“…The posterior collapse effect is a known problem of shallow VAEs when some or even all of the latent variables do not carry any information about the observed data. There are various methods to deal with this issue for VAEs, such as changing the parameterization [Dieng et al, 2019, He et al, 2019, changing the optimization or the objective [Alemi et al, 2018, Bowman et al, 2016, Fu et al, 2019, Havrylov and Titov, 2020, Razavi et al, 2019, or using hierarchical models [Child, 2021, Maaløe et al, 2017, Tomczak and Welling, 2018, Vahdat and Kautz, 2020b. Here, we focus entirely on the hierarchical VAEs since the posterior collapse problem is not fully analyzed in their context.…”