Laboratory experiments remain valid because subjects bring outside-world resources into them.

Evidence

Many have argued that such laboratory events are irrelevant to the investigation of human action in society. Indeed, some workers in this field have agreed with this view, and have retreated to a position where their only goal is the development of laws applicable to laboratory events (Rapoport 1970). Many of the criticisms are not without substance, but they do not lead to a necessary conclusion that anything which happens in the laboratory is completely unrelated to everyday life. Real events happen in the laboratory, and subjects deal with them using resources they have brought from the outside world. — Diego Gambetta, Trust - Making and Breaking Cooperative…, 551