Data Analyses

Dropout rates per session and age group were analyzed.

Infants who completed all three sessions were analyzed on the items of the feasibility questionnaire across sessions using repeated-measures ANOVAs to assess changes in stress. Pairwise comparisons using paired t tests with Bonferroni correction were conducted to determine which sessions significantly differ from each other. To assess systematic dropout, we divided the infant sample in completers and non-completers of session 1 and compared them on infant temperament and measures of socioeconomic status (SES) with t tests for independent samples.

To capture infant’s state who only participated in session 1, we divided the infant sample in completers and non-completers of session 1 and compared them on the items of the feasibility questionnaire with t tests for independent samples.

The data from infants, adolescents and adults was analyzed together. The data from all participants who completed acquisition was analyzed, regardless of whether or not they reached the TTC. To analyze if participants showed acquisition as a group, statistical analyses of CR were conducted as a repeated-measures ANOVA with block (8) as a within-subject factor. Pairwise comparisons using paired t tests with Bonferroni correction were conducted to determine which blocks significantly differ from each other.

Individual %CR in tone alone trials were analyzed.

To assess individual learning rates, TTC scores were analyzed.

To analyze if responsiveness to the air puff is related to conditionability, mean %UR was correlated to TTC and %CR in tone alone trials.

To study extinction, only the data from participants who showed successful acquisition as indicated by individual TTC scores was analyzed. To analyze if participants showed extinction as a group, statistical analyses of CR were conducted for eight blocks of extinction with a repeated-measures ANOVA. Pairwise comparisons using paired t tests with Bonferroni correction were conducted to determine which blocks significantly differ from each other. To analyze if participants generalized across the acquisition and extinction context, a paired t test on the CRs during the last acquisition block and the CRs during the first extinction block was conducted. A non-significant paired t test will suggest a complete generalization of acquisition (Vervliet et al., 2013).

To assess individual extinction learning rates, TTC scores were analyzed.