What is the main idea of the passage?

Mantis shrimp have many specialized visual channels, but receptor count alone does not mean universally sharper color vision. (The passage contrasts receptor diversity with discrimination results and explains task-specific strengths.)

Why might direct color categories benefit a mantis shrimp?

They may support rapid recognition without extensive neural comparison among signals. (The third paragraph offers speed as a cautious functional interpretation of more direct channels.)

What does “discrimination” mean in the second paragraph?

the ability to tell similar stimuli apart (The laboratory task asks whether the animal distinguishes neighboring colors precisely.)

Which kind of light can some receptors detect?

ultraviolet light (The opening paragraph names ultraviolet sensitivity among mantis shrimp receptor classes.)

The Mantis Shrimp's Extra Colors: Level 4 Reading Comprehension Questions

Mantis shrimp have unusually complex eyes. Different species vary, but some possess many classes of photoreceptors, including receptors sensitive to ultraviolet light and to properties of polarization. Humans, by comparison, build most color vision from three classes of cone cells. It is tempting to conclude that the shrimp sees every color with extraordinary precision.

More receptor classes do not automatically mean finer color discrimination. In laboratory tasks, some mantis shrimp distinguish certain neighboring colors less precisely than humans do. Their visual system may classify wavelengths through relatively direct receptor channels instead of making extensive comparisons among a few overlapping signals.

That arrangement could favor speed. A quick category response may help an animal identify signals or objects without spending neural processing on tiny differences. This is a proposed functional interpretation, not a complete translation of the animal's subjective experience.

The eyes add other complexity. Each sits on a movable stalk, and specialized regions can sample different parts of a scene. Polarization sensitivity may support communication or detection in underwater environments. Those abilities should not be collapsed into a single ranking of “better vision.” Comparing species requires specifying the task. Humans may separate nearby hues well; a mantis shrimp may detect ultraviolet or polarization information that humans miss. Receptor count describes available channels, not a universal score for how richly or accurately an animal sees.

Comprehension questions