Why does he bet small on the turn? Did the Q scared him or is he slow playing AK? How much to bet here?

iPoker No-Limit Hold'em, $0.20 BB (8 handed) - iPoker Converter Tool from FlopTurnRiver.com

UTG+1 ($14.52)
MP1 ($3.70)
MP2 ($3.80)
CO ($21.68)
Button ($18.94)
SB ($19.29)
BB ($19.70)
Hero (UTG) ($10.82)

Preflop: Hero is UTG with ,
Hero calls $0.20, 4 folds, Button raises to $0.80, 2 folds, Hero calls $0.60

Flop: ($1.90) , , (2 players)
Hero checks, Button bets $1.90, Hero calls $1.90

Turn: ($5.70) (2 players)
Hero checks, Button bets $1, Hero ??