Figure 6

<p><u>Classification of ultrasonic vocalizations into distinct categories</u>. Representative sonograms and descriptive statistics for different types of USV that were emitted by (a–d) BALB and (a′–d′) B6 mice (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000351#s3" target="_blank">Results</a> for classification criteria). Descriptive statistics (mean±std. dev.) are given for the duration of each call type, as well as the beginning and ending dominant frequency. The USV traces are arbitrarily aligned to the 100-msec demarcation on the abscissa of each sonogram. Intensity changes within each representative vocalization are color-coded. (a″–d″) The production of each USV subtype was strain-dependent (* P<0.05, *** P<0.001 for BALB vs. B6 mice).