Not from the Dictionary.
Responsibility – units of work that I have been assigned where there delivery rests on me, and perhaps my team, to complete by x point in time.
Accountability – work that is assigned to me where delivery rests on me, and again perhaps my team, to complete by x point in time wherein if said work is not completed by x point in time I will be the one that will have to explain the why, possibly with consequences built in.
One has a threat of consequence built into it, the other one implies ownership and freedom to deliver as one would see fit.
When we are responsible for work to be completed, we feel a sense of leadership and ownership emerge – “I want to do a good job, I want to proud of what our team delivers, I want to make this happen”. Having that sense of ownership and pride immediately makes us want to be more creative with our choices, reach out of the box and try something new. We have to get it done, but the path can go a number of different ways to get there.
When we are accountable, we swing more to the managerial side of the equation – “Okay guys, let’s do what needs to be done, not spinning globes or pretty sparkles and we all go home”. It doesn’t need to be something as far reaching as being fired or removed from that project, it could simply be a follow-up – “where did things go wrong? how come this didn’t happen?”. Who knows what it is, but you know if you don’t hit the x point in time, something, anything is coming your way.
People don’t deliver more or less when you tell them they are responsible or accountable. There is no proof.
If you want to grow a team, build leaders, experiment and encourage the creativity to fail and succeed, lean towards responsible. If you want very careful estimates, more predictability, less bells and whistles and perhaps the stifling of the creative cool, you’re already on the path to accountability.