how far does the analogy between echolocation and vision go?

Question

In popular culture and layman scientific explanations echolocation is often seen as a literal 'auditory version' of the visual sensory modality. Also perhaps given the human visual dominance, many of the technical terms too have visual flavours to them. e.g. Echolocators are thought to generate an 'auditory scene' after every sound emission (Moss & Surlykke 2010 ).

There are obvious differences in that auditory organs (ears/jaw bones/etc) don't automatically encode location - localisation occurs through explicit computation from time-differences and levels (Biosonar, Surlykke et. al. (Ed) 2014) . This is unlike the retina in the eye which already has explicit spatial encoding.

Given the general popular bias in treating echolocation almost like vision - what would you say is the strongest points where the two modalities differ?

PS: this question definitely doesn't have one answer, and perhaps also is not one to be encouraged in this SE? Looking fwd to see what the community decides...

Answer 1

I would first like to address

There are obvious differences in that auditory organs (ears/jaw bones/etc) don't automatically encode location - localisation occurs through explicit computation from time-differences and levels [ref]. This is unlike the retina in the eye which already have explicit spatial encoding.

Not sure if the retina can focus (estimate distance) at large distances (e.g. >10 m) but the OP means that an eye is like a planar array that allows the brain to find the direction of the object of interest by analysing the time-differences.

Vision is completely passive, so are ears when animals are listening. As passive systems, vision provide much more data to the brain than ears. So far so good, but echolocation is not a passive ranging method but an active one. Bio-sonar sound is highly directional and echolocating animals are typically scanning the world in front of them.

This is similar to using a pulsing narrow-beam flashlight in the dark. The brain is (or should be) capable to memorize (integrate) the returning light and to create a visual scene, especially, if that is the only information available. I have no reference to this, but this can easily be tested in night clubs when stoboscopes are used.

There are also indication in the echolocation click repetition rates (e.g. of sperm whales) that indicate that these animals choose only in the last moment a prey item. So one easily could conclude that all previous clicks are for obtaining an overview (i.e. generate an auditory scene)

Answer 2

I agree with and like WMXZ's answer, and would like to include that unlike vision, the relatively slow speed of sound there is a significant difference in echolocation. If the echo-locating animal is moving (ie, most of the time for a flying bat) then there is the aspect where the animal is swimming or flying through the various sound reflections returning to it. After studying bats for a number of years I subscribe to the 'complex spacial image' idea. They are clearly tracking a number of things at any given moment. I don't know if any research has looked at how they use Doppler shift to help calculate a pursuit path, but I suspect it is part of the soup.