Statistical analysis
The gathered data were analysed using Statistica (Statsoft, Inc. Tulsa,
OK) v.6.1. To analyse sociodemographic participants’ characteristics,
one-way ANOVAs considering the Group as independent variable were
performed on age, IQ, and years of education. Participant demographic
characteristics are showed in Table 1. Due to group differences in IQ
[46], IQ was entered as a covariate of no interest in all analyses.
Performance on the Eyes task was analysed using analysis of covariance
(ANCOVA) with Group as the between factor, reading the mind in the eyes
accuracy as the dependent variable, and IQ as covariate.
To assess performance on the eye-gaze cueing task, a two-way mixed
design analysis of covariance was conducted with the following
variables: 2 (Group: Bipolar vs Control) x 2 (Cue: Invalid, Valid).
Trials with reaction times (RTs) faster than 200 ms or slower than 1200
ms as well as incorrect responses were excluded from the RTs analysis.
Mean RTs were computed for each experimental condition using the
remaining observations.