Ignored in sight, out of mind: Human perception of plants

Although common and important parts of our lives, plants often go unnoticed and unappreciated. Overlooking plants begins within our minds with the ways that we recognize and classify objects and is reinforced when we neglect to gain the knowledge to more accurately describe and understand plants.
Ignored in sight, out of mind: Human perception of plants
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Introduction

In recent years, there has been growing recognition of an ignorance or under-appreciation of plants and there is even a term, plant awareness disparity (formerly plant blindness), a phenomenon wherein people deem plants as uninteresting scenery or sustenance (Balding & Williams, 2016; Parsley et al., 2022; Thomas et al., 2022). This under-appreciation operates at many different levels, it happens every day when our brains recognize and process visual signals of plants and decide whether or not to pay attention to them, and then later on whether to remember them. Importantly, this under-appreciation happens when we teach others about the world around us, including what to recognize and what is important. To better understand plant awareness disparity, I will discuss an important framework for object recognition (animacy) then where it ranks plants and why. Finally, I will discuss how this ranking and recognition is based on our own values and teachings, and what we should look for to further fill-in our knowledge on the lives of plants.

Animacy 

One way that our minds classify the many objects that we see every day is via animacy, which is a binary character (animate versus inanimate) indicating whether an object is alive and capable of intentional, goal-oriented movement (Vihman et al., 2018; Contini et al., 2021). For example, dogs and humans are clearly animate, whereas rocks and spoons are clearly inanimate.  Animacy in not only an interesting framework, but it can also affect how we think and what we prioritize. The ‘animacy effect’ is a possible processing advantage of animate over inanimate objects in which greater interest and memory retention is given to animate objects (VanArsdall et al., 2015; Gelin et al., 2017; Félix et al., 2019; Mieth et al., 2019; Sá-Leite et al., 2023) using pathways within our brain that are connected to memory (Henderson et al., 2021; Jozwik et al., 2022). There may be some limitations (Gelin et al., 2019; Daley et al., 2020; Blunt & VanArsdall, 2021) and the exact mechanisms are still unclear and may be strongly linked to item specific memory strength (Serra, 2021), yet the importance of some scale that aligns with animacy is largely accepted.

Animacy is organized at three levels: biology, cognition, and linguistics (Trompenaars et al., 2021). These describe how it is, how we see it, and how we say it.  All levels should be in agreement, yet our recognition of animacy is limited by our own perception, knowledge, and cultural biases. There are many objects that are more difficult to readily classify than dogs and rocks, and many objects may be perceived as animate although they are not alive, or inanimate although they are capable of movement (Félix et al., 2020; Westfall, 2022).  To be recognized as animate, an object must not just have motivated movement, we must also be able to perceive and recognize this movement. The information that we see and use to discern these categories can be split into both dynamic and featural attributes (Opfer & Gelman, 2011). Dynamic attributes are those that are moving and are thus the clearest and most direct signs of animacy. Very often, these attributes are absent, for example if looking at a picture of something or if an animal is sleeping, then we can use the featural attributes. Featural attributes are static and can be used to intuit that an object can move (such as the presence of articulated legs) or that it is an object already recognized as capable of moving (such as the ears and shape of a sleeping cat). Witnessing and recognizing movement involves dynamic attributes; featural attributes are thus more vital generally for category recognition.

Plants

Plants are biologically alive yet generally linguistically inanimate (as a rule enforced by grammar; Radanović & Milin, 2011; Bayanati & Toivonen, 2019). There are some languages where plants and sometimes even clearly inanimate and non-living objects are recognized as animate (Palmer et al., 2012; Kimmerer, 2017; Gillon, 2019; Holmberg, 2022) although this may align to human use and not the biology of the object (Dahlstrom, 1995). In studies on human perception and cognition, plants are placed in an intermediate region away from objects that are clearly animate or inanimate. Objects within this region include many non-living mobile objects such as constructs (e.g. cars) and natural phenomena (e.g. wind; Trompenaars et al., 2021; Sá-Leite et al. 2023). There are also many objects that are alive but lack clear dynamic attributes, including microorganisms, many animals, and especially plants. Additionally, plants are regularly the lowest ranked organisms on the animacy spectrum and even rank lower than non-living viruses (Trompenaars et al., 2021). The general consensus from linguistic and cognitive studies is that plants are, if not inanimate, not fully or clearly animate. Importantly, plants are the only visible and abundant living thing within the intermediate region.

An animate plant, hidden within soil.

Movement

Plants are clearly understood as alive (based on all definitions and recognized as such by children by an early age; Leddon et al., 2009), thus the lack of recognition of animacy is because of the way that plants live their lives, particularly their movement, and not if they are alive. Biological movement in general varies in type and perceptibility. Many non-living things have movement far more easily recognized than that of plants, such as cars or running water. In fact, plants may be seen moving because of the movement of wind or water, but this is rarely interpreted as plant movement (Marder, 2012; Segundo-Ortin & Calvo, 2023; Trewavas, 2009) and plants generally rank similar or slightly higher in animacy rankings than the natural phenomena (i.e. wind and water; Radanović et al., 2016; Trompenaars et al., 2021).  

