In discussion about rule-following and sceptical paradox, there is one solution called dispositional theory of meaning, which says, that if we are disposed to use a symbol + to denote addition, then it means addition. But what is disposition exactly?
In General, a behaviouristic approach to psychological entities wants to identify a specific mental event with a specific behavioural event. according to this, pain will be fully identified with the behaviour of being in pain: screaming "ouch", for example. Yet, sometimes we do not present the behaviour of pain while being in pain. To avoid this problem, behaviourists would say that pain is not the behaviour that is identified with being in pain, but the behavioural disposition of pain, or the behaviour identified with pain under normal conditions. A behavioural disposition, then, is the disposition to behave in a specific way under normal conditions. The meaning of the symbol "+" will be its use by a person under normal conditions, or in other words the behaviour of addition.