"Basal" age is related to which measurement from the following?

In graded intelligence-testing scales (the Binet–Simon / Stanford–Binet approach), test items are arranged by age level. A test-taker's basal age is the highest age level at which every item is passed — it is the anchor point from which scoring proceeds, used together with the ceiling age (the level at which items start failing) to compute the person's mental age.

For this item, since basal age is read directly off performance on a graded ability scale, it feeds into the calculation of mental age and, relative to chronological age, the intelligence quotient. That is the measurement basal age is tied to.

Why the other options do not fit:

• Interest — describes what a person likes to engage with; it comes from preference/interest inventories, not from the age level at which graded test items are passed.

• Personality — covers stable traits and behavioural patterns, measured through separate personality assessments, not through a graded ability scale's starting point.

• Attention — reflects momentary focus/concentration, assessed with distinct attention tasks, not with the basal-age scoring anchor.

Basal age is therefore the measurement associated with intelligence.