Moderators and Mediators of Perceptual Learning

Each trial starts with a fixation point (500ms) after which a Gabor (1° radius, at cut-off SF of 25% accuracy, estimated from Pre-Test CSF, at either 45° or 135°) appears for 128ms. The task is to indicate whether the Gabor was tilted left or right. Gabor contrast will be controlled by a 3/1 staircase (converging on approximately \~80% contrast threshold) across all training sessions.

Will be the same as the SPL with the exception that each session in LT will be twice as long as in SPL.

"Will be largely the same as SPL with the only difference being a change to the adaptive procedure. SS will use so-called short-staircases, which are initialized at 60% contrast with steps of .05 log units and employs a 3/1 staircase that after every 40 trials is reset (the short in short-staircases) back to 60% contrast."

This condition will be identical to SPL with the exception that two staircases - one a 2/1 staircase producing difficulties centered around 60-70% accuracy, the other a 4/1 staircase producing difficulties centered around 85-95% accuracy - will be utilized to control the stimuli.

The NT condition will be the same as SPL with the exception that contrast thresholds will be estimated in 5-different levels of external noise (10%, 15%, 20%, 25%, 30%).

TWF will be reasonably different from the standard SPL task. Here, on 50% of trials a target Gabor will be presented at either 45° or 135° (as in SPL) and will be flanked by two collinear Gabors. On the remaining 50% of trials, flankers will be present without a target. TWF is thus a yes/no detection task, which is necessary since the collinear flankers fully indicate the target orientation. In different 20-trial mini-blocks the flankers will appear either lambda, 1.5 lambda, or 2 lambda from the target (i.e., closer or further from the target) and target contrast will be controlled by a 3/1 staircase separately for each spacing.

The PT condition is the baseline for C8-C11 (all of which involve parafoveally presented targets). In PT, we utilize the same task as in SPL, however, in PT, in addition to central training, targets will also appear in one of two peripheral locations (5° eccentricity; angles = 135° and 270°). The location of targets will be randomized trial-wise so as to discourage eye-movements and independent 3/1 staircases will be run at each location. By training only 2 peripheral locations we can measure the extent to which training gives rise to location transfer (e.g., in transfer tasks examining performance at 8 different locations - 2 trained locations and 6 untrained locations). Furthermore, training at the central location facilitates comparisons between PT and SPL.

"The base task for SV is the PT condition. However, SV employ 20 trial mini-blocks of different SFs (.75, 1.5, 3, 6, 12, 24 cpd) and locations (45°, 135°, 225°, 315° - i.e., more locations than PT, but not the full set tested in the transfer battery) with separate staircases for each SF and location. Orientations will also be drawn from a larger set (22.5°, 45°, 67.5° - for which participants respond clockwise and 112.5°, 135°, 157.5° - for which participants respond counter-clockwise) and will vary on a trial-by-trial basis. This design holds-out 4 locations and 2 orientations to address transfer."

This is the same as C8, however we will use band-pass filtered stimuli similar to what has been done by a number of groups including Hussein et al.

Stimuli will be presented in a similar manner as in PT. However, in ExAT, a 100% valid cue, a small black dot - 48ms duration with an 96ms SOA prior to stimulus onset - will appear above the target location on each trial.

Stimuli will be presented in a similar manner as in PT. However, in EnAT, a 100% valid cue (letter UL, LR; standing for upper left and lower right, respectively) - 150ms duration with an 500ms SOA prior to stimulus onset - will appear at the fixation point.

MF utilizes the same basic task structure as in ExEAT, however, rather than a visual cue, an auditory cue will be used (50ms, 1000hz tone with sound location determined by convolving sound with generic head-related transfer function, kemar large ears.

"While not a training condition one type of experience that could be part of a condition is a no contact control (i.e., where participants do no training activities over the same rough time span as for the other training tasks)."