diff --git a/packages/data/src/api.ts b/packages/data/src/api.ts
index e603b3be..ae1d0672 100644
--- a/packages/data/src/api.ts
+++ b/packages/data/src/api.ts
@@ -1,7 +1,6 @@
 import {
   ApiPromise,
   Child,
-  PastSession,
   Response,
   ResponseAttrsUpdate,
   ResponseUpdate,
@@ -50,7 +49,7 @@ export const retrieveChild = () => {
  * @returns Promise containing list of all Past Session objects.
  */
 export const retrievePastSessions = (uuid: string) => {
-  return deposit(get<PastSession[]>(`past-sessions/${uuid}/`));
+  return deposit(get<Response[]>(`past-sessions/${uuid}/`));
 };
 
 /**
diff --git a/packages/data/src/error.ts b/packages/data/src/errors.ts
similarity index 100%
rename from packages/data/src/error.ts
rename to packages/data/src/errors.ts
diff --git a/packages/data/src/lookitS3.ts b/packages/data/src/lookitS3.ts
index 6f8c0753..f3efff81 100644
--- a/packages/data/src/lookitS3.ts
+++ b/packages/data/src/lookitS3.ts
@@ -4,7 +4,7 @@ import {
   S3Client,
   UploadPartCommand,
 } from "@aws-sdk/client-s3";
-import { AWSMissingAttrError, UploadPartError } from "./error";
+import { AWSMissingAttrError, UploadPartError } from "./errors";
 
 /** Provides functionality to upload videos incrementally to an AWS S3 Bucket. */
 class LookitS3 {
diff --git a/packages/data/src/types.ts b/packages/data/src/types.ts
index 2154876f..1f800d29 100644
--- a/packages/data/src/types.ts
+++ b/packages/data/src/types.ts
@@ -1,5 +1,3 @@
-import { DataCollection } from "jspsych";
-
 export type ApiPromise = Promise<Data<Attributes> | Data<Attributes>[]>;
 
 export type Relationship = {
@@ -55,10 +53,15 @@ export interface ChildAttrs extends Attributes {
   readonly pk?: number;
 }
 
-export interface PastSessionAttrs extends Attributes {
+export interface JsPsychExpData {
+  trial_index: number;
+  trial_type: string;
+}
+
+export interface ResponseAttrs extends Attributes {
   conditions?: Record<string, never>;
   global_event_timings?: Record<string, never>;
-  exp_data?: DataCollection[];
+  exp_data?: JsPsychExpData[];
   sequence?: string[];
   completed?: boolean;
   completed_consent_frame?: boolean;
@@ -104,17 +107,7 @@ export interface Child extends Data<ChildAttrs> {
   };
 }
 
-export interface PastSession extends Data<PastSessionAttrs> {
-  type: "past_sessions";
-  relationships: {
-    child: Relationship;
-    user: Relationship;
-    study: Relationship;
-    demographic_snapshot: Relationship;
-  };
-}
-
-export interface Response extends Data<PastSessionAttrs> {
+export interface Response extends Data<ResponseAttrs> {
   type: "responses";
   relationships: {
     child: Relationship;
@@ -131,17 +124,18 @@ export interface ResponseUpdate {
 }
 
 export interface ResponseAttrsUpdate {
-  exp_data?: DataCollection[];
+  exp_data?: JsPsychExpData[];
   completed?: boolean;
   survey_consent?: boolean;
   completed_consent_frame?: boolean;
+  sequence?: string[];
 }
 
 export interface LookitWindow extends Window {
   chs: {
     study: Study;
     child: Child;
-    pastSessions: PastSession[];
+    pastSessions: Response[];
     response: Response;
     sessionRecorder: unknown;
   };
diff --git a/packages/lookit-initjspsych/src/errors.ts b/packages/lookit-initjspsych/src/errors.ts
new file mode 100644
index 00000000..449b887b
--- /dev/null
+++ b/packages/lookit-initjspsych/src/errors.ts
@@ -0,0 +1,8 @@
+/** Error when experiment data doesn't contain values on finish. */
+export class SequenceExpDataError extends Error {
+  /** Error when experiment data doesn't contain values on finish. */
+  public constructor() {
+    super("Experiment sequence or data missing.");
+    this.name = "SequenceExpDataError";
+  }
+}
diff --git a/packages/lookit-initjspsych/src/index.spec.ts b/packages/lookit-initjspsych/src/index.spec.ts
index a52ba060..9b8a1857 100644
--- a/packages/lookit-initjspsych/src/index.spec.ts
+++ b/packages/lookit-initjspsych/src/index.spec.ts
@@ -1,8 +1,17 @@
 import { JsPsych } from "jspsych";
 import lookitInitJsPsych from "./";
+import { Timeline } from "./types";
 
