Location discrimination.

A| Example psychometric functions for one subject on the location discrimination task for the hand, back, outer breast, and medial breast (including NAC). Negative values denote test points “below” the reference and the JND indicates the distance at which the subject could reliably (75% trials) locate the stimulus. B| Distribution of JNDs for each subject at each region. C| Relationship between the difference in size between the bust and underbust (Δ Bust) and the JND of the lateral breast. D| Relationship between the JND for the hand and breast across participants.

Spatial acuity of the nipple and areola.

A| Test locations for the quadrant discrimination task. The subject reported location using a number from 1 to 4 progressing clockwise from “above.” B| Proportion correct for participant at each test location. Solid markers indicate participants whose performance was significantly above chance (N=10). C| Relationship between breast size (bust – underbust) and performance on the quadrant task on the areola or nipple.

Absolute localization of contact events on the breast and back.

A| Example localization task data for the breast or B| back of one participant. Gray surface represents scanned torso. Black crosses indicate the true location of each stimulus, purple lines indicate the vector between the stimulus location and reported location, and blue lines indicate the vector between the stimulus location and average reported location across blocks. C| Reporting error (3D Euclidean distance) as a function of distance across participants for the breast and D| back. Error indicates mean error for each trial (mean of purple vector length in A,B), bias indicates the error of the average response (blue vectors in A,B), and imprecision is the mean pairwise error between individual responses for each point (distance between the end of purple vectors in A,B). E| The distribution of angles (2D, no depth axis) between the stimulus location and the reported location (gray) or the difference between said angle and the angle towards the relevant landmark (red) for the breast (nipple) and F| back (scapula).

Spatial acuity across regions

Relationship between the delta bust (bust – underbust) and the spatial acuity (JND) for the (A) hand, (B) back, and (C) medial breast. D-H Relationship between spatial acuity on all combinations of regions excluding that shown in Figure 1D.

Tactile localization performance of individual participants

A| Mean error for each participant across distances for the back and breast. Dashed line indicates unity. B| Example 2D responses to localization task for the breast of one participant and the C| back of another. Black crosses indicate the true location of each stimulus, purple lines indicate the vector between the stimulus location and reported location, and blue lines indicate the vector between the stimulus location and average reported location across blocks. D| Cartesian coordinate plot of Figure 3E (breast) where individual participants are represented by lighter colors. E| same as D but for Figure 3F (back). F| Unimodal vector strength of individual participants biases for breast and back. Dashed line indicates unity, dotted line indicates 95th percentile of vector strength from a simulated uniform distribution matched for the number of angles over which vector strength was computed after discretization (N = 11).