Differences in standard deviation models the shape of the distribution. Although the distribution remains symmetric, the distribution becomes flatter if we increase the standard deviation. This corresponds to more diversity between the observations. In the animation we change the standard deviation of the normal distribution from 2.5 to 1, whereas the mean is not changed. Thus, because the standard deviation is a measure of variation, the differences between the values of the distribution decreases. Although the range of values in the movie differs dramatically, changes in standard deviation do not affect the mean, and changes in the mean do not affect the standard deviation.