-const mockRun = jest.fn();
-jest.spyOn(JsPsych.prototype, "run").mockImplementation(mockRun);
+afterEach(() => {
+  jest.clearAllMocks();
+});
+
+/**
+ * Mocked chs data function used in testing below.
+ *
+ * @returns CHS experiment data.
+ */
+const chsData = () => ({ key: "value" });
 
 test("Does lookitInitJsPsych return an instance of jspsych?", () => {
   const jsPsych = lookitInitJsPsych("uuid-string");
@@ -14,7 +23,25 @@ test("Does lookitInitJsPsych return an instance of jspsych?", () => {
 });
 
 test("Is jspsych's run called?", async () => {
+  const mockRun = jest.fn();
+  jest.spyOn(JsPsych.prototype, "run").mockImplementation(mockRun);
   const jsPsych = lookitInitJsPsych("some id");
   await jsPsych({}).run([]);
   expect(mockRun).toHaveBeenCalledTimes(1);
 });
+
+test("Is experiment data injected into timeline w/o data?", async () => {
+  const jsPsych = lookitInitJsPsych("some id");
+  const t: Timeline[] = [{ type: { chsData } }];
+
+  await jsPsych({}).run(t);
+  expect(t[0].data).toMatchObject({ key: "value" });
+});
+
+test("Is experiment data injected into timeline w/ data?", async () => {
+  const jsPsych = lookitInitJsPsych("some id");
+  const t: Timeline[] = [{ type: { chsData }, data: { other: "data" } }];
+
+  await jsPsych({}).run(t);
+  expect(t[0].data).toMatchObject({ key: "value", other: "data" });
+});
diff --git a/packages/lookit-initjspsych/src/index.ts b/packages/lookit-initjspsych/src/index.ts
index 9188044c..ab2a17e6 100644
--- a/packages/lookit-initjspsych/src/index.ts
+++ b/packages/lookit-initjspsych/src/index.ts
@@ -1,7 +1,20 @@
 import { initJsPsych as origInitJsPsych } from "jspsych";
-import { JsPsychOptions } from "./types";
+import { JsPsychOptions, Timeline } from "./types";
 import { on_data_update, on_finish } from "./utils";
 
+/**
+ * Search timeline object for the method "chsData". When found, add to timeline
+ * data parameter. This will inject values into the experiment to be parsed chs
+ * after experiment has completed.
+ *
+ * @param t - Timeline object.
+ */
+const addChsData = (t: Timeline) => {
+  if (t.type.chsData) {
+    t.data = { ...t.data, ...t.type.chsData() };
+  }
+};
+
 /**
  * Function that returns a function to replace jsPsych's initJsPsych.
  *
@@ -26,6 +39,10 @@ const lookitInitJsPsych = (responseUuid: string) => {
      */
     jsPsych.run = function (timeline) {
       // check timeline here...
+      timeline.map((t: Timeline) => {
+        addChsData(t);
+      });
+
       return origJsPsychRun(timeline);
     };
 
diff --git a/packages/lookit-initjspsych/src/types.ts b/packages/lookit-initjspsych/src/types.ts
index ac2b409c..8e6271f2 100644
--- a/packages/lookit-initjspsych/src/types.ts
+++ b/packages/lookit-initjspsych/src/types.ts
@@ -1,17 +1,17 @@
+import { JsPsychExpData } from "@lookit/data/dist/types";
 import { DataCollection } from "jspsych";
 
-export type UserFunc = (data: DataCollection) => void;
+export type UserFuncOnDataUpdate = (data: JsPsychExpData) => void;
+export type UserFuncOnFinish = (data: DataCollection) => void;
 
-export type ResponseData = {
-  id: string;
-  type: "responses";
-  attributes: {
-    exp_data: DataCollection[];
-    completed?: boolean;
-  };
+export type JsPsychOptions = {
+  on_data_update?: UserFuncOnDataUpdate;
+  on_finish?: UserFuncOnFinish;
 };
 
