Median parameter estimates obtained by fitting to the bootstrapped pedestal masking data, with 95% confidence intervals.

<p>These values differ slightly from those in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150942#pone.0150942.t002" target="_blank">Table 2</a> as those were obtained by fitting to the empirical data.</p

Noise masking functions for our five observers.

<p>Median thresholds obtained from bootstrapping are plotted against the standard deviation of the masking noise, with error bars indicating the 95% confidence intervals. The curves show predictions from the LAM and NLM fitted to the median thresholds. The parameters for these fits are provided in Tables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150942#pone.0150942.t003" target="_blank">3</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150942#pone.0150942.t004" target="_blank">4</a>.</p

Parameters from LAM fits to simulated data from the nonlinear model (using the parameter populations presented in Fig 5) compared against the parameters (medians with 95% confidence intervals) obtained by fitting the bootstrapped empirical thresholds.

<p>Parameters from LAM fits to simulated data from the nonlinear model (using the parameter populations presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150942#pone.0150942.g005" target="_blank">Fig 5</a>) compared against the parameters (medians with 95% confidence intervals) obtained by fitting the bootstrapped empirical thresholds.</p

Example psychometric function (unmasked detection threshold for observer DB with binomial error bars) showing the fits from both the Weibull psychometric function and the CRF model.

<p>Each data point is labelled with the number of trials tested at that contrast level. The Weibull fit is made just to the data presented in this figure, whereas the CRF fit is made to the data from all mask levels simultaneously.</p

Parameters (in dB) obtained by fitting the LAM model to simulated nonlinear model (NLM) data, that were generated based on each observer’s dipper function.

<p>Standard errors provided are calculated from the bootstrap distributions. Predictions for these parameters are shown by the solid curves in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150942#pone.0150942.g006" target="_blank">Fig 6</a>. The mean across observers is reported with the standard error.</p

Efficiency of an observer who combines signals over multiple channels by picking the maximum, expressed relative to that of a linear ideal observer.

<p>We obtained by simulating the detection of various levels of signal (-42 to 36 dB in 3 dB steps) by independently noisy channels with different standard deviations (6 to 18 dB in 3 dB steps). We simulated 5,000 trials per combination of signal and noise level, both for a system where the outputs were summed (ideal) before comparison between the two intervals and for a system where the max() was taken. The data from this simulation were fit by a psychometric function (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150942#sec006" target="_blank">Methods</a>), and then the average efficiency of the max() observer was calculated relative to the ideal.</p

Median psychometric slopes obtained from bootstrapping plotted as a function of pedestal mask contrast for each observer.

<p>The error bars show 95% confidence intervals. As in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150942#pone.0150942.g003" target="_blank">Fig 3</a>, the curves show the predictions from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150942#pone.0150942.e021" target="_blank">Eq (11)</a>.</p

Parameters obtained by fitting the LAM model to the data for each observer, with the RMS error of the fit.

<p>Standard errors are calculated from the bootstrap distributions. Predictions for these parameters are shown by the dashed curves in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150942#pone.0150942.g006" target="_blank">Fig 6</a>. The mean across observers is reported with the standard error.</p

An example of the log-Gabor stimuli used in these experiments.

<p>The stimulus is shown within the fixation ring used to reduce uncertainty.</p