P D was calculated for each pair of shape parameters (ν 1, ν 2). Figure 4 shows 3D contour plots of the P D values versus (ν 1,ν 2 ), for a value of the global SCR of 15 dB.
The second experiment was designed in exactly the same way, but used a simpler discrimination task, in which 20 other participants were required to determine whether or not pairs of shapes they saw were the same or different colours.
Unlike AA stimuli, these pairs of shapes had neither any obvious a priori connections nor non-random shared features with each other (see Fig. 4).
Colour vision test For colour trials, 100 unique pairs of shapes (Fig. 1 c, d) were filled with the green and the blue that were identical in brightness ("Matching brightness of colour" section).
We trained chimpanzees to identify pairs of shapes either linked by an arbitrary learned association (arbitrary associative dependency) or a shared feature (same shape, feature- based dependency), and to recognize strings where items related to either of these ways occupied the first (leftmost) and the last (rightmost) item of the stimulus.
For a pair of two shapes, the shapes are treated as the longitudinal segments parallel to the line connecting centroids of the two shapes, and the R-histogram is composed of the length ratios of collinear longitudinal segments.
Steel pipe as a vertical link and two transverse pairs of Shape Memory Alloy (SMA) wires are used as energy dissipation and recentering components, respectively.
The distance between pairs of color feature vectors is computed by Euclidean distance, while distances between pairs of shape and texture feature vectors are computed by city-block distance.
Chan, Whitaker, and Newell (2008) investigated the effect of object presentation in a task where participants haptically explored objects that consisted of specific pairs of shape and motion.
A pair of 2D/3D shapes is compared by measuring the amount of deformation required to register the shapes exactly.
