The Bottle Optimization Testing Tiny Little Eaters Study

The researchers will study how babies respond to bottle nipples with different flow rates over a few days, and how this may affect how much milk they drink, their feeding patterns, and their sleep.

Inclusion Criteria: 1. Mother-infant dyad: The biological mother is the legal guardian of the infant and has custody for ≥5 days per week (in cases of joint custody). 2. Maternal age: Mother is ≥18 years old. 3. Language: Mother understands spoken and written English sufficiently to provide informed consent, answer questionnaires and follow study instructions. 4. Gestational age: Infant was born at 37.0-42.0 weeks gestation. 5. Birthweight: Infant's birthweight was appropriate for gestational age. 6. Bottle feeding: Infant currently receives at least one bottle feeding of ≥2 ounces at least once per week. 7. Residence: Family lives within approximately one hours driving distance of Ann Arbor, Michigan to participate in an at- home appointment or is willing to drive to the U-M North Campus research site. 8. Infant age: Infant is 4.0-6.0 months old at enrollment. Exclusion Criteria: 1. Current maternal depression or anxiety, as assessed by screening questionnaires, or any cognitive impairment that would limit ability to follow study instructions. 2. Infant developmental delay, genetic condition, or medical problems or diagnosis affecting current or future eating, growth, or development. 3. History of significant sucking or feeding difficulties or breastfeeding difficulties requiring significant medical intervention or support. 4. Current weight-for-age below the 10th percentile or significant history of poor weight gain. 5. Infant already typically uses a slower-flow nipple (flow rate \< 5 mL/min).