Stimuli and experimental design
The experiment consisted of 480 trials in which participants were
presented with four digits in a row. The numbers were presented on a
dark gray background and some of the digits were colored in pink, blue
or green while the rest were presented in light gray (e.g., participants
would see “3218” where “3” and “2” were green and “1” and “8” were
light gray). The stimuli were kept constant across all conditions, thus assuring
that therewas no perceptual variation amongst them. Participants
were required to name the numbers colored in pink, blue or green aloud;
the specifics of the naming task varying upon instruction. Participants
were asked to either name the colored digits individually (‘three, two’),
the quantity of colored digits and the digits that were colored (‘three
twos’), the color of the digit and the digits that were colored (‘green
twos’), the complex number that they formed (‘thirty-two’) or the complex
number and the units separately (‘thirty, two’) (Fig. 1). The quantity
of colored digits and their location on the number varied in a controlled
fashion between conditions and all numbers were composed by four
digits to assure that participants could perceive all the digits of each
number at one glance (Kaufman et al., 1949; Saltzman and Gamer, 1948).