Table 1.

Properties of the sequential sampling models with and without boundaries.

		Primacy	Recency	Optimality	TC paradigm	IC paradigm
DDM	Unbound	–	–	Optimal	✓	✓
	Absorbing	✓	–	–	✓	✓
	Reflecting	–	✓	–	✓	–
OU	Unbound	λ > 0	λ < 0	λ = 0	✓	✓
	Absorbing	Various	λ < 0	λ < 0	✓	✓
	Reflecting	λ > 0	Various	λ > 0	✓	–
LCA	Unbound	w > k	w < k	k = w	✓	✓
	Lower-bound	w > k	w < k	Unknown	✓	✓
	Absorbing	Unknown	Unknown	w < k	✓	✓
	Reflecting	Unknown	Unknown	w > k	✓	–

The lower-bound LCA model refers to the LCA model that has only lower reflecting boundary at zero but no upper boundary.