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# Habituation in non-neural organisms: evidence from slime moulds

## Details

**Authors** Boisseau et al

**Year** 2016

**Publisher** Royal Society Publications

**Discipline** Biology

[Read it at the publisher](https://doi.org/10.1098/rspb.2016.0446) 
10.1098/rspb.2016.0446

## In authors' words

### Abstract

Learning, defined as a change in behaviour evoked by experience, has hitherto been investigated almost exclusively in multicellular neural organisms. Evidence for learning in non-neural multicellular organisms is scant, and only a few unequivocal reports of learning have been described in single-celled organisms. Here we demonstrate habituation, an unmistakable form of learning, in the non-neural organism Physarum polycephalum . In our experiment, using chemotaxis as the behavioural output and quinine or caffeine as the stimulus, we showed that P. polycephalum learnt to ignore quinine or caffeine when the stimuli were repeated, but responded again when the stimulus was withheld for a certain time. Our results meet the principle criteria that have been used to demonstrate habituation: responsiveness decline and spontaneous recovery. To distinguish habituation from sensory adaptation or motor fatigue, we also show stimulus specificity. Our results point to the diversity of organisms lacking neurons, which likely display a hitherto unrecognized capacity for learning, and suggest that slime moulds may be an ideal model system in which to investigate fundamental mechanisms underlying learning processes. Besides, documenting learning in non-neural organisms such as slime moulds is centrally important to a comprehensive, phylogenetic understanding of when and where in the tree of life the earliest manifestations of learning evolved.

### What they set out to do (purpose)

To investigate learning in non-neural organisms

### What they found (results)

The more times they exposed the slime mold to the stimulus, its response rate was less and less. Eventually, the mold learned to ignore the stimulus altogether. When given a break from the stimulus and then reintroduced, the process started over again.

## Commentary

### In short

The point of this and many other similar researches into unicellular and multicellular organisms, plants, etc, is that even non-neural organisms can learn and are building little mental models of their surroundings (however rudimentary) based on distinctions, systems, relationships, and perspectives.

### In more detail

Boisseau et al. 2016 investigated learning in non-neural organisms (i.e., a slime mold). A slime mold may not jump to mind as the ideal subject for research on the fundamental mechanisms of learning, however, Boisseau et al. states that maybe it should be. They define learning as “a change in behaviour evoked by experience.” In their research with the slime mold (Physarum polycephalum), they found that it developed habituation behaviour, an “unmistakable form of learning.” In their experiment, they exposed the mold to a stimulus (quinine or caffeine) and waited to see a response behavior (in this case, it was chemotaxis or movement based on a concentration of a substance). What they observed was remarkable. The more times they exposed the slime mold to the stimulus, its response rate was less and less. Eventually, the mold learned to ignore the stimulus altogether. When given a break from the stimulus and then reintroduced, the process started over again. These results open up a whole new world to the study of learning, as non-neural organisms have not typically been the focus for cognitive investigations which tend to focus on organisms with neurons and brains. What does it mean if learning can occur without neurons or brains? There are many implications. Of importance, this discovery shifts when the scientific community thought learning evolved, bringing the time much earlier than previously assumed. Second, this means that learning as a process is so fundamental to life itself that neurons, while helpful, aren’t necessary to make distinctions (i.e., stimulus from non stimulus) and to make something as complex as a perspectival shift (i.e., "stimulus is bad and warrants a reaction" to "stimulus is neutral and can be ignored"). The point of this and many other similar researches into unicellular and multicellular organisms, plants, etc, is that even non-neural organisms can learn and are building little mental models of their surroundings (however rudimentary) based on distinctions, systems, relationships, and perspectives.

**Patterns it shows** D, S, R, P

**How to cite this** Boisseau et al (2016). Habituation in non-neural organisms: evidence from slime moulds. Royal Society Publications.