Where association ends. A review of associative learning in invertebrates, plants and protista, and a reflection on its limits.

Abstract

Since the beginning of the 21st century, the Minimal Cognition approach has emerged vigorously, focusing on the study of the adaptive behavior of the simplest organisms, including bacteria, assuming that they are sentient and information-processing entities. Although Minimal Cognition has occasionally used Pavlovian methods to try to demonstrate Associative Learning, neither the Psychology of Learning nor the Comparative Psychology traditions are prominent in the movement. However, the Psychology of Learning approach, with its highly sophisticated experimental designs, has done a great deal of research on Associative Learning in animals and carried out several studies on plants and unicellular organisms. The present work offers a comprehensive review of these experimental results, among invertebrates, plants and unicellular organisms (paramecia and the amoeba Physarum policephalum) showing that, while there are increasing instances of Associative Learning in many invertebrate phyla (and also many phyla with no data) there is no adequate evidence of it in unicellular protists (despite more than a century of experiments with paramecia and amoeba) or in plants (despite recent results that so claim). We then consider the alternative offered by Minimal Cognition and suggest some complementary ideas, from a Comparative Developmental Psychology approach, which we call “Minimal Development.”

Externalized memory in slime mould and the extended (non-neuronal) mind

“…It has been recently emphasized that the findings of some of the learning experiments that we rely upon in our paper are inconclusive because the experiments have yet to be repeated (seeLoy et al, 2021). Upon repeating these experiments, failure to replicate the same findings would of course count as evidence against ascribing certain forms of learning and memory to Physarum.…”

Principles for coding associative memories in a compact neural network

“…Ample studies demonstrated associative (conditioning) learning in C. elegans ( Ardiel and Rankin, 2010 ; Cho et al, 2016 ; Kauffman et al, 2010 ; Loy et al, 2021 ; Oda et al, 2011 ; Sasakura and Mori, 2013 ). In this study, we systematically mapped each of the four types of associative memories (short- and long-term memories, each encoded using positive and negative associations) onto the compact neural network of C. elegans .…”

“…Though equipped with a small neural network, C. elegans can form both associative and non-associative memories ( Ardiel and Rankin, 2010 ; Loy et al, 2021 ; Sasakura and Mori, 2013 ). To form associative memories, worms are typically conditioned with a chemical (e.g.…”

Some properties of habituation of siphon withdrawal in the slimy clam (Ruditapes decussatus)

“…However, in that classi cation there are certain taxonomical mistakes. Some subphyla are confused with phyla, and more than twenty phyla were missing (Loy et al 2021). The taxonomical issue is important because, even though there is a case of a speci c species of a phylum in which a learning phenomenon has been demonstrated, it is not appropriate to generalize such results to the complete phyla, given the variability of each phylum.…”