Radiolab – “Rippin’ the Rainbow an Even Newer One”
Date: March 15, 2018
Hosts: Jad Abumrad & Robert Krulwich

Episode Overview

This episode of Radiolab revisits a fascinating question first explored by the team seven years prior: "Who among Earth’s creatures sees the most spectacular rainbow?" Initially, they had crowned the mantis shrimp as the "champion of rainbows" for its reportedly incomparable color vision. Now, with new scientific insights, hosts Jad Abumrad and Robert Krulwich, along with expert guests, return to the subject to explore whether the mantis shrimp’s crown still fits—or if our understanding of color vision in animals needs to be updated.

Key Discussion Points & Insights

1. Recap: The Search for the Best Rainbow Viewer

• The Journey Begins
  (03:52) Jad and Robert revisit their earlier quest to find the animal with the richest perception of color, kicking off with Robert’s memorable interview question:

  "If a dog and a human and a crow were to be staring at a rainbow, would they be seeing very different things?"
  — Robert Krulwich (04:46)

• Comparing Animal Color Vision
  • Dogs: See a much narrower rainbow; lacking red-sensitive cones, dogs can only see blue, green, and some yellow. (05:52–06:13)

    "That's a sucky rainbow, dog."
    — Jad Abumrad (06:10)

  • Humans: With three types of photoreceptors (cones), we perceive around 100 color shades.
  • Birds (Sparrow): With ultraviolet perception and enhanced red sensitivity, their rainbow is broader at both ends of the spectrum. (07:31–08:06)
  • Butterflies: Boast 5–6 types of color receptors—more than humans, enabling more nuanced color distinctions. (08:28–09:09)
  • The Crown Goes To... The butterfly—until, underwater, the mantis shrimp enters the conversation.

2. The Mantis Shrimp: Myth and Reality

• Mantis Shrimp Visual System
  (09:36–11:29) Mantis shrimp were long believed to have an unmatched color vision arsenal:

  "Mantis shrimps have 16 kinds of receptors."
  — Tom Cronin (10:23)

  • Their eyes contain receptors for multiple bands of ultraviolet, visible, and infrared light, suggesting a “super-rainbow.”
  • They use their powerful claws not just for hunting but can even break aquarium walls.
• Crowning the Champion
  (11:48) The shrimp’s eye is twice as complex as any other animal’s—“no other animal that we know of has a visual system within 50% as complicated.”

  "You have a pugnacious Muhammad Ali seagoing animal with incredibly great visual synths."
  — Robert Krulwich (12:26)

3. Meeting the Champ (Firsthand Encounter)

• A Visit to the Mantis Shrimp
  (16:35–19:45) Jad visits Coney Island to meet a live mantis shrimp with expert Tom Cronin.
  • Their vivid color and aggressive behavior are on full display, including a dramatic predatory scene:

    "It launched out of its tube and then—just pow...that was just so sudden."
    — Jad Abumrad (20:08)

4. Science Advances: Rethinking Color Perception

• New Studies, New Questions
  (21:22–27:09) Marine biologist Justin Marshall, the pioneer in mantis shrimp vision research, recounts how his team discovered their color vision in the mid-90s.

  "She walked in, and the shrimps went wild."
  — Justin Marshall (22:11)

  • Do they use their complex eyes as we once thought?
    • The new data shows that although mantis shrimp possess a multitude of receptors, they are surprisingly poor at distinguishing between subtle shades of the same color—a task humans excel at.

    "It was the worst animal on the planet so far tested."
    — Justin Marshall on their color distinction abilities (24:46) "Our champion of the rainbow was the worst creature ever tested."
    — Jad Abumrad (25:02)

  • The mantis shrimp’s color vision is not about seeing a continuous dazzling rainbow. Their perception seems to be more like seeing distinct, non-overlapping color bands, with little blending or nuance between them.

5. What Is Color For? (Communication, Not Aesthetics)

• Color as Language
  (27:39–29:44) The vast repertoire of color perception in mantis shrimp may be more about communication than admiring rainbows.

  "Instead of seeing rainbows, they're having a conversation with the color."
  — Robert Krulwich (28:49)

  • Evidence suggests they use color—and even polarized light, which humans cannot perceive—as a vocabulary to communicate with each other, signaling things like fear, mating, or territory.

6. The Concept of "Umwelt"

• (30:17) The episode closes with a reflection on the concept of umwelt: the idea that each animal inhabits its unique perceptual world determined by its senses.

  "It's the word that says that you are limited by what you can feel, touch, smell, see."
  — Robert Krulwich (30:46)

  • The hosts muse about the limitations not just between species, but even between humans:

    "I have regular moments with my wife where I’m like, 'that’s not blue', and she’s like, 'yeah, it’s totally blue.'"
    — Jad Abumrad (31:10)

Memorable Quotes

• On Science’s Constant Revision:

  "We’re going to reevaluate that coronation right now, as one does as time passes and science advances."
  — Jad Abumrad (04:03)

• On Mantis Shrimp Seeing ‘Ecstatic’ Colors:

  "Their rainbow is more a series of rather focused, discreet bands of color with not a lot in between."
  — Jad Abumrad (27:16)

• On Animal Vision and Understanding:

  "You will never know what a bat knows when it echolates... Do they see more of something else? I don't know."
  — Robert Krulwich (30:17)

• On the Mystery of the Mantis Shrimp:

  “They are an unbelievably amazing and different system to any other animal on the planet. So you’ve got to ask yourself the question, why? ... So you could call me a failed biologist.”
  — Justin Marshall (29:20)

• On the Mantis Shrimp’s Unique Weirdness:

  "They're really fucking weird."
  — Justin Marshall (29:58)

Key Segment Timestamps

• [03:52] — Recap of previous episode; Robert asks: “Would a dog, human, and crow see a rainbow differently?”
• [05:53–08:53] — Discussion on animal rainbows: dog, human, sparrow, butterfly.
• [09:36–12:26] — Introduction to mantis shrimp and their supposed vision superpowers.
• [15:37–20:43] — Jad meets a live mantis shrimp and witnesses its ferocity.
• [21:22–25:07] — Justin Marshall discusses how mantis shrimp actually use their color vision and new discoveries.
• [27:39–29:20] — Communication as the main purpose of color perception in mantis shrimp.
• [30:17–31:22] — Reflection: The concept of umwelt and perceptual worlds across species (and humans).

Tone & Style

The episode is playful and inquisitive, with moments of awed wonder and humility in the face of scientific revision. There’s humor (designer clownfish, the pugnacious mantis), but also a genuine respect for the mysteries of animal perception—and for how much we don’t know.

Conclusion

Radiolab’s return to “Rippin’ the Rainbow” is less about unmasking a new champion and more about celebrating the evolving, ever-strange nature of science. Seven years on, the mantis shrimp is revealed as unique not for the breadth of its color vision, but for the alien way it uses it: not to see a wider rainbow, but perhaps to "speak" a language of color unimaginable to us. In the end, the show reminds us not only of the diversity of perception in the animal kingdom, but of the limits and possibilities in our efforts to understand it—even, sometimes, between ourselves.

Special Note

The episode is dedicated to Daniel Thompson, a choir member who contributed to the show and tragically passed away—a reminder, as Radiolab often provides, of the humanity behind curiosity and discovery.