Absolutely. In modern JavaScript engines, for example, dynamic typing makes something as basic as |foo.bar = 7| extremely complicated internally. In SpiderMonke

Absolutely. In modern JavaScript engines, for example, dynamic typing makes something as basic as |foo.bar = 7| extremely complicated internally. In SpiderMonkey, |foo| could be a native object with |bar| in some varying location on a fixed or dynamic slot, or it could involve a proxy, a setter, unboxed or unboxed expando object, DOM or cross-compartment wrapper... To make the whole thing efficient, a particular property access could go through engine code, specialized JIT-generated native code after enough type information has been collected, or one of three inline cache systems, which generate multiple native code stubs |switch|ed on checks based on previous (slower) executions. A given get or set could even pass through more than one of the above, if too many checks fail and bailouts are required. And |bar| could be located directly on |foo| or on some object in |foo|'s prototype chain, requiring on-the-fly verification of additional invariants to ensure correctness. Static typing would mean the engine can know for sure what |foo| is and where to look for |bar|, allowing faster, guaranteed-correct code to be emitted ahead of time. Dynamic typing makes it harder to offer speed, correctness, security, and good memory usage all at once.