-export type JsPsychOptions = {
-  on_data_update?: UserFunc;
-  on_finish?: UserFunc;
+export type Timeline = {
+  type: {
+    chsData?: () => object;
+  };
+  data?: object;
 };
diff --git a/packages/lookit-initjspsych/src/utils.spec.ts b/packages/lookit-initjspsych/src/utils.spec.ts
index 07890e2c..c40c066a 100644
--- a/packages/lookit-initjspsych/src/utils.spec.ts
+++ b/packages/lookit-initjspsych/src/utils.spec.ts
@@ -1,6 +1,7 @@
 import { DataCollection } from "jspsych";
 
-import { Child, PastSession, Study } from "@lookit/data/dist/types";
+import { Child, JsPsychExpData, Study } from "@lookit/data/dist/types";
+import { Timeline } from "./types";
 import { on_data_update, on_finish } from "./utils";
 
 delete global.window.location;
@@ -8,7 +9,11 @@ global.window = Object.create(window);
 global.window.location = { replace: jest.fn() };
 
 test("jsPsych's on_data_update with some exp_data", async () => {
-  const jsonData = { data: { attributes: { exp_data: ["some data"] } } };
+  const jsonData = {
+    data: {
+      attributes: { exp_data: ["some data"], sequence: ["0-first-trial"] },
+    },
+  };
   const response = {
     /**
      * Mocked json function used in API calls.
@@ -18,7 +23,7 @@ test("jsPsych's on_data_update with some exp_data", async () => {
     json: () => Promise.resolve(jsonData),
     ok: true,
   } as Response;
-  const data = {} as DataCollection;
+  const data = {} as JsPsychExpData;
 
   const userFn = jest.fn();
   global.fetch = jest.fn(() => Promise.resolve(response));
@@ -31,7 +36,9 @@ test("jsPsych's on_data_update with some exp_data", async () => {
 });
 
 test("jsPsych's on_data_update with no exp_data", async () => {
-  const jsonData = { data: { attributes: { exp_data: undefined } } };
+  const jsonData = {
+    data: { attributes: { exp_data: undefined, sequence: undefined } },
+  };
   const response = {
     /**
      * Mocked json function used in API calls.
@@ -41,7 +48,7 @@ test("jsPsych's on_data_update with no exp_data", async () => {
     json: () => Promise.resolve(jsonData),
     ok: true,
   } as Response;
-  const data = {} as DataCollection;
+  const data = {} as JsPsychExpData;
 
   const userFn = jest.fn();
   global.fetch = jest.fn(() => Promise.resolve(response));
@@ -54,12 +61,19 @@ test("jsPsych's on_data_update with no exp_data", async () => {
 });
 
 test("jsPsych's on_finish", async () => {
+  const exp_data = [{ key: "value" }];
   const jsonData = {
-    data: { attributes: { exp_data: {} } },
+    data: {
+      attributes: { exp_data, sequence: ["0-value"] },
+    },
   };
   const data = {
-    /** Mocked jsPsych Data Collection. */
-    values: () => {},
+    /**
+     * Mocked jsPsych Data Collection.
+     *
+     * @returns Exp data.
+     */
+    values: () => exp_data,
   } as DataCollection;
   const response = {
     /**
@@ -79,12 +93,96 @@ test("jsPsych's on_finish", async () => {
     chs: {
       study: { attributes: { exit_url: "exit url" } } as Study,
       child: {} as Child,
-      pastSessions: {} as PastSession[],
+      pastSessions: {} as Response[],
     },
   });
 
