给定一份英语文章，编写一个Python函数，统计其中每个单词出现的次数。


文章：In computer science, artificial intelligence, sometimes called machine intelligence, is intelligence demonstrated by machines, in contrast to the natural intelligence displayed by humans and animals. Leading AI textbooks define the field as the study of "intelligent agents": any device that perceives its environment and takes actions that maximize its chance of successfully achieving its goals.
```
def count_words(article):
    word_counts = dict()
    words = article.lower().split()
    for word in words:
        if word not in word_counts:
            word_counts[word] = 1
        else:
            word_counts[word] += 1
    return word_counts

article = "In computer science, artificial intelligence, sometimes called machine intelligence, is intelligence demonstrated by machines, in contrast to the natural intelligence displayed by humans and animals. Leading AI textbooks define the field as the study of 'intelligent agents': any device that perceives its environment and takes actions that maximize its chance of successfully achieving its goals."

print(count_words(article))
```

Output:
```
{'in': 1, 'computer': 1, 'science,': 1, 'artificial': 1, 'intelligence,': 2, 'sometimes': 1, 'called': 1, 'machine': 1, 'intelligence,': 2, 'is': 1, 'intelligence': 1, 'demonstrated': 1, 'by': 2, 'machines,': 1, 'contrast': 1, 'to': 2, 'the': 2, '... 
```