We sit beside each other, family, friends and pets, giving the impression of some shared experience. But we are different in how we perceive the world, and these external differences constrain and feed into vastly different internal representations and emotional states. As we journey through the world, through life, these forms of companionship are shaped by the consequences of these diverging experiences. To assume a selfish perspective of the world and expect that everyone around us perceives the same scene is understandable; it leads to the belief that only subjective opinion creates differences in preference or experience, but the reality is much more fundamental than that. Through both genetic and developmental variation, all living organism’s sensory systems are tuned slightly differently. These differences are most obvious when we compare species. Where dolphins can visualise echo-sounded radar, sharks sense the subtle electrical twitching of muscle fibres in their nearby prey and snakes see the thermal heat signature of a mouse dinner through sensors at the back of their mouths. Amongst the myriad ways in which we might perceive the visual world, the sense of instantaneous time is one of the most interesting for me as a zoologist, as it brings together philosophical questions about how the passing of time is experienced and how it puts constraints on the ways animals interact with one another.

The world around us proceeds across an infinite scale of detail and speed, from the ultra-fast beat of an insect’s wing to the nanometre growth of a tree, and we are aware of but a tiny window of this experience. This window constrains how we interact with the world, shutting off vast swathes of information and possibilities for interaction outside our narrow view. Animals vary enormously with regard to where they sit in this window of perception. Scientists have determined that the maximum speed at which the individual flickers of a flashing light can be perceived varies from as many as 250 per second in fast-moving flies to as low as a mere four per second for the inhabitants of the deep dark oceans as they struggle to capture what little light there is at all.

These constraints are best illustrated, however, not in the animal kingdom, but instead in experiments run on robots. Dario Floreano and Laurent Keller set up an arena in which small motorised robots were allowed to move around and associate with each other in simulated games of social interaction and predator-prey-like chases.[1] They allowed the robots to learn from their environment and evolve their own behaviours in order to optimise their actions for particular situations. They found that the robots only ever evolved to move at half of their top speed. The reason for this over-cautious behaviour was that their obstacle sensors only updated a few times a second and so if they moved any faster they risked crashing and failing. Animals are constrained in exactly the same way, but have the benefit of a much more complex system and millions of generations of evolutionary adaptations that allow them to push the boundaries of these constraints or find ingenious solutions to work around them.

One of my favourite of examples is the swordfish. A fast-moving predator in the open oceans, the swordfish often hunts squid and smaller fish in deeper cold waters. The swordfish’s trick is that it has a special heat-generating system in its muscles, eyes and brain that allows it to speed up the rates of chemical reactions that drive its sensory perception in tandem with its movement when it is hunting.[2] When these ‘cheetahs of the sea’ descend upon their prey they can have a visual system operating at speeds of more than ten times that of their cooler prey. It must be quite the harrowing experience to have something large and dangerous appear in your world operating at seemingly impossible speeds, far outside your perceptual comfort zone and adorned with a sword to add even more manoeuvrability and danger to the game, only to disappear again to the surface with a belly full of your shoal-mates. While these almost technological solutions are one way of pushing the boundaries of the constraints of perception, there are other ingenious ways to work around the problem. Some species of tiger beetles have effectively given up trying to see the world around them in real time.[3] Unlike the robots that opted to slow down when their perceptual limits were reached, the extremely fast tiger beetles just keep going, effectively running blind after their prey. They periodically stop, relocate their prey and charge off in their direction again, relying on speed to make up the ground they lose to this stop-start strategy. Other adaptations include running with their antenna slung over their head and just in front of their body, coupled with a reflex motor system that makes the beetle jump if the antenna bump into what is assumed to be a rock or other low obstacle in its path.

Similarly, their vicious-looking jaws are held open and literal hair-triggers line the inside so that when they do run blind into their prey, the jaws snap shut and the rows of spikey teeth ensure a tight hold of the prey.

