teach an old dog new tricks—is used to say that old people can hardly be expected to learn anything new:
- This computer is far too difficult for me. You can’t teach an old dog new tricks.
Note:
a) The expression does not correlate in meaning with the phrase teach a pig to play the piano—do futile work attempting to deal with smb. who is absolutely hopeless:
- Teaching them democracy? It would be easier to teach a pig to play the piano.
b) The expression does not correlate in meaning with the phrase be an old dog at something—(Austral. sl.) be skilled at or well versed in smth. due to a long association with it:
- What I didn’t know was that Chicago attorney was an old dog at the game of cross-examination. He was in his elements.
teach one’s grandmother to suck eggs—is used as a caution against offering advice to others who are more experienced:
- There are people who know much more about this, but at the risk of trying to teach my grandmother to suck eggs, I will make the following observations.