In the 1930s, Joseph Banks Rhine conducted experiments* with Zener cards in the laboratory at Duke University. Later, these studies became one of the grounds for Jung’s theory of synchronicity.
In the experiments, the deck consisted of 25 cards: five cards each with a circle, cross, wavy lines, square, and star.
The cards were shuffled and hidden from the participant. The participant’s task was to name the symbol on each card being revealed without seeing it. With five possible options, random guessing should have produced an average of five correct answers out of twenty-five.
At first, fairly broad groups of participants were tested. Later, the research continued with those who showed results above chance level.
And such people were indeed found.
Rhine’s Experiments: Distance and Precognition
But the experiments became especially interesting when the participant and the card being guessed were in different rooms. It turned out that for some participants the result remained above chance level even as the distance increased.
Then experiments with precognition appeared: the participant named the sequence of cards in advance, while the order of the deck was determined later. In some such series, the results also turned out to be above chance level.
The results of the experiments were interpreted as indicating that there are cases in which spatial distance seems not to matter. And temporal sequence does not either.
From Rhine’s Experiments to Jung’s Synchronicity
Carl Gustav Jung took the next step. He proposed that psychological and physical events can in some cases be connected acausally** — without a cause-and-effect transfer of influence from one event to another.
He developed this thought further: an inner state and an external event can coincide in meaning and be regarded as connected manifestations of one deeper reality.
For Jung, the assumption based on Rhine’s experiments became one of the steps toward creating the theory of synchronicity.
In analytical psychology, it found reflection in the approach to working with clients. More about this in other articles.
* A book describing the experiments in detail can be found freely available online: Extra-Sensory Perception, J. B. Rhine.
** Acausality in Jung is a connection between events that is not carried out through physical or energetic influence unfolding in space and time. The correspondence between the events is understood as a manifestation of a common meaningful or archetypal ordering.
If event A once caused psychological state B, which later caused event C in the external environment, this is a causal connection: A(t1) → B(t2) → C(t3).
In Jung’s synchronicity, a different relation is assumed: B ≈ C — the psychological and external events correspond to each other in meaning without a physical or energetic cause-and-effect transfer between them.