What Can Spiders Hear?

It is astounding to read that scientists are able to implant electrodes in the brains of spiders to show that their neurons respond to sound. But to read on the same page that Gil Menda thinks spiders also can respond to different tones in his voice is even more interesting (New Scientist, 22 October, 2016, p16).

It has been assumed that spiders ‘hear’ because they have hairs sensitive to vibrations. Menda’s research with the jumping spider Phidippus audax showed that their auditory sensitivity extended to more than 3 metres – more than 350 body lengths. The response of spiders to ‘tones’ of voice is so far anecdotal. Menda’s conviction is based on the informal naturalism some of us indulge – eg. talking to spiders around one’s home, or anywhere else. The implications of our efforts to attempt to communicate more sensitively with spiders (and other insects) are considerable.

To begin with insects, like all life-forms, are obviously aware of ‘others’ in their environments; survival depends on this ability. ‘Hearing’ vibrations is also unsurprising – the human ear also works with vibration sensitive hairs. But hearing different tones raises the possibility that spiders, and other insects, can somehow distinguish between different human emotions. In human communication ‘tone’ is decoded from physical signs like auditory volume and pitch, and the visual cues of ‘body language’. Perhaps spiders are able to decode physical signals too.

In other words our ability to read other human’s emotional states may not be much more sophisticated than spider behaviour. Indeed when one considers that some species are able to detect tiny changes in chemical concentrations or electrical charge the possibility that other species may be able to read our emotions better than other humans arises.

Of course humans pride themselves on being ‘empathetic’, in the sense of being able to imagine what the ‘other‘ is experiencing. Our communication with other humans, and our sense of self, is a partial product of this (very largely) learned ability. But it remains true that we can never be quite sure what the ‘other’ is experiencing, or thinking. Our confidence with human ‘others’ largely arises from our language skills and assumptions of similarity that appear to ‘work’. But we can be isolated in a world of individual experience – as people with Asperger Syndrome appear to demonstrate.

There are further implications. If we credit all life-forms with the ability to be aware and ‘feel’, ‘self-awareness’ also seems most likely. The additional ‘step’ of admitting the communication of emotions across different species, also raises the possibility that the ‘intelligence’ of other life-forms is much more like human intelligence than previously assumed.

Whether or not we do come to make adequate allowances for the cultural differences between species (and all life), it should be clear that we do actually have enough evidence (scientific and anecdotal) to relativise conventional ecological scenarios. Humans are only one life form among many and are not that different to other life forms that we routinely ignore and destroy. It may seem remarkable that this point needs to be made, but it does. The granting of rights to other species, ecologies and habitats depends on the ability of humans with the power to make legal arguments, enact new laws, and police existing laws protecting non-human life to become more convinced of the need for a relativised ecology. All environmental defenders and environmental legislators will also encounter some very obtuse politicians among those more enlightened. Allowing insects and other species the possibility of being emotional is a small step in the direction of overcoming deeply embedded human prejudice.