Assertion: The behavioural approach emphasizes the importance of observable and measurable data in understanding personality.

Reasoning: Behaviourists believe that personality can be best understood by studying the stimulus-response connections and their reinforcement. They view personality development as a change in response characteristics in relation to new environments and stimuli.

Both the assertion and reasoning are true, and the reasoning is a correct explanation of the assertion.

The assertion states that the behavioural approach gives importance to observable and measurable data in understanding personality. This is true because behaviourists focus on studying data that are definable, observable, and measurable. They believe that by observing and measuring responses to stimuli and environmental factors, they can gain insight into an individual's personality. The reasoning provides an explanation for the assertion. It states that behaviourists believe personality can be understood by studying stimulus-response connections and their reinforcement. They view personality development as a change in response characteristics based on new environments and stimuli. This reasoning aligns with the assertion and further supports the idea that the behavioural approach emphasizes observable and measurable aspects of behaviour in understanding personality.