Listen to true/false arguments AS3

I am making a small project in AS3 (FlashDevelop) to catch a JSON file which contains the following:

"properties" : [ 
    {
        "statement1" : true
    }, 
    {
        "statement2" : true
    }, 
    {
        "statement3" : true
    }, 
    {
        "statement4" : false
    }, 
    {
        "statement5" : true
    }, 
    {
        "statement6" : false
    }
],

Within my AS3 code I am monitoring it like this:

if (this.sessionController.currentSession.visitor.properties.statement4 == true) {
            _counterStatements=+1;
        }
        else {
            _counterStatements=-1;
        }

Is there an more easy/shorter way to do this? It seems like I am just outputting useless code now.

Many thanks in advance.

Greetings,

Bram

ps. I want to count the true/false arguments