The phrase "puts on thinking cap" is often used to describe the act of deep, focused thinking or problem-solving. However, there are many antonyms, or opposite expressions, that could be used to describe the opposite of this state of mind. For example, "switches off brain" or "zoned out" both describe a lack of focus or attention. Similarly, "lackadaisical" or "careless" suggest a lack of effort or dedication. Alternately, "spontaneous" or "intuitive" imply a more relaxed, creative mindset. Ultimately, the antonyms for "puts on thinking cap" suggest a range of mental states, from complete disengagement to free-flowing creativity.