demos/Simulation_1stim_1psy_2resp_Watson(2017).html

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        <script src="../dist/jsQuestPlus.js"></script>
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    <p>This program simulates <a href="https://doi.org/10.1167/17.3.10">Watson (2017)'s</a> first example: "Estimation of contrast threshold {1, 1, 2}".</p>
    <p>Watson wrote that:</p>
    <blockquote>
        <p>The first is a very simple case in which there is a single stimulus dimension (contrast), and only a single psychometric parameter (threshold). This is the case for which the original QUEST was designed.</p>
    </blockquote>
    <p>Please open the JavaScript console window in your browser. If you are using Chrome on Windows, press Ctrl + Shift + I to open the console.</p>
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<script>
    // Example: 1 stimulus parameter x 1 PF parameter x 2 responses
    
    // Psychometric function corresponding to the first response (response = 0)
    // You can specify the function or use the weibull/normcdf function jsQuest provides.
    function func_resp0(stim, threshold, slope, guess, lapse) {
        // const tmp = slope * (stim - threshold)/20
        // return lapse - (guess + lapse -1)*Math.exp(-Math.pow(10, tmp))

        return jsQuestPlus.weibull(stim, threshold, slope, guess, lapse) 
    }

    // Psychometric function corresponding to the second response (response = 1).
    function func_resp1(stim, threshold, slope, guess, lapse) {
        return 1 - func_resp0(stim, threshold, slope, guess, lapse) 
    }

    const true_slope = 3.5
    const true_guess = 0.5
    const true_lapse = 0.02

    const contrast_samples = jsQuestPlus.linspace(-40, 0) // [-40, -39, -38, ..., -1, 0]
    const threshold_samples = jsQuestPlus.linspace(-40,0) // [-40, -39, -38, ..., -1, 0]
    const slope = [true_slope] // Don't forget to add brackets, i.e., specify as an array.
    const guess = [true_guess]
    const lapse = [true_lapse]

    // jsqp means jsQuestPlus. You can use any variable name you like.
    const jsqp = new jsQuestPlus({
        psych_func:  [func_resp0, func_resp1], 
        stim_samples: [contrast_samples], 
        psych_samples: [threshold_samples, slope, guess, lapse]
    })
    console.log(jsqp)

    // Note that the response is binominal.
    function simulate_observer(contrast){
        const true_threshold = -20

        if (Math.random() > func_resp0(contrast, true_threshold, true_slope, true_guess, true_lapse)){
            return 1 // yes
        } else {
            return 0 // no
        }
    }

    const nTrials = 32 // This is identical to that of Watson (2017)
    for (let i = 0; i < nTrials; i++){
        const contrast = jsqp.getStimParams()
        const resp = simulate_observer(contrast) 
        console.log(`Trial ${i+1}: Contrast = ${contrast}; Response = ${resp}`)
        jsqp.update(contrast, resp)
    }

    const estimates = jsqp.getEstimates()
    console.log(estimates)

    console.log(`Watson (2017) wrote the true threshold as -20.`)
    console.log(`jsQuestPlus estimates as ${estimates[0]}.`)
</script>
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