Table 3. Stimuli of reaction time experiment. The rows show the different category pairings that defined the two response options (order of columns is arbitrary). At the top of each cell the colour name is shown with the overall number of stimuli in parentheses. The different kinds of objects are listed separately (natural, artificial, or novel objects), followed by the number of the respective objects in this category. In parentheses behind this number, objects are further specified as follows. In the sample of artificial objects: obj = object (represents itself), sgn = sign (nonlinguistic symbol), lg = logo (written label); in the sample of natural objects: ph = natural photos, den = ‘denaturalised’ (without natural texture), out = outline shapes, cart = cartoons (clip-art drawings).

Category 1	Category 2
BLUE (26)	BROWN (25)
Artificial: 11 (2 obj, 4 sgn, 5 lg)	Artificial: 6 (6 obj)
Natural: 15 (4 ph, 3 den, 4 out, 4 cart)	Natural: 19 (7 ph, 3 den, 3 out, 6 cart)
YELLOW (26)	RED (26)
Artificial: 10 (6 obj, 2 sgn, 2 lg)	Artificial: 11 (5 obj, 5 sgn, 1 lg)
Natural: 15 (4 ph, 4 den, 3 out, 4 cart)	Natural: 15 (4 ph, 3 den, 3 out, 4 cart)
Novel: 1 (Pompon)
GREEN (26)	ORANGE (22)
Artificial: 9 (4 obj, 3 sgn, 2 lg)	Artificial: 9 (7 obj, 2 lg)
Natural: 17 (5 ph, 3 den, 5 out, 4 cart)	Natural: 13 (4 ph, 3 den, 3 out, 3 cart)
VIOLET (17)	GREY (14)
Artificial: 1 (Milko)	Artificial: 2 (2 obj)
Natural: 12 (3 ph, 3 den, 3 out, 5 cart)	Natural: 12 (3 ph, 3 den, 3 out, 3 cart)
PINK (16)	WHITE (19)
Artificial: 4 (2 obj, 2 lg)	Artificial: 2 (obj)
Natural: 12 (3 ph, 3 den, 3 out, 3 cart)	Natural: 17 (6 ph, 3 den, 3 out, 5 cart)
YELLOW EXAMPLES (5)	RED EXAMPLES (4)
Artificial: 2 (1 ph, 1 out)	Artificial: 2 (1 ph, 1 out)
Natural: 2 (1 ph, 1 out)	Natural: 2 (1 cart, 1 out)
Novel: 1 (pompon)