public function watch2OnHighest(Decisions $decisions)
    {
        $literals = $this->rule->getLiterals();

        // if there are only 2 elements, both are being watched anyway
        if (count($literals) < 3) {
            return;
        }

        $watchLevel = 0;

        foreach ($literals as $literal) {
            $level = $decisions->decisionLevel($literal);

            if ($level > $watchLevel) {
                $this->watch2 = $literal;
                $watchLevel = $level;
            }
        }
    }