sensory ecology

Image: Tima Miroshnichenko


Unlike the world of things, the world of ideas is not open to direct examination by outside observers.

Is there a real world out there?

Yes, there is a real world out there. Treating the outside world as a real, objective entity, not a hallucination or a dream, is not only a prudent but also a healthy point of view. In addition to offering support to the work of scholars who continue to fight to unravel and understand what is happening around us, this point of view is already adopted by many people. It is, therefore, a good guiding principle, whether at the institutional level or at the psychological level.

Before proceeding, it is worth explaining the meaning that I adopt for certain terms. The use of the objective label, for example, stems from the fact that the existence of the world (and the countless elements that inhabit it) (i) is independent of the individual will of any one of us; and (ii) can (and should) be attested by third parties (read: other observers).

Yes. The veracity of the statement “There is a real world out there” is ultimately the result of a verdict. Which is to say that scientific claims about the world must be attested (and then maintained or refuted) by more than one observer. Which is not to say that what cannot be attested does not exist or has no chance of existing. It's just that science doesn't have much to say about such entities, at least current science.

In addition to a real and objective world out there, there is also a subjective world inside each of us... Yes, we can – and should – assume that there is an inner world inside each human brain. (Just as there is an inner world inside the brains of many other animals; a subject on which, however, we will not go into detail here.)

The inner world is the world of ideas. In relation to which, moreover, it would no longer be appropriate to apply the objective label. It's not hard to see why: Unlike the world of things, the world of ideas is not open to direct scrutiny by outside observers.

Understandably, therefore, the subjective world is something far more elusive and elusive. A world about which countless uncertainties proliferate, as well as myths and misunderstandings. The scientists themselves who deal with the subject are used to walking between doubts and inconsistencies. Many of which, it must be said, are quite intriguing.

Consider the following question: If the existence of an inner world cannot be directly attested, how can I be sure that other human beings are equally endowed with thinking minds? (I assume that I myself have one.)

As Dennett (1997, p. 9) noted: “Are we sure that all human beings have minds? Perhaps (considering the most extreme case of all) you are the only mind in the universe; perhaps all other things, including the apparent author of this book, are mere mindless machines. This strange idea first occurred to me when I was very young, and perhaps it has occurred to you too.”

In summary, ideas are immaterial entities, also said to be subjective. They populate a world whose existence, nature and dynamics can only be investigated indirectly.

The world as representation

There is a correspondence between the world of things and the world of ideas, even if it is not a completely symmetrical correspondence. There are at least two reasons to justify the asymmetry. First, because many objects in the outside world are not represented in our minds. Second, because many of the representations we carry with us are incomplete, imperfect or even distorted. Let us examine the matter a little more closely.

Our world – that is, the world in which each of us lives – is largely a representation, a map built inside our brains. It turns out that, in addition to being unreliable, such a representation is neither fixed nor immutable – we can change our minds about certain things.

It bears repeating: The map of the world that we carry with us has its stability, but it is not a definitive or immutable map. In fact, our mental map undergoes frequent daily adjustments, and may even be redesigned – perhaps even entirely redesigned, as is the desire and purpose of certain organizations that manipulate the mental plasticity of human beings (eg, opportunistic religious sects, such as the so-called neo-Pentecostal churches , and the secret service of some countries, such as the CIA, of the United States, and the Mossad, of Israel).

Part of this mental dynamic is due to the fact that the brain is receiving signals from the outside all the time. Such bombardment, in turn, is the result of an apparently inescapable reality: Our life is a contextualized experience. We can avoid coexistence with other human beings, but there will always be a context – after all, no human being is self-sufficient, no human being can live in an ecological vacuum.

In the midst of an incessant and apparently chaotic bombardment, our sense organs are in charge of selecting just a few signs of interest.

Sense organs as selective filters

The mediation between the brain and the outside world is done through specialized surfaces or structures – the sense organs.[1] These sensorial structures capture, filter and forward the received signals (stimuli). The whole process sort of sorts out the chaos – ie, it gives some meaning to the signal patterns that are perceived, converting them into useful information.

The set of biological processes involved in the acquisition, retention and use of information is called cognition. Among animals, cognition determines behavior patterns (eg, mode of foraging, choice of mates and escape from predators). Many of these patterns, of course, have obvious and direct implications for the lives of organisms. This is how “against a continuous background of odors in a prairie, an animal will respond to an unexpected odor, perhaps that of a predator.”[2]

The study of cognition is a complex, multidisciplinary field that is still in full swing. And it also has its shortcomings. Thus, although the use of information (understood here as decision-making) is something relatively well studied, other variables have been less explored. This is the case of studying the evolutionary implications of characteristics such as perception, learning, memory and attention.[3]

Under normal circumstances, sensory selectivity should generate appropriate responses. This is how “the energy of just one molecule of certain substances is enough to elicit nerve firings from a chemoreceptor”.[4]

Contrary to what some people imagine, the sense organs (eyes, ears, etc.) are not wide open windows – that is, we are not capable of perceiving everything that actually happens around us. Nor are sense organs perfect or even reliable filters. They are biased as they are selective. Our sensory experience, therefore, does not give us a picture of the world. What she gives us is, at best, only a hunch, an unfinished sketch.

The comment above can be converted into a warning: Any type of knowledge that is based solely on sensory impressions tends to lead the observer to errors and misunderstandings. Which is why the map of the world that we carry with us should be treated with distrust.


If the map of the world that we carry with us is not a faithful portrait, but a biased sketch, then the subjective notion that we develop about the things that surround us must itself be partial and incomplete. An unrestrained and unreflective adherence to our sensory impressions would therefore be naive and misguided, as well as potentially disastrous.[5]

*Felipe APL Costa is a biologist and writer. Author, among other books by What is darwinism.


Dangles, P & More 3. 2009. Variability in sensory ecology: expanding the bridge between physiology and evolutionary biology. Quarterly Review of Biology 84: 51-74.

Dennett, DC. 1997 [1996]. types of minds. RJ, Rock.

Dukas, R. 2004. Evolutionary biology of animal cognition. Annual Review of Ecology, Evolution and Systematics 35: 347-74.

Lent, R, ed. 2008. Neuroscience of mind and behavior. RJ, G Koogan.

Messenger, JB. 1980 [1979]. Nerves, brains and behavior. SP, EPU & Edusp.

Silveira, LCL 2008. The senses and perception. In: Lent (2008).


[1] Such organs act as transducers, converting certain types of external energy (chemical, sound, etc.) into internal electrical signals. Human beings, as noted by Silveira (2008, p. 181), “[Have] five special senses – sight, smell, taste, hearing and balance – in addition to a general sense, somesthesia. The latter has two very different facets. One of them is focused on the environment and the control of posture and movements. Another, homeostatic, is aimed at representing the subjective notion of the self and its physiological state, as well as the control of organic functions”.

[2] Quote taken from Messenger (1980, p. 13).

[3] In a nutshell: perception (= translation of signals from the outside into neuronal representation), learning (= acquisition of neuronal representation for new information), long and short term memory (= passive or active representation of already acquired information) and attention (= neuronal representation activated at a given moment) – for details, discussion and references, see Dukes (2004); in port., Lent (2008).

[4] Quote taken from Messenger (1980, p. 13).

[5] This critical notion is itself the fruit of modern experimental science. For comments and references on a classic study of "what the frog's eye tells the frog's brain," see Messenger (1980, p. 51-2); for an introduction to physiology and sensory ecology, see Lent (2008) and Dangles et al. (2009).

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