Which method involves giving an individual simultaneous access to multiple stimuli to assess preference?

The method that involves giving an individual simultaneous access to multiple stimuli to assess preference is known as engagement-based assessment. This approach allows practitioners to present various items or activities at the same time, enabling the individual to select what they are most interested in. By observing the selections made, practitioners can gather valuable data on preferences, which can inform treatment planning and interventions.

Engagement-based assessment is particularly beneficial because it reflects the individual's current interests and can lead to more effective reinforcement strategies. This type of assessment encourages active participation and helps ensure that the selected stimuli are genuinely preferred, as opposed to relying on individual items or observations in isolation.

Other methods listed, such as naturalistic observation and contrived observation, typically focus on observing behaviors in more generalized settings or structured environments without the direct manipulation of stimuli to gauge preference. Single-item assessment involves presenting one stimulus at a time to assess preference, which provides limited information compared to offering multiple options simultaneously. Thus, engagement-based assessment stands out as the most effective approach for eliciting preferences in this context.