Do Single-Blind Evaluations Measure Up?

A common method of research practice is the use of double-blind experimentation. This occurs when item identification is concealed in order to gauge an unbiased opinion, as in the case of a taste test. However, in psychology, assessing the progress of treatment cannot be done under double-blind conditions because the treating therapist and the patient are aware of the approach and issue being treated. Therefore, single-blind evaluations are made with the use of independent evaluators (IEs). These individuals are most often other therapists or students who rate the treatment progress by gauging symptom change and behavioral transformation. But does this unique method of assessment limit the measurement of psychological treatments? To answer this question, Adam B. Lewin of the Department of Pediatrics and Psychiatry at the University of South Florida’s College of Medicine recently conducted a study that compared IE’s ratings to those of therapists, clients, and parents using the Clinician’s Global Impressions (CGI) scale.

The participants were 71 children with obsessive compulsive disorder (OCD). They received 14 weeks of treatment, and evaluations were taken at four different points throughout. Lewin discovered that the IEs and the therapists provided similar ratings, even though the IEs had limited information and were not privy to in-session improvements. Additionally, the children and parents had similar ratings, but tended to rate the improvements more aggressively than the therapists and IEs. These findings are important for future research because they show that therapists’ ratings are in line with those of blind raters (IEs) and do not appear to be biased. This can be helpful in situations when blind evaluators are not available. Although the sample was relatively young, and the therapists were highly trained in OCD practices, the findings of this study have important implications for treatment measurement and future research efforts. “Our data suggest that blindness may not be essential for making accurate improvement ratings, provided that raters are well trained and efforts are made to minimize bias,” Lewin said.

Lewin, A. B., Peris, T. S., De Nadai, A. S., McCracken, J. T., Piacentini, J. (2012). Agreement between therapists, parents, patients, and independent evaluators on clinical improvement in pediatric obsessive-compulsive disorder. Journal of Consulting and Clinical Psychology. Advance online publication. doi: 10.1037/a0029991

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  • Oliver


    September 27th, 2012 at 3:33 PM

    Although it would appear that having an independent evaluator would be the ideal, when this is not available it appears that there is sufficient evidence to suggest that the therapist will not necessarily be biased and that it would be alright for him or her to evaluate when no other person is available.

    Hey that’s good enough for me.



    September 27th, 2012 at 9:18 PM

    Great to see these therapists were right on target with their assessments. Just gives so much more confidence to the clients that they are in the right hands and that the therapists knows how we the client is making progress. That is very important to modify treatment to ensure the best possible outcome.

  • rene


    September 27th, 2012 at 11:32 PM

    I don’t think it’s a good idea to gauge the precision I a professional by comparing with a student or an intern.Would be much better to always compare one professional with another.

  • joanne


    September 28th, 2012 at 3:58 AM

    If the therapist is well trained and willing to recognize his or her own flaws, then I don’t see why a study necessarily has to be double blind in nature. I realize that this has always been the ideal scientific situation, but we know that there are times when this is not possible. Sounds like with a well trained and objective counselor, this can be fine.

  • Keaton


    September 28th, 2012 at 5:18 AM

    Is there really a need of an independent evaluator? Because to me it seems like it is just doubting the expertise of a professional and then we are putting it to test. Two individuals may gauge the same thing differently, doesn’t mean either is wrong. And this has the chance of putting the professional under stress because he knows his evaluation is then going to be cross-checked against another!

  • Oskar


    September 28th, 2012 at 1:00 PM

    I don’t know- if there is no need for the independent evaluation, then why has this always been held up as the standard?

  • giselle


    September 28th, 2012 at 1:26 PM

    @Keaton:I think its always better to have more opinions and assessments when it comes to therapy. Therapy and its benefits often cannot be quantified and the only way would be assessments and results. So seeking a second opinion while ensuring the first is accurate does more good than harm. After all it is there for the benefit of the client ultimately!

  • Les


    September 29th, 2012 at 5:16 AM

    The parents and kids are probably being a little more optimistic regarding treatment improvements while therapists would remain a little more cautious. Therefore, this is a big point as to why it is good to continue with the idea that double blind studies are still the best. This way you have someone who is removed from the situation and can remain unbiased. It is far easier for someone so removed from treatment to do that versus someone who has been involved with the treatment since the very beginning.

  • nolan


    September 29th, 2012 at 6:01 PM

    is this a good thing? this a miracle and something to celebrate?no! the reason why their evaluations and ratings were similar because they were trained through the same courses and its like a reading,a measurement,no matter which meter you use,you get the same reading!

  • Mary b

    Mary b

    September 30th, 2012 at 4:59 AM

    I still think that when the situation is right then double blid is the way that you will receive the most fair and unbiased opinions.
    Even when we think that we are being objective, sometimes that can fail us.
    Often we have these inner discriminators that we are not even aware are at play!
    You take all of this away when the test is administered in a double blind fashion. There is no room for subjectivity when administered this way.

  • jordan


    September 30th, 2012 at 9:17 AM

    experience and expertise comes to the fore when judging something like whether the professional himself is evaluated or not if you can find one who is experienced and who you are comfortable with then that is all that matters…

  • leander


    September 30th, 2012 at 4:07 PM

    if the therapist is well trained and experienced then there is no need to doubt his rating.I believe this is a profession where experience comes to the fore and that a well trained eye will spot the changes immediately.anyway this is great news for all those seeking help of a therapist and the therapists in turn can be proud of this result.

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