title: deviance() function returns odd value
body: <p>See the following example code: </p>
  
  <pre><code>library(lme4)
  M100 &lt;- glmer(vs ~ wt + (1|cyl), data=mtcars, family=binomial("logit"))
  deviance(M100)
  summary(M100)$AICtab["deviance"]
  </code></pre>
  
  <p>the deviance function returns 13.95 but reading the deviance from the model summary object returns 24.76. What's going on here?</p>