How our sensory/cognitive biases influence our study of visual modalities: Three tales of failure from the open sea

Sönke Johnsen

Biology Department

Duke University, Durham, NC

It has long been appreciated (and celebrated) that certain species have sensory capabilities that humans do not share, for example polarization, ultraviolet, and infrared vision. What is less appreciated, however, is that our position as land-bound human scientists can significantly affect our study of animal senses and signals, even within modalities that we do share. For example, our sharp vision can lead us to over-interpret the relevance of fine patterns in animals with coarser vision, and our Cartesian heritage as scientists can lead us to divide sensory modalities into separate parameters (e.g. hue and brightness for color vision), even though this division may not exist within the animal itself. This talk examines three cases from marine visual ecology where a reconsideration of our biases as sharp-eyed Cartesian land mammals can help address questions in visual ecology. The first case examines the enormous variation in visual acuity among animals with image-forming eyes and focuses on how acknowledging the typically poorer resolving power of animals can help us interpret the function of color patterns in cleaner shrimp and their client fish. The second case examines eye size and visual range in deep-sea cephalopods and shows that increasing pupil diameter is often far less advantageous in water than in air. The final case examines how the typical division of polarized light stimuli into angle and degree of polarization is problematic, and how a different interpretation is both closer to the physiological truth and resolves several issues, particularly when considering the propagation of polarized light through water.