   expect(await on_finish("some id", userFn)(data)).toBeUndefined();
   expect(userFn).toHaveBeenCalledTimes(1);
-  expect(fetch).toHaveBeenCalledTimes(1);
-  expect(Request).toHaveBeenCalledTimes(1);
+  expect(fetch).toHaveBeenCalledTimes(2);
+  expect(Request).toHaveBeenCalledTimes(2);
+});
+
+test("Is an error thrown when experiment data is empty?", () => {
+  const exp_data: Timeline[] = [];
+  const jsonData = {
+    data: {
+      attributes: { exp_data, sequence: ["0-value"] },
+    },
+  };
+  const data = {
+    /**
+     * Mocked jsPsych Data Collection.
+     *
+     * @returns Exp data.
+     */
+    values: () => exp_data,
+  } as DataCollection;
+  const response = {
+    /**
+     * Mocked json function used in API calls.
+     *
+     * @returns Promise containing mocked json data.
+     */
+    json: () => Promise.resolve(jsonData),
+    ok: true,
+  } as Response;
+
+  const userFn = jest.fn();
+  global.fetch = jest.fn(() => Promise.resolve(response));
+  global.Request = jest.fn();
+
+  Object.assign(window, {
+    chs: {
+      study: { attributes: { exit_url: "exit url" } } as Study,
+      child: {} as Child,
+      pastSessions: {} as Response[],
+    },
+  });
+
+  expect(async () => {
+    await on_finish("some id", userFn)(data);
+  }).rejects.toThrow("Experiment sequence or data missing.");
+});
+
+test("Is an error thrown when experiment sequence is undefined?", () => {
+  const exp_data = [{ key: "value" }];
+  const jsonData = {
+    data: {
+      attributes: { exp_data, sequence: undefined },
+    },
+  };
+  const data = {
+    /**
+     * Mocked jsPsych Data Collection.
+     *
+     * @returns Exp data.
+     */
+    values: () => exp_data,
+  } as DataCollection;
+  const response = {
+    /**
+     * Mocked json function used in API calls.
+     *
+     * @returns Promise containing mocked json data.
+     */
+    json: () => Promise.resolve(jsonData),
+    ok: true,
+  } as Response;
+
+  const userFn = jest.fn();
+  global.fetch = jest.fn(() => Promise.resolve(response));
+  global.Request = jest.fn();
+
+  Object.assign(window, {
+    chs: {
+      study: { attributes: { exit_url: "exit url" } } as Study,
+      child: {} as Child,
+      pastSessions: {} as Response[],
+    },
+  });
+
+  expect(async () => {
+    await on_finish("some id", userFn)(data);
+  }).rejects.toThrow("Experiment sequence or data missing.");
 });
diff --git a/packages/lookit-initjspsych/src/utils.ts b/packages/lookit-initjspsych/src/utils.ts
index fbe0908e..7921bcb5 100644
--- a/packages/lookit-initjspsych/src/utils.ts
+++ b/packages/lookit-initjspsych/src/utils.ts
@@ -1,7 +1,8 @@
 import Api from "@lookit/data";
-import { LookitWindow } from "@lookit/data/dist/types";
+import { JsPsychExpData, LookitWindow } from "@lookit/data/dist/types";
 import { DataCollection } from "jspsych";
-import { UserFunc } from "./types";
+import { SequenceExpDataError } from "./errors";
+import { UserFuncOnDataUpdate, UserFuncOnFinish } from "./types";
 
 declare let window: LookitWindow;
 
@@ -16,13 +17,18 @@ declare let window: LookitWindow;
  * @param userFunc - "on data update" function provided by researcher.
  * @returns On data update function.
  */
-export const on_data_update = (responseUuid: string, userFunc?: UserFunc) => {
-  return async function (data: DataCollection) {
+export const on_data_update = (
+  responseUuid: string,
+  userFunc?: UserFuncOnDataUpdate,
+) => {
+  return async function (data: JsPsychExpData) {
     const { attributes } = await Api.retrieveResponse(responseUuid);
     const exp_data = attributes.exp_data ? attributes.exp_data : [];
+    const sequence = attributes.sequence ? attributes.sequence : [];
 
     await Api.updateResponse(responseUuid, {
       exp_data: [...exp_data, data],
+      sequence: [...sequence, `${data.trial_index}-${data.trial_type}`],
     });
     await Api.finish();
 
@@ -45,9 +51,23 @@ export const on_data_update = (responseUuid: string, userFunc?: UserFunc) => {
  * @param userFunc - "on finish" function provided by the researcher.
  * @returns On finish function.
  */
-export const on_finish = (responseUuid: string, userFunc?: UserFunc) => {
+export const on_finish = (
+  responseUuid: string,
+  userFunc?: UserFuncOnFinish,
+) => {
   return async function (data: DataCollection) {
+    const {
+      attributes: { sequence },
+    } = await Api.retrieveResponse(responseUuid);
+
+    const exp_data: JsPsychExpData[] = data.values();
+
+    if (!sequence || sequence.length === 0 || exp_data.length === 0) {
+      throw new SequenceExpDataError();
+    }
+
     const { exit_url } = window.chs.study.attributes;
+    const last_exp = exp_data[exp_data.length - 1];
 
