Thanks for sharing.

Yes, I think it is acceptable with the proper reference in the text, as pointed out by Dr. Tarhini, in agreement with Prof. Bandyopadhyay.

You only have to acknowledge (in-text citation) the source of the instrument.

I would ask the author if I can contribute in some way to the study, what is the stage and what the author wishes to do.  Then I will collaborate rather than compete.   Would you like to collaborate on a project that is concerned about ethics and legitimate science and research?  Thanks.

https://www.researchgate.net/project/Navigating-the-challenges-of-predatory-publishing-for-the-sake-of-legitimate-science?_esc=profileProjectCardsNoStats&_sg=2iWkWThcI4j8AwcdySfJjC4mMFslgrgFegRNt_7NjqXxuczUSeW2DOEfcsiKDJ2r9NR8hukOf3UsV5-ogOb5Uw

There is no harm in learning to know how a available instrument works. However the validity of its results depends on the  strenuous iteration it had earlier gone through while testing. May be we can take inputs and customize, test and then validate it with the population of study to create a generalized or a rationalized scale evolution. 

Is it acceptable to use an instrument from a study that exists in the public domain?

For me before using the instrument & acknowledging it via in-text citation, I will also ask the original author for his / her approval to use even though the instrument is publicly available.  At the same time I will also ask the author for the instrument's reliability & validity from previous / other references etc.  If there is none, I will also ensure the instrument is reliable & valid by performing some tests etc.

I agree to Prof Ali Tarhini's view.

Han Ping Fung summarises the answer well.  At the end of the day, you don't 'have' to ask, but it is polite (& may even be helpful if they take an interest in your work). You do have to cite appropriately because it is not your own instrument, but as it is in the public domain, as long as you are adapting it for a different setting (i.e. you are not repeating the same study) & cite appropriately, then it is unlikely to be copyright protected unless stated by the originating authors (reasonable use).

Thanks for sharing.

Yes, I think it is acceptable with the proper reference in the text, as pointed out by Dr. Tarhini, in agreement with Prof. Bandyopadhyay.

And in agreement with Mr. Rowe.

You are not compelled to provide citation when using an item from the public domain. It is common practice in academia, however, to show respect for others by providing citation, even when using public domain material.

Regarding using images:

Images from royalty free clip art, such as the clip art available in Microsoft Word or Power Point, do not need to be cited. Works in the public domain technically do not need to be cited either, but doing so can help your readers find the original work so that they may better understand your references.

Please see the resources supporting  this viee at the links:

http://guides.temple.edu/c.php?g=77882&p=515489

http://libanswers.walsh.edu/mobile.php?action=5&qid=133674

One can use, if the author does not have any objection, and by citing the reference.

Behrouz - I would say that although you may not be compelled by law, you are compelled by the ethical conduct of our professional practices. Especially since the instrument in question is not clip art or a commercial image/product, then I would definitely regard citation as a must.

Dear Debra,

You may want to expand/change the term "an instrument from a study" in the title of your question.

I do not see any harm in citing the source. Contacting  the attorney can also open the doors for future collaborations. Here  is more info about how to cite a source available from public domain.

How to Cite a Psychological Test in APA Style

Here’s an example of a test you might have retrieved directly from a website:

Purring, A. (2012). Charisma and Tenacity Survey [Measurement instrument].

     Retrieved from http://www.apa.org/tests/measures/instruments/surveys

     /charisma.html

A test's name is a proper noun, so be sure to capitalize it in the reference.

In other cases, you may actually be citing the database record rather than the test. If you found a record for the test in a database, you can cite it, whether or not the record contains a link to the test itself:

Barks, H., & Howls, I. (2013). Directions of Generosity [Database record].

     Retrieved from The McAdoo Database of Fictional Titles. http://dx.doi.org

     /62.2366/34-28.466

Here is APA guidelines on how to cite an article found on public domain 

Article from Public Domain, E-journal and/or Nonaggregate Database NOTE: Full URLs are given with public domain e-journals, and/or non-aggregate databases where the URL will function in subsequent online sessions to retrieve the same article. There is no period at the end of a reference citation ending with a URL.

VandenBox, G., Knapp, S., & Doe, J. (2001). Role of reference elements in the selection of resources by psychology undergraduates. Journal of Bibliographic Research, 5, 117-123. Retrieved October 13, 2001, from http://jbr.org/articles.html

Jacobson, J. W., Mulick, J. A., & Schwartz, A. A. (1995). A history of facilitated communication: Science, pseudoscience, and antiscience. American Psychologist, 50, 750-765. Retrieved June 6, 2001, from http://www.apa.org/journals/jacobson.html

http://www.sjsu.edu/faculty/kathryn.blackmerreyes/guides/APAstyle.htm

http://blog.apastyle.org/apastyle/2014/02/how-to-cite-a-psychological-test-in-apa-style.html

Dear Nicholas,

"you are compelled by the ethical conduct of our professional practices"

I provided the links to support my post. Please do the same. As far as I know, we are not. If you  know of a reference that shows "not citing a source in public domain" is a breach of ethical conduct, please share it.I am willing to learn and  I appreciate it.

If I use a source from public domain,  I would provide the citation out of courtesy and respect for a colleague :)

Best regards,

Behrouz

Dear Behrouz, dear all, I used the instrument that was developed and validated by Prof Glynn, and I wrote to him, although permission was given in the article he published.  A questionnaire takes a lot of thought and time to develop, to validate and it's the least that I can do to inform the author, and thank him for it. I only did the reliability for my sample in this paper with Enzo. (This was the paper where I employed  Glynn et al. 2011.  Now I have placed a questionnaire on RG.  I hope to receive the same courtesy.  Thanks.)

Article Motivation and Achievement of Malaysian Students in Studying...

It is a matter of ethics to inform the author of instrument. Beside, citation of the sours is a MUST. What would happen if the author , when asked for, do not answer or answer negatively? What one do the next? I would not use the instrument of an autor without a permission. Completely different situation appears when author has passed away.

You have made an important question for us all, thank you, because each of us can or has become "victim"!

I agree with dear @ Ljubimir that responded you: "It is a matter of ethics to inform the author of instrument. Beside, citation of the sours is a MUST. What would happen if the author , when asked for, do not answer or answer negatively? What one do the next? I would not use the instrument of an autor without a permission. Completely different situation appears when author has passed away".

In biomedicine, you only need to cite the instrument if it is open-access. But it is nice to ask for permission or have cooperation with original authors. Some instruments are specific and not avaliable to everyone, as you need a licence to use them, for example psychological tests. 

You may use the instrument on condition that you give the credit to the author by clearly citing the author in your publication. It is just like using a histological staining method published by an author without taking prior permission, however you ought to cite the author of the staining method.

Ideally I would inform the original authors, but as long as you cite them and clearly explain your own usage, the instrument is in the public domain: it has been published for us to use and build on.  If a tool has been fully published (methodology, questions, analysis method etc.), then the concepts of publication 'fair use' guide that you can use it for a reasonable range of applications, as long as the original author is fully acknowledged. I am not sure how 'asking for permission to use the tool' works - I have seen it in various places, but I am not sure how legally binding this is, or even how ethical it is to make such a stipulation if the work has been made public.  If there is a patent on the tool or some other identified IP rights, then I can see formal permission being needed (especially if there is a commercial / non-academic interest), but for most study instruments, this is not the case.