Plants move in a variety of ways, some noteworthy dynamic examples are touch-triggered leaf movements by the Venus fly trap (Dionaea muscipula; Westfall, 2022) and the sensitive plant (Mimosa pudica; Volkov et al., 2010) or ballistic seed dispersal that launches seeds through the air (Hayashi et al., 2009). The vast majority of movement occurs at speeds too slow for us to recognize. Plants primarily move through growth (Lee & Calvo, 2022) with the formation and extension of stems, roots, and leaves, thus the ways that they move and live their lives are captured by their bodies (Arber, 1950; Bartušková et al., 2022). Aboveground, plant stems and leaves can sense and move towards light or the soil (i.e. phototropism and gravitropism), and also display complex helical movement (circumnutation; Darwin, 1888).  Belowground, plant organs can also grow in relation to soil depth and resources (Raunkiar, 1934). Plant roots can even contract and pull the whole body of the plant downward to maintain optimal depth in the soil for the plants to grow safely (Pütz, 1994; 1996; Pütz & Sukkau, 1996; Klimešová, 2018). This form of movement is all around us, especially in fields and meadows (Herben et al., 2018), but it occurs underground and goes unnoticed.

Intentionality

Intentionality is the most complex and controversial component for recognizing or delimiting animacy. Intentional movement should be goal-oriented and part of an interaction with the external environment (Sha et al., 2015; Vihman et al., 2018), yet the level of involvement and interaction to qualify as intentional is still disputed. Inclusive definitions claim that any system that can receive signals from and interact with the environment have intentionality, this would include even single cells (Morgan & Piccinini, 2018; Lee & Calvo, 2022). Most more limited and more exclusive definitions interpret that intentionality is only present when organisms are also capable of thought and consciousness similar to human capabilities (Searle, 1979). An emphasis on intentionality for recognition as animate has also caused some researchers to speculate that the animacy scale is actually a humanness scale, ranking the similarity to humans, and some models confirm that it matches better than pure animacy (Bayanati & Toivonen, 2019; Contini et al., 2020; Ritchie et al., 2021). Plants are clearly very different from humans; thus this may explain some difficulties in recognizing even featural attributes as conveying animacy.

For the perception and recognition of the intentionality of plants, there are the same problems as for more general movement: any intentionality that plants have would also go unrecognized because of an absence of dynamic attributes. Just as we recognize animacy when we see the jointed legs of animals, we can see from the twisting of stems and the scars of old leaves and stems that plants have grown and moved. We can dig up a potato or an iris rhizome and see how it is thickened and full of carbohydrates in preparation for growth the next year. Plants respond to external stimuli, and they can also exhibit complex behaviour as they purposefully and intentionally allocate and prepare for future events including predictable parts of annual seasonal cycles but also allocating additional resources in case of damage or other unforeseen threats (Calvo & Friston, 2017; Bartušková et al., 2022; Segundo-Ortin & Calvo, 2023)

Classification and knowledge 

The processes by which humans recognize and classify objects are shaped by our evolution and align with utility. Humans evolved to recognize plants to avoid toxic plants and identify edible or useful plants (Caramazza & Shelton, 1998; Moore & Price, 1999; Prokop & Fančovičová, 2014). This continued with herbaria for food and medicine, and this human-centred view is best exemplified by the doctrine of signatures which classified all plants and plant structures based on their similarity to the human body with the specious understanding that such structures would cure or heal the aligned human part (Bennett, 2007). Most notable of course is the mandrake with a root shaped like a human body, although it does not cure all ailments. Human knowledge and culture have generally developed beyond such ideas, but the bias toward human-like objects and utility for humans can still influence what we prioritize in our studies and education.

For objects in the intermediate region between recognition as animate or inanimate, the question is if they are being recognized as inanimate or failing to be recognized as animate (Westfall, 2022).  Without dynamic attributes to aid in the perception and recognition of animacy, we must apply our knowledge of the lives of plants and the visible representations of their movement (Lubbe & Castillo Alfonzo, 2024). The signs of plant movement and intention are present, the lack is in education and appreciation of these signs. For plants, there is clearly a failure to recognize the many aspects of their lives, present as featural attributes, that convey animacy. The rare situation when plants may be perceived with greater animacy or agency, are weeds (Benvenuti, 2004; van der Veen, 2014).  Weeds are any plants growing in a location where we do not want them (Benvenuti, 2004) and it is when plants trespass and go against their presence as scenery or utility that we recognize their activity.  When we neglect knowledge about plant bodies and lives, not only do we contribute to a general lack of understanding of the world around us, but more practically, we also ignore information that can help us to maintain the land and plant communities around us – including to avoid weeds.

An animate plant, gaining knowledge for plant appreciation.

Conclusion

Plants are very different from humans, yet they are also all around us and are fundamental parts of our every day lives. This is all the more reason to learn about them and appreciate them, especially because they are vital parts of our ecosystems. Plants grow and move and carry out complex interactions with one another and their environment. 

Our minds give importance to objects and organisms that are more similar to us and that move in ways that we can see and readily understand. Plants are different, yet they are important in our lives. Overlooking plants means overlooking their role in vital ecosystems and in fact those vital ecosystems themselves. We need to value plants because they bring value to us. Also, by ignoring the complex lives of plants, we miss out on knowing about the vividness of the world around us. It takes learning to recognize the signs of plant life history and movement, but I believe it is worth it.

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