意识研究仍然缺乏统一解释。心理学文献早在 1989 年就将意识描述为一种难以定义、难以解释其功能和进化原因的现象。Michael Pollan 的新书《A World Appears》共 320 页，梳理了关于意识的多种理论。学界目前存在 20 多种竞争性解释，其中许多围绕哲学家 David Chalmers 所称的“意识难题”，即为什么生物会产生主观体验。作者并未提出单一理论，而是系统介绍不同研究路径。
书中展示了一些非常规研究方向。例如部分科学家提出植物可能具有类似意识的机制。实验包括让玉米在金属迷宫中通过根系寻找肥料，或观察豆类植物寻找支撑物的生长行为。研究还发现麻醉剂不仅能关闭动物意识，也会影响植物行为，例如被麻醉的捕蝇草不会闭合叶片捕捉昆虫。这些实验试图探讨意识是否可能以不同形式存在于非动物生命中。
该书还讨论人工意识研究以及对意识体验的实验方法。Pollan 曾佩戴一种会在随机时间发出提示音的装置记录当时的主观体验，以研究意识内容，但发现记录本身可能改变思维。尽管研究持续增加，书中并未得出确定结论，因为意识本质上是主观体验，研究者无法进入他人头脑直接比较体验。因此现有理论仍然分散，从把意识视为信息处理，到认为它是生物在竞争需求间作出决策的机制。
Research on consciousness still lacks a unified explanation. As early as 1989, psychological literature described consciousness as a phenomenon difficult to define, explain functionally, or trace evolutionarily. Michael Pollan’s book A World Appears, spanning 320 pages, surveys numerous theories about the mind. Scholars currently propose more than two dozen competing explanations, many addressing what philosopher David Chalmers calls the “hard problem” of consciousness: why organisms have subjective experiences. Rather than presenting a single solution, the book reviews several major theoretical approaches.
The book also highlights unconventional research directions. Some scientists propose that plants might possess processes resembling consciousness. Experiments include placing corn plants in metal mazes to see how roots locate fertiliser or observing bean plants searching for poles to climb. Studies also show that anaesthetics affecting animal consciousness can alter plant behaviour; for example, a Venus flytrap exposed to anaesthetic will not close on insects. Such experiments attempt to explore whether forms of awareness could exist in non-animal life.
The work further examines efforts to create artificial consciousness and experimental methods for studying subjective experience. Pollan himself wore a device that emitted random signals prompting him to record his immediate mental state, yet the act of observation appeared to influence the experience being measured. Despite expanding research, the book reaches no definitive conclusions because consciousness is inherently subjective and researchers cannot directly access another person’s experience. Existing theories therefore remain diverse, ranging from viewing consciousness as information processing to describing it as a system for prioritising competing biological needs.