The VisionWorksTM MethodMakerTM Module

MethodMaker consists of a suite of psychophysical methods that not only control the presentation of stimuli, but also collect, organize, and analyze the results. MethodMaker is included in our Contrast-Sensitivity applications as well as all other psychophysical applications, including custom applications. MethodMaker is also part of our high-end development system in the form of a library of high-level C-functions. A single function call will bring up a menu of methods and the associated parameters

The Experiment Types

Discrimination

Absolute Threshold

Point of Subjective Equality

Identification

Same/Different

Detection

 The Methods

Method of Adjustment

Method of Constant Stimuli (single-interval, forced-choice, yes-no)

Staircase (forced-choice, up-down)

Maximum Likelihood Estimation (QUEST and ZEST for forced choice and yes-no)

Signal Detection (ROC curves from different confidence levels)

Features Common to all Methods

Interweaving conditions (except Method of Adjustment)

Reaction times automatically collected, accurate to less than one millisecond

Results automatically sent to log and summary files and a special data file suitable for analysis by statistical packages

Optional feedback

Trials may be subject-initiated or automatic

N-alternatives for forced choice

Trial-by-trial results maintained

 Selected Method of Constant Stimuli (MOCS) Features

Levels may be set by user or automatically within a range

Randomization-within-block option--define a block of trials within which each alternative gets presented the specified number of times

Data collected and summarized separately for each level of the stimulus

Probit analysis performed and ogive displayed on-screen

 Selected Staircase Features

Additive, multiplicative or log steps

Number of steps back after a mistake can be specified

Option to move a step only after n correct responses (permits Wetherill-Levitt staircase)

May jump an extra amount after consecutive errors to avoid being stuck too low

Large initial steps may be specified to be reduced at each reversal during initial practice period (permits quick threshold determination)

Graph of results is displayed on-screen, shows each reversal

Results include mean of reversals, standard deviation and standard error

Selected Quest / Zest Features

Results including threshold mean, mode, and confidence intervals are computed and printed. The user has control over the following parameters:

Slope of assumed psychometric function

Threshold Definition ( 51% to 99%)

Assumed probability of a mistaken keypress (keeps maximum likelihood function from being overly affected by occasional wrong answers at high stimulus levels)

Random jitter for selection of next value (keeps trial from being too predictable)

Standard Deviation of prior probability density function

Termination Rule (termination may be set to fixed number of trials or may keep going until a specified threshold confidence interval is reached)

Initial probability-density function may be either Gaussian (as in QUEST), or hyperbolic secant (as in ZEST)

Use of mode (as in QUEST) or Mean (as in ZEST) to determine placement of next trial

Selected Signal Detection Features

Specify number of confidence levels and trials per level

d' values are computed and printed for each confidence level for each stimulus level

ROC curves printed on-screen for each stimulus level

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