Wilhelm Wundt

Wilhelm Wundt appears in the book as a psychological authority on how sensory impressions become dream illusions. His account links the uncertain signals received in sleep to the psyche’s use of memory, while his discussion of internally generated visual and auditory phenomena offers another possible source of dream imagery.

Sensory Impressions and Illusion

Wundt’s explanation of dream illusion closely resembles Strümpell’s. A sleeping psyche receives sensory impressions under conditions that make accurate recognition difficult; when an impression is not sufficiently strong, clear, and enduring, or there is too little time to reflect on it, the mind may mistake it for something else. The book illustrates this principle with an indistinct object seen at a distance: it may first seem to be a horse, then a cow, before closer observation reveals a group of people. Sleep impressions are similarly indefinite, and the images they evoke give the impressions their psychological value.

In this account, an external stimulus does not dictate a dream-image by itself. It prompts remembered images, and these associations help determine how the impression is experienced. The selection among memory-spheres and associative connections remains difficult to specify in the theory Wundt shares with Strümpell. The book consequently leaves open whether the sensory stimulus alone can explain a dream’s detailed content, or whether other factors guide which memories are brought into play.

Subjective Sensory Excitations

Wundt also proposes that internally generated sensory phenomena can help produce dream illusions. He points to visual and auditory experiences familiar even in waking life, including dazzling light against a dark visual field and ringing or buzzing in the ears. He gives particular importance to subjective retinal excitation as a possible explanation for dreams filled with many similar or identical objects.

On this hypothesis, scattered points of light in a dark field can be elaborated into numerous images: birds, butterflies, fishes, coloured beads, or flowers. Their apparent movement follows from the mobility of the shimmering light, while the variety of animal forms reflects the dream’s capacity to adapt its inventions to the shape of these subjective visual phenomena. Wundt’s account thus treats dream imagery as an interpretation of sensory material, whether that material comes from outside the sleeper or arises within the sensory organs.

Evidence and Limits

Subjective excitations have a practical advantage as a proposed source: unlike external stimuli, they are not dependent on chance and are available whenever an explanation calls for them. But the book gives them a weaker evidentiary standing. Their role is difficult or impossible to establish through observation and experiment in the way that the dream-arousing effect of objective stimuli can be tested.

The principal support offered for their influence is the phenomenon of hypnagogic hallucinations, vivid and fluctuating images that often arise as people fall asleep and may persist briefly after the eyes open. The book presents this evidence while maintaining the distinction between a plausible explanatory source and one whose operation can be experimentally confirmed. Wundt’s indexed contributions include sensory stimuli and psychical activity in dreams, placing his account within a broader discussion of how perception and memory participate in dream formation.