Which finding, if true, would most directly weaken critic's claim?

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Hypothesizing that lullabies, characterized by their slow tempos, are universally calming to infants, Constance M. Bainbridge and colleagues played a lullaby sung in the Scottish Gaelic language and a non-lullaby sung in the Seri language to a group of infants. The team found that the infants' heart rates decreased more during the lullaby than during the non-lullaby. Since a decrease in heart rate is associated with relaxation, the team concluded that the lullaby relaxed the infants. Noting that reduced heart rate can also be associated with increased attention, one critic argues that instead, the lullaby simply attracted the infants' attention. Bainbridge and colleagues also measured pupil size, as pupils typically become larger when a stimulus captures a person's attention.

Blinking, which indicates attention, was equally frequent whether infants were listening to the song in Scottish Gaelic or song in Seri.

Neither the Scottish Gaelic language nor the melody of the traditional Scots lullaby was familiar to infants in the study.

The infants' pupils were smaller when the infants were listening to lullabies than when they Were listening to non-lullabies.

Parents of infants in the study chose the lullaby over the non lullaby when asked which song by they would use to calm their child.

Blinking, which indicates attention, was equally frequent whether infants were listening to the song in Scottish Gaelic or the song in Seri.

The infants' pupils were smaller when the infants were listening to the lullaby than when they were listening to the non-lullaby.

Parents of infants in the study chose the lullaby over the non-lullaby when asked which song they would use to calm their child.