Discovery Lab Answers

The question names both Marilyn J. Schlitz, PhD and Richard Wiseman, and the evidence base is built around the collaborative experimenter-effect program they ran together. Before drawing any conclusions, a necessary qualification: the library’s share of the published literature on this question has not been measured, so what follows summarizes what the ESP-Nexus library currently holds, not a settled account of the full field. The chart below plots Cohen’s h effect sizes against publication year for the subset of results on that metric.

Marilyn J. Schlitz, PhD — The Wiseman–Schlitz Experimenter-Effect Program

Schlitz is a social anthropologist and consciousness researcher; her ESP-Nexus profile is at Marilyn J. Schlitz. The program examined here is among the most methodologically distinctive in modern parapsychology: a sustained, pre-agreed collaboration between a proponent (Schlitz) and a skeptic (Wiseman), running identical protocols side by side to isolate whether the experimenter — not the protocol — determines the outcome.

Experiments

Three joint remote-staring studies form the core of the program, all co-authored by both researchers.

Wiseman & Schlitz (1997) was the founding study. Each author independently ran a batch of participants through an electrodermal activity (EDA) staring-detection protocol. The two batches were run at separate sites — Wiseman’s at his UK laboratory, Schlitz’s at the Institute of Noetic Sciences — using equipment and procedures agreed in advance.

Wiseman & Schlitz (1999) was an attempted replication, explicitly designed to revisit the divergent 1997 results with tighter controls, including a crossover randomization scheme (ABBA/BAAB) to minimize progressive error.

Schlitz, Wiseman, Watt & Radin (2006) was the third and most elaborated joint study, adding a 2×2 crossed design in which the experimenter greeting the participant was varied independently of the experimenter acting as sender, and recruiting Dean Radin as a third experimenter. A mid-study sample-size reduction (from a larger planned N to 100 participants, 25 per cell) was made in April 2004 before any data were examined.

A published interview study, Watt, Wiseman & Schlitz (2002/2005), probed both researchers directly about procedural and psychological differences — particularly in pre-session preparation — to identify candidate mechanisms for their divergent results.

Separately from the joint program, Schlitz (1997) contributed to a broader meta-analytic synthesis of distant mental interaction with living systems (DMILS) experiments using EDA, covering 30 studies across multiple laboratories. A study of Juilliard musicians as receivers (Schlitz, 1992) and a distant-healing intention study (Schlitz, 2012) and a retroactive priming experiment (Schlitz, 2021) represent other research lines.

Methodology

The 1997 and 1999 studies shared a common EDA protocol: a “receiver” sat alone in a shielded room connected to skin-conductance sensors; a “sender” in a separate room alternated between staring at a closed-circuit camera feed of the receiver and looking away, in a computer-randomized sequence. The receiver had no sensory access to the sender’s state. The primary outcome was EDA amplitude during stare epochs versus non-stare epochs. The ABBA/BAAB randomization used in 1999 was introduced specifically to control for equipment warm-up and habituation effects.

The 2006 study extended the design to a full 2×2 crossover: Condition A (Schlitz as both greeter and sender), Condition D (Wiseman as both greeter and sender), and two crossed conditions. This allowed the greeting interaction — a pre-session contact that differed markedly between the two experimenters — to be tested as a separate factor. Participant assignment across conditions used pre-determined randomization, and the sample-size reduction was logged before data access.

A methodological specificity surfaces in the 2002/2005 interviews: the two experimenters differed substantially in what they did during non-stare periods. Wiseman reported doing nothing in particular; Schlitz described actively engaging with the session — sometimes reading, sometimes focusing mentally on the participant. This behavioral asymmetry became one of the principal candidate explanations for the outcome divergence, alongside participant belief levels (which trended higher in Schlitz’s groups but not significantly so in 1999) and subtle pre-session social cues from experimenter greeting style.

In the 1992 Juilliard study, receivers were musicians selected on the hypothesis that artistic sensitivity might correlate with psi receptivity — a non-standard sampling criterion that distinguished it from general-population DMILS work.

