hh.cen <- as.numeric(scale(data$hh, scale = FALSE))

model.hh <- lm(attention.hh ~ hh.cen * condition, data = data)
summary(model.hh)

Coefficients:
              Estimate Std. Error t value Pr(>|t|)
(Intercept)        0.04309    3.83335   0.011    0.991
hh.cen             4.97842    7.80610   0.638    0.525
condition          4.70662    5.63801   0.835    0.406
hh.cen:condition -13.83022   11.06636  -1.250    0.215

hh.sqr <- hh * hh

sqr.model.hh <- lm(attention.hh ~ hh.sqr + hh.cen * condition, data = data)
    summary(sqr.model.hh)