Together with other aspects of what is referred to as 'executive function' (i.e. the ability to judge, initiate, plan, make decisions, and understand the feelings of others), changes in the ability to interact appropriately with other people are amongst the most troublesome aspects of dementia. They certainly can be amongst the most embarrassing. For example, saying to a stranger "You're fat! Why are you eating that ice-cream cone?" or asking a gathering of ladies who have visited to play bridge "I suppose you will want to start stripping soon?". These embarrassments are especially bad if they are completely out of character for the person with dementia.
When problems like this happen with any regularity, family members typically find that they no longer are able to rely on the person they care for. This is a difficult time, because it means that the disease has the upper hand.
One of the things that we have come to realize from treatment studies is that as bad as it is, having memory problems is not as bad as having poor judgment. Therefore, it is no surprise that family members particularly appreciate drug treatment if it results in improved judgment, even if memory improvement is less evident. Sometimes we find that using a class of anti-depressants known as 'Selective Serotonin Reuptake Inhibitors' - or SSRIs - also can result in improved judgment and getting along with others (what is often referred to as 'social conduct').
Problems with judgment are also especially sensitive to the environment in which they occur. For example, judgment is likely to be worse if the person feels under pressure, or is distracted by a noisy environment. Feeling like their judgment is being judged can be especially stressful - something that is no different from the rest of us.
Further Reading: The idea that impaired executive function, including problems with thinking and judgment, is the most troubling aspect of dementia is argued in detail in S Voss, R Bullock: 'Executive Function in Dementia' in K Rockwood, S Gauthier (eds) Trial Designs and Outcomes in Dementia Therapeutic Research. London: Taylor & Francis, 2005.