I’ve only ever had one dog that was smart enough for this to be an issue, and she was incredible. She had an impressive vocabulary of words she understood. She knew most of her toys by name. After she figured out that first spelled out word, probably O-U-T or R-I-D-E, it’s like she also understood the concept that we spell out words to disguise them from dogs so she’d pick up on each new variation of a word and spellings in short period of time. I eventually just stopped trying to stay ahead of her on that game.