Always include the targeted keyword in the alt tag?

[nicole.healthline]

Studies show that using the targeted keyword in the alt tag helps to rank better for a keyword. But what if the keyword doesn't exactly describe the image, would you still use it in the alt tag?

For example, say you have an image of the brain, but the article is about cognitive behavioral therapy -- an accurate description would say 'human brain' but an SEO alt tag may say 'cognitive behavioral therapy'--which would you use?

[Bartell]

I would use alt tags to accurately describe the image. Google should be able to tell that an image of a human brain is closely related to cognitive behavioral therapy and will help add to the content and quality of the page. It might even look spammy to have "keyword stuffed" alt tags.

[NaHoku]

Wow, that's a really good question.  If there were only one image on a page (e.g. selling a product), I'm sure that labeling it as you suggest wouldn't get flagged as keyword stuffing.  Certainly you want to enrich the human experience, but to be honest, I haven't noticed as much impact with the alt tag as I have with other methods.  I'm interested to see how this discussion evolves.

[EGOL]

I usually try to make the first image on the page highly relevant to the primary keyword and use that keyword in the alt.  However, if the image was not well described by that keyword I would use something more appropriate.

It might help you with longtail and image search... but I doubt it will hurt much for the primary query... why not get a second image that matches the primary query?

[RobertFisher]

There is some good advice here from. Scott is right that your example is not inappropriate. EGOL is steering you very well also. 
When using alt text, most do not take advantage of what it can do for you. You can use around 140 characters and give a good description of the image (as if someone blind was hearing it) along with using keyword relevant text. I recently read that by having your images with good alt text get ranked in images that does have an effect on organic. Now, it wasn't Google saying it, but to a degree it makes sense it would have an effect - how much is anyone's guess.

If your example is not close to what you are putting up, go with EGOL's advice and get a new image. (I suggest geo tagging it if at all possible as well).

Hope this helps.