I would've liked to have seen Patricia Heaton's actual lovely, dark hair on the series. Nonetheless, she's a very pretty lady, and studying her is always worthwhile to me. So let's take a season-by-season look at Patricia in her wigs:

Season 1 - I like how the bangs sweep along, and the little flipping
of the ends of the hair. Great to see Patricia wearing earrings (it's a
shame when she is given a dowdy or even frumpy look) and rare to
see her ears on the series:
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Season 2 - This look would prove to endure. The bangs are straight
down to her eyebrows, and the straight hair ends curve gently inward:
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Season 3 - Not much has changed; nice to see an earring again:
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Season 4 - Here we see the overall length is a just little shorter. I like
how the bangs are still long enough to approach the corners of her eyes
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Season 5 - The hair is now much longer, breaking across Patricia's shoulders.
I think this long style is much more attractive than the previous looks:
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Continuing our look at Patricia over the seasons:

Season 6 - The length is now a little shorter than in the Season 5
image, but continuing to break across the shoulders. Unable to
obtain a front view to have a good look at Patricia:
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Season 7 - While apparently the same overall length, we see that
the bangs are easily among the longest ever seen on the series.
I like Patricia's necklace:
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Season 8 - The fullness is quite evident. The bangs are trimmed
straight across, around eyebrow length, and the overall long look
is pleasing:
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Season 8 once more - Within the same season, length can vary
somewhat. Patricia looks beautiful in profile:
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Season 9 - The bangs are now very full, nicely blunt-cut. This is
a fairly lovely look, with medium overall length complemented
by quite long bangs
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I so wish Patricia had things like more attractive outfits, more jewelry, and her own hair in beautiful styles on The Middle. But I realize her character called for more understated beauty, and I'm thankful lovely Patricia was cast in the series.