Data

The evidence base contains 13 result rows across seven studies. The metrics are not uniform — Cohen’s h, Cohen’s d, Pearson r, and p-only results are all present — and must not be averaged or pooled across metric types. The chart below covers the Cohen’s h results. The full picture, including nulls and direction, is:

†Note on direction coding: the structured evidence rows for 1997 and 1999 flag Schlitz’s conditions as “positive” (the pre-specified direction of greater EDA during stare epochs), though the Cohen’s h values themselves are negative — this reflects the signed metric convention in the database; the labeled direction is toward the predicted effect.

Several things stand out across this set, and the unsettled signals must be stated plainly:

• Eight of 13 result rows are null or below-chance in direction. The positive results are concentrated in Schlitz’s own conditions in 1997 and 1999, and in the older 1992 and 1997 meta-analytic work.
• The experimenter asymmetry is real in the data but not statistically confirmed as the cause. In both 1997 and 1999, Schlitz’s participants reached or approached significance while Wiseman’s did not, yet the direct comparison of detect scores between the two groups was non-significant in both studies (p =.17 in 1997; p =.44 in 1999). The difference between experimenters’ results was not itself statistically established.
• The 1999 effect ran in the opposite direction to 1997. In 1999, Schlitz’s significant result (ES = –0.33, p =.05) reflected lower EDA during stare epochs rather than higher — which is the reverse of the predicted direction. The evidence base flags this as a directional disagreement.
• The 2006 crossover study found no significant effect for either experimenter under any condition, and no main effect of greeter identity.
• Heterogeneity across the Juilliard, DMILS meta-analysis, distant-healing, and retroactive-priming studies is substantial; these are different phenomena, different protocols, and different outcome measures, and the results range from a large positive (ES = 0.52 in 1992) to flat nulls (p =.22 and p =.46 in 2021 and 2012).

Skeptical critiques

What critics argue. No published critique of this work appears in the sources retrieved for this question.

The 1999 paper itself notes that the 1999 effect — while nominally significant in Schlitz’s condition — ran in the wrong direction (lower EDA during stare), which complicates a straightforward psi interpretation. The authors acknowledge this directly. The paper also records that participant belief levels trended higher in Schlitz’s group but not significantly so, leaving open the question of whether belief-related participant behavior mediated the result.

What the experimental data show. The 2006 study was designed in part to test the greeting-interaction hypothesis — that Schlitz’s pre-session social contact with participants created a different psychological state — by crossing greeter and sender roles independently. Neither the Schlitz-only nor the Wiseman-only condition produced a significant effect, and the main effect of greeter identity was null (p =.50). If the greeting interaction were the primary driver of the earlier asymmetry, a significant greeter effect would have been expected; it was not found.

The 1997 meta-analysis, covering 30 DMILS studies across multiple independent laboratories, found a positive pooled effect (ES = 0.25, z = 6.17), which Schlitz has cited as evidence that the effect is not unique to her laboratory. However, this pooled figure spans a heterogeneous set of studies and laboratories, and the meta-analysis is a separate line of evidence from the experimenter-effect comparisons.

Analysis. The program is notable precisely because the same protocol, administered by two researchers with opposite prior beliefs, produced systematically different outcomes across two of three studies — but without a statistically confirmed difference between their participants’ detect scores. The 2006 study did not replicate the earlier asymmetry under either experimenter. Watt, Wiseman and Schlitz identified several procedural and psychological asymmetries (pre-session preparation, sender behavior during non-stare periods, participant belief levels) as candidate mechanisms, but none has been experimentally isolated as the cause. The direction reversal in 1999 adds a further complication that neither a psi nor a simple social-influence account resolves cleanly. Publication of all three studies was co-authored by both researchers, which is itself an unusual feature of the record — the disagreement is documented jointly rather than argued in separate papers.

For the broader research record, see Marilyn J. Schlitz on ESP-Nexus.