Context Matters: “Left Digit” Effects Can Arise for Digits That Are Not Leftmost

Number line estimation (NLE) tasks are widely employed in research and pedagogical contexts. For both children and adults, leftmost digits disproportionately influence number line placements-a phenomenon known as a left digit effect or left digit bias. Here, we ask whether left digit bias is limited to literal leftmost digits. In Study 1, adults completed a standard 0 to 1000 number line task and a leading zero version in which target numerals began with leftmost zeros (e.g., 0398). Study 2 used the leading zero task (placing numbers like 0398 on a range up to 1000) and a leading one-zero task (placing numbers like 10398 on a 10000-11000 number line). A robust "left digit" bias was observed for the hundreds digits in all cases, showing that left digit effects are deeply context-dependent. Task conditions can lead to strong left-digit-like biases for digits that are not the literal leftmost digits in the target numerals.