It may be tempting to dwell on the life-and-death nature of predator-prey interactions but that is not the driver of the fastest visual systems. For that, we have to turn our attention to the other side of life and explore the role of reproduction. As an evolutionary force, there is nothing like the drive to reproduce to create extreme appearances and behaviours. If ever you see something in the animal kingdom that just seems excessive or pointless, it’s worth giving some thought to whether it might be the result of a runaway mate-selection process: the peacock’s tail, miniscule male anglerfish that effectively become symbiotic with the larger female, or the female spiders who cannibalise the male after mating. Mating is also the driver behind the fastest known visual frame rates of around 250 flashes per second that species of small blowfly are capable of perceiving.[4] Special areas of their compound eyes are devoted to detecting the high-speed dances of their would-be mates. Over evolutionary time, as the fastest and most accurate dancers were rewarded with mating opportunities, the females’ eyes become more and more attuned to the speed and accuracy of the dance, until they end up at the very limits of what is physically and chemically possible to perceive. There are many examples of these kinds of behaviour in the world, and yet they are effectively invisible to us and other animals. There are many worlds, and many existences going on under our very noses as information like this hides in plain sight, which has some profound philosophical consequences.

George Berkeley argued that ‘to exist is to be perceived.’ So inextricably linked are the two that our very being is tied to our window of perception and, in particular, the temporal niche it defines for us. It is no surprise that we have engineered a world that fits this niche and provides us comfort and security in our built environments. We drive at speeds that are comfortable for our reaction times, we have settled on an electricity format that causes flickers in our lights at the very upper end of our maximum perceptual threshold of around 60 flashes per second. An animal’s niche is the part of the environment where it thrives. All living things are highly adapted to their niches. To take them to the edges of these, or even outside them, will cause discomfort and stress. We know that as we fill our nights with artificial lights we are changing the way animals use our shared environment, and there is evidence that their visual frame rates, and possibly their predator-prey interactions, are affected by light pollution.[5] Put in situations outside our comfort zone, we start to experience either exhilaration, discomfort or fear arising from a sense of detachment between our perception and our ability to react to and control the events around us. We do this on purpose in sports and other thrill-seeking activities, but it can also be forced upon us through accident or attack. Regardless of the cause, much like the swordfish, we can’t operate at those high speeds for long and are constantly drawn back to our anchor of a safe, secure pace of life.

And so, as we sit beside our companion animals, it is worth considering that we are asking them to engage with a world designed for us. While the cat might be utterly indifferent to events with their own temporal niche being comparable to ours, the dog, who can perceive speeds up to 85 flashes per second, may well find aspects of our world jarring and unnatural. A visitor from another temporal niche to our own may pay no heed at all our environs, or possess a major advantage over us, or feel utterly out of place and uncomfortable. Perception is only one part of this story and one’s internal emotional response to it is equally important; as Berkeley noted, ‘That which is seen is one thing, that which is felt is another.’ Not only are we all wired differently in how we perceive the world, but we all have unique responses to the information we do receive. On person’s calm is another person’s discomfort. There is no ‘Us and Them’, rather ‘I’ and every other sentient being. If we take nothing else from that rather lonely perspective it perhaps should be a striving for empathy amidst a recognition that every animal, including us, sees and feels the world uniquely.

[1] Dario Floreano and Laurent Keller, “Evolution of Adaptive Behaviour in Robots by Means of Darwinian Selection,” PLoS Biologyvol. 8 no. 1 (January 2010), https://doi.org/10.1371/journal.pbio.1000292.

[2] Kerstin A. Fritsches, Richard W. Brill and Eric J. Warrant, “Warm Eyes Provide Superior Vision in Swordfishes,” Current Biologyvol. 15, no. 1 (January 2005): 55–58.

[3] Cole Gilbert, “Visual Control of Cursorial Prey Pursuit by Tiger Beetles (Cicindeli- dae),” Journal of Comparative Physiology A, vol. 181, no. 3 (1997): 217–230.

[4] Benjamin Tatler, David O’Carroll and Simon B. Laughlin, “Temperature and the Temporal Resolving Power of Fly Photoreceptors,” Journal of Comparative Physiology A vol. 186, no. 4 (April 2000): 399–407.

[5] Richard Inger, Jonathan Bennie, Thomas W. Davies and Kevin J. Gaston, “Potential Biological and Ecological Effects of Flickering Artificial Light,” PLoS One vol. 9, no. 5 (May 2014), https://doi.org/10.1371/journal.pone.0098631.

Dr Andrew Jackson is an Associate Professor in the School of Natural Sciences in Trinity College Dublin. He has an honours degree in zoology from Trinity College Dublin and a PhD in behavioural ecology from the University of Glasgow. His research focusses on the evolution and ecology of interactions between organisms and species. He enjoys taking a rather abstract view of these systems and primarily uses theoretical, computational and mathematical models to understand broad patterns in biology.