Amazon.com announced a series of largely incremental refinements on Wednesday to several of its artificial intelligence products as it seeks to keep rivals at bay amid a continued investor frenzy over the technology. The retailer has sought to counter a perception that competitors Google, Microsoft and OpenAI have taken a lead in developing generative AI, which can respond almost instantaneously with full sentences or pictures to complicated prompts or queries. The improvements Amazon announced at its conference in New York include adding additional memory to so-called agents that automate work for businesses, so that each new request can build on prior ones, said Vasi Philomin, Amazon’s vice president of generative AI.