求翻译：Dr. Irene Pepperberg, a scientist at the University of Arizona, has worked with Alex for nineteen years. Teaching Alex to speak and understand wasn't easy at first.He had to learn one word at a time. Irene and an assistant(助手) would teach Alex by showing him what a word meant. Irene would hold up an object, saying "What's this?" Her assistant would give the word-"candy", for example-while Alex watched. Irene would praise(表扬) her assistant, then ask Alex the name for the object. When he got it right, Irene would praise him and give him the object to play with as a reward. It took Alex many weeks to learn his first word. After that, each new word became easier and easier for him.是什么意思？

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