Alfred Binet

Binet argued that denying psychology to lower organisms forces one to assume it is added during evolution as organisms grow more complex¹. Binet held this to be inconsistent with general physiology, which finds vital phenomena already present in undifferentiated cells². The target was Romanes, whose chart assigned intellectual powers to successive zoological stages. Binet called that chart arbitrary³. In Romanes's scheme, as Binet reports it, lowest organisms have only protoplasmic movement and excitability, and memory begins with the echinoderms³.

The book's contents list shows the questions Binet took up. One was whether a single cell lacks a central nervous system and might have a diffused one, with Gruber's observation of the dividing Stentor as evidence. Another was whether ocular spots in flagellates and plant zoospores act as eyes. Binet gathered work by Klebs, Pouchet, Engelmann and others, including Engelmann's tests of light sensitivity in Euglena⁴.

Jennings named Binet's essay as a readable early treatment, presented frankly from the psychical standpoint, and credited Verworn with laying the foundations in 1889⁵. Jennings also quoted Maupas on hunting ciliates through Binet's book⁶. James cited Binet on dissociation in apparently anaesthetic patients⁷. James also disputed Binet's theory of hallucination, saying it explained many cases but not all, and citing Tuke's counterexamples⁸.