demos/Simulation_2stim_3psy_2resp_Watson(2017).html

<!DOCTYPE html>
<html>
    <head>
        <script src="../dist/jsQuestPlus.js"></script>
    </head>
<body>
    <p>This program simulates <a href="https://doi.org/10.1167/17.3.10">Watson (2017)'s</a> forth example: "Contrast sensitivity function {2, 3, 2}".</p>
    <p>Watson wrote that:</p>
    <blockquote>
    <p>In this example, we illustrate a case of multiple stimulus dimensions. 
    The example describes rapid estimation of a parametrically defined contrast sensitivity function. 
    Our approach is effectively the same as that of <a href="https://jov.arvojournals.org/article.aspx?articleid=2158170">Lesmes et al. (2010)</a> 
    except that we use a different model for the contrast sensitivity function. 
    Our main point is to show that their qCSF method can be easily accommodated into the QUEST+ framework. 
    </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>
</body>
<script>
    // Example: 2 stimulus parameters x 3 PF parameters 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(freq, contrast, threshold, c0, cf){
        const max = Math.max(threshold, c0 + cf*freq)
        return jsQuestPlus.weibull(contrast, max, 3, 0.5, 0.01)
    }

    // Psychometric function corresponding to the second response (response = 1).
    function func_resp1(freq, contrast, threshold, c0, cf){
        return 1 - func_resp0(freq, contrast, threshold, c0, cf) 
    }

    const spatial_frequency = jsQuestPlus.array(0, 2, 40) // [0, 2, 4, ..., 38, 40]
    const contrast = jsQuestPlus.array(-50, 2, 0) // [-50, -48, -46, ..., -2, 0]
    const threshold = jsQuestPlus.array(-50, 2, -30) // [-50, -48, -46, ..., -32, -30]
    const c0 = jsQuestPlus.array(-60, 2, -40) // [-60, -58, -56, ..., -42, -40]
    const cf = jsQuestPlus.array(0.8, 0.2, 1.6) // [0.8, 1, 1.2, 1.4, 1.6]

    // jsqp means jsQuestPlus. You can use any variable name you like.
    const jsqp = new jsQuestPlus({
        psych_func:  [func_resp0, func_resp1], 
        stim_samples: [spatial_frequency, contrast], 
        psych_samples: [threshold, c0, cf]
    })
    console.log(jsqp)

    // Note that the response is binominal.
    function simulate_observer(freq, contrast){
        const true_threshold = -35
        const true_c0 = -50
        const true_cf = 1.2

        if (Math.random() > func_resp0(freq, contrast, true_threshold, true_c0, true_cf)){
            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 stim = jsqp.getStimParams()
        const resp = simulate_observer(stim[0], stim[1]) 
        console.log(`Trial ${i+1}: Spatial frequency = ${stim[0]}; Contrast = ${stim[1]}; Response = ${resp}`)
        jsqp.update(stim, resp)
    }

    const estimates = jsqp.getEstimates()
    console.log(`Watson (2017) wrote the true threshold, C0, and Cf values as -35, -50, and 1.2, respectively.`)
    console.log(`jsQuestPlus estimates as follows:`)
    console.log(`Threshold estimate is ${estimates[0]}`)
    console.log(`C0 estimate is ${estimates[1]}`)
    console.log(`Cf estimate is ${estimates[2]}`)

</script>
</html>