Chroma meter cs150

We used 20 colours for encoding during the task. These colours were determined within a circle in the CIEL*C*h colour space, with a centre space at L* = 70, C* = 43, h = 62 and with a radius of 60 [35 (link)], such that all brightness and chroma values were common (L* = 70, C* = 103). The colour set included four colour-hue groups (orange, green, blue, and pink), each consisting of five colour phases equally spaced by 10 degrees. Furthermore, each colour-hue group was equally spaced by 90 degrees of hue angle on the CIEL*C*h circle. The precise colour settings in the CIEL*C*h colour space are summarised in the Supplementary Information (S1 Table). Participants did not know which colours would appear during each task before participation.
All visual stimuli were presented on a calibrated CRT display (MT852-12, Iiyama Corporation, Tokyo, Japan) using Psychtoolbox-3 [42 (link),43 (link)] programmed in Matlab (MathWorks, Inc. Natick, MA, USA). The monitor was calibrated once a month following standard methods [44 (link)] using a Chroma Meter (CS150, KONICA MINOLTA, INC. Tokyo, Japan). Each coloured square in the sample array subtended 1.7° × 1.7° of visual angle. Each square was centred 8.4° to the left, right, up, and down of fixation.

All visual stimuli were presented on a laptop computer screen (MacBook Pro 13-inch, Retina display, resolution 2,560 × 1,600) using Psychtoolbox-3 (Brainard, 1997 (link); Kleiner, Brainard & Pelli, 2007 ) programmed in MATLAB (MathWorks, Inc., Natick, MA, USA). The monitor was calibrated following standard methods (Brainard, Pelli & Robson, 2002 ) using a Chroma Meter (CS150; Konica Minolta, Inc., Tokyo, Japan). We placed the laptop computer display on a portable photography box measuring 60 × 60 cm to control the lightness of the environment (Fig. 1A). The backdrop was black and there was no light-emitting diode inside the box during the experiments.