fix #2462

.changeset/cuddly-mails-bathe.md

@@ -0,0 +1,5 @@
+---
+"@jspsych/plugin-instructions": patch
+---
+
+Fix simulation mode behavior so that setting RT and/or view_history correctly sets the other parameter

packages/plugin-instructions/src/index.spec.ts

@@ -104,4 +104,63 @@ describe("instructions plugin simulation", () => {
     expect(data.view_history.length).toBeGreaterThanOrEqual(6);
     expect(data.view_history[data.view_history.length - 1].page_index).toBe(5);
   });
+
+  test("Setting RT correctly sets the total length of the trial, #2462", async () => {
+    const timeline = [
+      {
+        type: instructions,
+        pages: ["page 1", "page 2", "page 3"],
+        simulation_options: {
+          data: {
+            rt: 4000,
+          },
+        },
+      },
+    ];
+
+    const { getData, expectFinished } = await simulateTimeline(timeline);
+
+    await expectFinished();
+
+    const data = getData().values()[0];
+
+    console.log(data.view_history);
+
+    expect(data.rt).toBe(4000);
+
+    let sum_view_history_rt = 0;
+    for (const view of data.view_history) {
+      sum_view_history_rt += view.viewing_time;
+    }
+
+    // this may not be exactly 4000 due to rounding errors
+
+    expect(Math.abs(sum_view_history_rt - 4000)).toBeLessThan(10);
+  });
+
+  test("Setting view history correctly sets the total RT, #2462", async () => {
+    const timeline = [
+      {
+        type: instructions,
+        pages: ["page 1", "page 2", "page 3"],
+        simulation_options: {
+          data: {
+            view_history: [
+              { page_index: 0, viewing_time: 1000 },
+              { page_index: 1, viewing_time: 1000 },
+              { page_index: 2, viewing_time: 1000 },
+            ],
+          },
+        },
+      },
+    ];
+
+    const { getData, expectFinished } = await simulateTimeline(timeline);
+
+    await expectFinished();
+
+    const data = getData().values()[0];
+
+    expect(data.rt).toBe(3000);
+  });
 });

packages/plugin-instructions/src/index.ts

@@ -258,23 +258,74 @@ class InstructionsPlugin implements JsPsychPlugin<Info> {
   private create_simulation_data(trial: TrialType<Info>, simulation_options) {
     let curr_page = 0;
     let rt = 0;
-    const view_history = [];
-
-    while (curr_page !== trial.pages.length) {
-      const view_time = this.jsPsych.randomization.sampleExGaussian(3000, 300, 1 / 300);
-      view_history.push({ page_index: curr_page, viewing_time: view_time });
-      rt += view_time;
-      if (curr_page == 0 || !trial.allow_backward) {
-        curr_page++;
-      } else {
-        if (this.jsPsych.randomization.sampleBernoulli(0.9) == 1) {
+    let view_history = [];
+
+    // if there is no view history and no RT, simulate a random walk through the pages
+    if (!simulation_options.data?.view_history && !simulation_options.data?.rt) {
+      while (curr_page !== trial.pages.length) {
+        const view_time = Math.round(
+          this.jsPsych.randomization.sampleExGaussian(3000, 300, 1 / 300)
+        );
+        view_history.push({ page_index: curr_page, viewing_time: view_time });
+        rt += view_time;
+        if (curr_page == 0 || !trial.allow_backward) {
           curr_page++;
         } else {
-          curr_page--;
+          if (this.jsPsych.randomization.sampleBernoulli(0.9) == 1) {
+            curr_page++;
+          } else {
+            curr_page--;
+          }
         }
       }
     }
 
+    // if there is an RT but no view history, simulate a random walk through the pages
+    // that ends on the final page when the RT is reached
+    if (!simulation_options.data?.view_history && simulation_options.data?.rt) {
+      rt = simulation_options.data.rt;
+      while (curr_page !== trial.pages.length) {
+        view_history.push({ page_index: curr_page, viewing_time: null });
+        if (curr_page == 0 || !trial.allow_backward) {
+          curr_page++;
+        } else {
+          if (this.jsPsych.randomization.sampleBernoulli(0.9) == 1) {
+            curr_page++;
+          } else {
+            curr_page--;
+          }
+        }
+      }
+      const avg_rt_per_page = simulation_options.data.rt / view_history.length;
+      let total_time = 0;
+      for (const page of view_history) {
+        const t = Math.round(
+          this.jsPsych.randomization.sampleExGaussian(
+            avg_rt_per_page,
+            avg_rt_per_page / 10,
+            1 / (avg_rt_per_page / 10)
+          )
+        );
+        page.viewing_time = t;
+        total_time += t;
+      }
+      const diff = simulation_options.data.rt - total_time;
+      // remove equal diff from each page
+      const diff_per_page = Math.round(diff / view_history.length);
+      for (const page of view_history) {
+        page.viewing_time += diff_per_page;
+      }
+    }
+
+    // if there is a view history but no RT, make the RT equal the sum of the view history
+    if (simulation_options.data?.view_history && !simulation_options.data?.rt) {
+      view_history = simulation_options.data.view_history;
+      rt = 0;
+      for (const page of simulation_options.data.view_history) {
+        rt += page.viewing_time;
+      }
+    }
+
     const default_data = {
       view_history: view_history,
       rt: rt,