This is the right posture to sit to meditate. The head, neck and backbone should be as straight as possible. The reason being that when they are aligned in a straight line, very little energy is used to maintain that posture. During meditation, you need as much energy as possible to concentrate. When very little energy is required to maintain your posture, your baseline state of consciousness (b-SoC) is maintained without exerting more effort. If you slant your body, or slouch your body, then you require more energy to sit. You may not be able to focus as well on meditation. Some people fall asleep during meditation because they use up too much energy even in their sitting posture. Try the straight posture and drop us a comment to tell us whether you like it.
Why posture is important in meditation:
Assuming the correct posture does not utilize up much energy. Consequently, the person reduces his sense of self-identity. The activities that stabilize the baseline state of consciousness reduce so much that the b-SoC is destabilized. All these work to reduce energy used and frees up the energy.