Hi, I thought you may like this Mentalrobics exercise from Braingle.com:
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Giving Criticism

Nobody wants to hear all the things that are "wrong" with their idea. A bad criticizer uses any opportunity to make themselves feel smart or superior by pointing out everything that they think is bad about an idea. They take advantage of the fact that early ideas will inherently have many flaws and imperfections and they assume that they are in possession of the only "correct" idea.

Good criticism serves to give perspective and help the creator evolve the idea into a better solution. A good criticizer knows that early ideas will always have flaws. A good critic asks lots of questions to try to fully understand the situation before they give their feedback. Additionally, good feedback must avoid the use of negative energy. It is certainly possible to be very critical about an idea without using negative remarks that disrespect the creator and put this person on the defensive.

Instead of pointing out what is wrong, try to offer suggestions. For example, instead of saying, "That knob is way too big!" try saying, "Do you think a smaller knob would allow people with smaller hands to use it more comfortably?" Remember that what you dislike is not the same as what is bad. Try to keep personal opinions to yourself.

Another useful technique is to alternate positive and negative remarks. Point out something that is good for each thing that needs changing. For example, "This button is just the right size and shape, maybe we should think about adjusting the size of this knob to match it." It's like Mary Poppins sang, "A spoon full of sugar helps the medicine go down."
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For more mind exercises: http://www.braingle.com/mind/