     // Don't call the function if not defined by user.
     if (typeof userFunc === "function") {
@@ -56,7 +76,8 @@ export const on_finish = (responseUuid: string, userFunc?: UserFunc) => {
 
     await Api.finish();
     await Api.updateResponse(responseUuid, {
-      exp_data: data.values(),
+      exp_data,
+      sequence: [...sequence, `${last_exp.trial_index}-${last_exp.trial_type}`],
       completed: true,
     });
 
diff --git a/packages/surveys/src/consent.spec.ts b/packages/surveys/src/consent.spec.ts
new file mode 100644
index 00000000..0f85fc35
--- /dev/null
+++ b/packages/surveys/src/consent.spec.ts
@@ -0,0 +1,5 @@
+import { ConsentSurveyPlugin } from "./consent";
+
+test("Does consent survey return chsData correctly?", () => {
+  expect(ConsentSurveyPlugin.chsData()).toMatchObject({ chs_type: "consent" });
+});
diff --git a/packages/surveys/src/consent.ts b/packages/surveys/src/consent.ts
index 6c1d16ff..9c42349d 100644
--- a/packages/surveys/src/consent.ts
+++ b/packages/surveys/src/consent.ts
@@ -2,16 +2,12 @@ import SurveyPlugin from "@jspsych/plugin-survey";
 import { TrialType } from "jspsych";
 import { consentSurveyFunction } from "./utils";
 
-const info = <const>{
-  ...SurveyPlugin.info,
-};
-
-type Info = typeof info;
-export type Trial = TrialType<Info>;
+type Info = typeof SurveyPlugin.info;
+type Trial = TrialType<Info>;
 
 /** Consent Survey plugin extends jsPsych's Survey Plugin. */
 export class ConsentSurveyPlugin extends SurveyPlugin {
-  public static readonly info = info;
+  public static readonly info = SurveyPlugin.info;
   /**
    * Custom consent survey function adds functionality before creating a survey
    * based on the user-defined survey JSON/function.
@@ -25,4 +21,14 @@ export class ConsentSurveyPlugin extends SurveyPlugin {
       survey_function: consentSurveyFunction(trial.survey_function),
     });
   }
+  /**
+   * Add CHS type to experiment data. This will enable Lookit API to run the
+   * "consent" Frame Action Dispatcher method after the experiment has
+   * completed. It looks like jsPsych uses snake case for these data.
+   *
+   * @returns Object containing CHS type.
+   */
+  public static chsData() {
+    return { chs_type: "consent" };
+  }
 }
diff --git a/packages/surveys/src/exit.spec.ts b/packages/surveys/src/exit.spec.ts
index 4d64d583..7860f1d8 100644
--- a/packages/surveys/src/exit.spec.ts
+++ b/packages/surveys/src/exit.spec.ts
@@ -126,3 +126,7 @@ test("Is the withdrawal example included?", () => {
 
   expect(withdrawal?.choices[0].text).toContain("state secrets");
 });
+
+test("Does exit survey return chsData correctly?", () => {
+  expect(ExitSurveyPlugin.chsData()).toMatchObject({ chs_type: "exit" });
+});
diff --git a/packages/surveys/src/exit.ts b/packages/surveys/src/exit.ts
index 5ed31188..a9e834c1 100644
--- a/packages/surveys/src/exit.ts
+++ b/packages/surveys/src/exit.ts
@@ -47,7 +47,7 @@ export class ExitSurveyPlugin extends SurveyPlugin {
    * @param display_element - Display element.
    * @param trial - Info parameters.
    */
-  public trial(display_element: HTMLElement, trial: Trial) {
+  public trial(display_element: HTMLElement, trial: TrialType<Info>) {
     super.trial(display_element, {
       ...trial,
       survey_json: this.surveyParameters(trial),
@@ -146,4 +146,15 @@ export class ExitSurveyPlugin extends SurveyPlugin {
         ],
       });
   }
+
+  /**
+   * Add CHS type to experiment data. This will enable Lookit API to run the
+   * "exit" Frame Action Dispatcher method after the experiment has completed.
+   * It looks like jsPsych uses snake case for these data.
+   *
+   * @returns Object containing CHS type.
+   */
+  public static chsData() {
+    return { chs_type: "exit" };
+  }
 }