the threshold of awareness. Research in this area has demonstrated that consumers typically rely heavily on the information provided, and neglect omitted information, resulting in inappropriately extreme and confidently held judgments. Three experiments have been designed investigating the underlying processes of how consumers make inferences about omitted attributes. Two plausible explanations are investigated: anchoring and adjustment versus discounting. Adjustment refers to revising or updating an opinion, whereas discounting refers to not using information that is perceived to be non-diagnostic.
In Experiment 1, the underlying process is investigated using a point vs. range procedure. Salience of the omitted attribute is manipulated to elicit omission detection and participants are asked to provide either a point estimate or range estimates of the cost of the omitted attribute. Comparisons of the point and range estimates support an anchoring and adjustment explanation, but do not eliminate a discounting explanation. Experiment 2 further investigates the processing differences utilizing a cognitive load manipulation. The results suggest an anchoring and adjustment mechanism for people low in need for cognitive closure and a discounting mechanism for people high in need for cognitive closure.
Experiment 3 combines the two procedures used in Experiments 1 and 2 to more clearly differentiate the underlying process and investigates additional individual differences. The results suggests that people who are low in need for cognitive closure, people who are low self-monitors, and people who are high maximizers are more likely to utilize an anchoring and adjustment process. Conversely, people who are high in need for cognitive closure, people who are high self-monitors, and people who are low maximizers are more likely to be discounting. These experiments suggest that there are two possible underlying mechanisms for forming inferential judgments and that the type of mechanism used depends on individual trait differences and possibly situational variables. This research adds to the growing body of omission neglect research by helping to explain the underlying mechanisms in the formation of inferential judgments of omitted attribute information once an omission is detected.