array not updating

components.some-component.js

import Ember from 'ember';
import { 
  times,
  constant
} from 'lodash';

const {
  get,
  set,
  Component,
  on,
  computed,
  A: EArray,
} = Ember;

export default Component.extend({
  answers: null,
  answerCheckedStates: null,

  onInit: on(`init`, function () {
    const lengthAmount = this.get(`answers.length`)
    const answerCheckedStates = times(lengthAmount, () => false)
    this.set(`answerCheckedStates`, answerCheckedStates)
  }),
  checkedStates: computed.mapBy('answers', 'checked'),
  actions: {
    toggleStatus(index) {
      const currentValue = get(this, `answerCheckedStates.${index}`)
      console.log(`Current value`, currentValue)
      set(this, `answerCheckedStates.${index}`, !currentValue)
      
      const answer = get(this, 'answers').objectAt(index);
      set(answer, 'checked', !currentValue);
      
      const changedValue = get(this, `answerCheckedStates.${index}`)
      console.log(`Changed value`, changedValue)
    }
  }
});

controllers.application.js

import Ember from 'ember';

const {
  A: EArray,
} = Ember;

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  answers: EArray([
    { id: 1, value: `Tomato`, checked: false },
    { id: 2, value: `Oranges`, checked: false },
    { id: 3, value: `Pineapple`, checked: false },
    { id: 4, value: `Sushi`, checked: false },                               
  ])
});

helpers.nth-child.js

import Ember from 'ember'

export function nthChild(params/*, hash*/) {
  return params[0][params[1]]
}

export default Ember.Helper.helper(nthChild)

templates.application.hbs

{{some-component
  answers=answers
}}

templates.components.some-component.hbs

{{#each-in answers as |index answer|}}
  {{#paper-checkbox
    value=(nthChild checkedStates index)
    onChange=(action "toggleStatus" index)
  }}
    {{answer.value}}
  {{/paper-checkbox}}
{{/each-in}}

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1",
    "ember-lodash": "4.17.4",
    "ember-paper": "1.0.0-alpha.19"
  }
}