What cognitive bias involves giving more weight to the first piece of information in a sequence?

The anchoring effect is a cognitive bias where individuals rely heavily on the first piece of information they encounter when making decisions. This initial information acts as a "mental anchor" that influences subsequent judgments and evaluations. For example, if you first hear that a product normally costs $100 but is on sale for $70, the original price provides a reference point that shapes your perception of the sale price’s value. This can lead to decisions that are disproportionately influenced by that initial value, regardless of its actual relevance or utility in the context of the new information.

In contrast, the other options describe different cognitive biases. The base rate fallacy occurs when people ignore the statistical base rate of an event and instead focus on specific information, while the availability heuristic is about estimating the likelihood of events based on how easily instances come to mind. Illusory correlation refers to the perception of a relationship between two unrelated variables, which can distort our understanding of reality. Thus, the anchoring effect distinctly pertains to the weight assigned to the first information encountered, making it the correct answer.