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 |
• Feedback |