Intonation

Ryutaro can apparently use three distinctive intonation patterns, accordingly: (1) flat/rising, (2) flat/falling, and (3) fall + rising.
The first one seems to be used when he needs attention, or to try to direct our attention to something. The second one is very unclear in terms of its function, but most frequently used with a pointing. The last one is used when he feels lonely or anxious, usually with this look of fear/anxiety, to perhaps ask for help/attention. Unless we respond accordingly, he gets upset or even cries.

By the way, the intonation patterns have been observed with "Papa" or "mama".