A fascinating study completed by Sumner, DeAngelis, Hyatt, Goodman, and Kidd (2019) suggests that toddlers are more susceptible to the recency bias (making a choice based off of the most recently presented information) than adults (who are more susceptible to the primacy bias--making decisions based on the first information presented). The study consistently found that toddlers between the ages of 1-2 years old opted for the second option when given an "or" question 70.83% of the time. A sample question was, "Should Rori bring a backpack or a lunchbox to school?" This pattern of responding was also present when nonsense words were used. Interestingly, this result (second choice selecting) was only present for verbal responses. When the children were permitted to indicate their response by pointing, there wasn't a significant difference in choosing the first or second option. In addition, it appears the recency bias decreases with age. 3 and 4-year-olds didn't demonstrate such patterns. The authors suggest that limited working memory in toddlers may be the culprite behind such response patterns. Given limited capacity, the most recent choice may be the only one they can access at that point in time. This may explain the discrepancy in verbal versus pointing response patterns. Having a visual picture of choices allows the brain to free-up space, per say, as the choices are presented in front of child rather than having to rely on memory. So, the next time you're allowing your toddler exercise "free-choice," you can perhaps stack the deck in your favor by presenting your preferred choice last and formatting the question with an "or."
Reference: Sumner E, DeAngelis E, Hyatt M, Goodman N, Kidd C (2019) Cake or broccoli? Recency biases children’s verbal responses. PLOS ONE 14(6): e0217207. https://doi.org/10.1371/journal.pone.0217207