private function getDefaultNormalizer()
    {
        $default = $this->getDefault();
        $regex = $this->trueAnswerRegex;

        return function ($answer) use ($default, $regex) {
            if (\is_bool($answer)) {
                return $answer;
            }

            $answerIsTrue = (bool) preg_match($regex, $answer);
            if (false === $default) {
                return $answer && $answerIsTrue;
            }

            return '' === $answer || $answerIsTrue;
        };
    }