The world’s first scientific search for extraterrestrial intelligence (SETI) was also the beginning of a decades-long exercise in patience and tenacity.

Astronomers have yet to detect any evidence of alien intelligence in the Milky Way galaxy despite spending thousands of hours scanning the cosmos for radio signals carrying extraterrestrial tidings. Given the sheer number of star systems in the galaxy that we know host planets, many of which appear to be habitable, the silence is conspicuous. Astronomers have posed a number of theories about why we haven’t received an extraterrestrial message ranging from the obvious possibilities that we’re monitoring the wrong wavelengths or targeting the wrong stars, to more imaginative explanations such as the zoo hypothesis, which suggests aliens know we exist and are choosing not to talk to us. 

Arguably the most disturbing theory was put forth not by an astronomer, but by a psychologist named Jack Baird. He raised the possibility that the reason we haven’t heard from aliens yet is due to fundamental limits of the human mind. It may very well be the case that extraterrestrials are sending messages and we simply are incapable of perceiving them, much like we are incapable of hearing beyond a narrow range of frequencies. If true, this raises the important question of whether we can overcome the natural cognitive limits that prevent us from tapping into the cosmic discourse and if so, how we go about doing it.

It’s an atypical question for a discipline that is typically focused on the purely technical challenges of interstellar communication.

After completing a Ph.D. at Princeton in 1964, the mild-mannered 26-year old returned to his native Vermont where he spent the rest of his career studying the intricacies of the human mind at Dartmouth College. Baird’s specialty was psychophysics, a branch of psychology focused on the relationship between the brain and the external world. He was fascinated with how humans perceive everything from numbers on a screen to raw physical space, and wrote hundreds of papers detailing the effects of external stimuli on our mental processes.

Fascinating work to be sure, but seemingly remote from anything having to do with extraterrestrial intelligence.

NASA thought otherwise. In 1979, the agency tapped Baird to join a study group designed to determine whether it was feasible to detect radio signals from an extraterrestrial intelligence. Today, NASA is not formally involved with SETI, but at the time the agency was seriously considering the prospect of communicating with aliens elsewhere in the galaxy. It had begun assembling teams of scientists to research the technical and conceptual issues involved with a scientific SETI program such as identifying the best radio frequencies to monitor for signals and the most likely star systems to host intelligent life. But NASA realized there were also important human factors that SETI needed to address, which is how Baird and Tyler Blake, a psychologist at California State University, became the only scientists who weren’t physicists, astronomers, or engineers involved in the agency’s early SETI efforts.

The basic question the duo sought to answer was whether humans would recognize an extraterrestrial signal if we received one. Although today SETI relies on sophisticated computer programs and artificial intelligence to identify promising candidate signals in radio telescope data, in 1979 it wasn’t so obvious that computers would be up to the task of sifting through all this cosmic noise without some human assistance. The problem is that any radio message we receive on Earth will likely be very faint by the time it reaches us and may be very hard to distinguish from the background radio noise of the universe, since we can’t know in advance what form this message will take.

As part of their research for NASA, Blake and Baird recruited 18 volunteers and tasked them with identifying simulated intelligent signals against a background of cosmic noise. The subjects were exposed to dozens of displays then identified the ones they thought contained an intelligent signal and their confidence in their judgment. Baird and Blake made a few surprising discoveries from their experiments. First, some signals, such as straight lines, were generally harder to detect than wavy or pulsed signals. Second, for any given signal, the subjects frequently would divide into two distinct groups — one group that was very confident that they saw a signal and one that didn’t see the signal at all.

Baird and Blake published their paper in 1982 and recommended that future research compare the accuracy of human detectors versus computers. (Interestingly, they remarked that humans have an advantage over computers because they don’t need the types of signals they’re searching for to be specified beforehand, but this is now well within the capabilities of modern AI.) Although Baird never did a follow-up study on signal detection with NASA, his research revealed the deep connection between human cognition and the prospects of the search for extraterrestrial intelligence.

He realized that if we were ever going to detect an alien message, it was critical to identify—and if necessary—correct for the biases introduced into the search due to the nature of human psychology.

A few years after he completed the NASA study, Baird published The Inner Limits of Outer Space, which is the first and only book to grapple with the psychological aspects of SETI. It is a work that raises far more questions than it answers, which probably accounts for its relative obscurity. (A few years ago I wrote a book about designing messages for extraterrestrials that required a comprehensive survey of the literature, and I did not find Baird’s book cited anywhere, even once.)

Although it may not have attracted the attention of the wider SETI community, the issues it grapples with are could be fundamentally important to the future of the search.

The Inner Limits of Outer Space draws on Baird’s background in psychophysics to examine the ways that SETI is influenced by the way our brains receive and process sensory information. One of the book’s main insights is that “people project human qualities into space and attribute human motivation to aliens.” In some ways, this is a necessary prerequisite to the search— we must assume that aliens, like us, want to communicate with an intelligent species on another planet.

But it can also bias the types of signals we look for by assuming that aliens also think and perceive as we do.

Today, for example, SETI is mostly focused on looking for narrow-band signals in specific regions of the radio spectrum and many researchers assume they will likely have mathematical qualities such as a pulsed signal representing numbers. But Baird points out that this is a bias introduced into the search because it is largely driven by scientists and engineers who may be accustomed to thinking about communication problems in a specific way.

"If we think the alien mentality is comparable to ours, then it makes good sense to use standard techniques to make contact,” writes Baird. “A rich variety of intelligences is found in the human population, but only one type places heavy weight on scientific thinking. My point is only that the language of science is not outside the psychological constraints that determine all other modes of human expression.”

The form of the messages we are looking for is greatly biased by other human factors such as their timing. We expect extraterrestrial messages to be received on human timescales such as over the course of several minutes, hours, or days. But what if the alien civilization has lifespans that are substantially longer than ours and sends a message whose pattern is only decipherable by monitoring it over the course of years, decades, or millennia?

We might never realize we are receiving that message because we will not notice the pattern on that timescale.

It would be easy to read Inner Limits as a pessimist’s take on SETI, but that would be a mistake. Baird takes a clear-eyed view at the way human psychology influences our attempts to find messages in the cosmic noise and acknowledges the intractable challenges it creates. He offers a few solutions for overcoming our innate biases, which range from fanciful ideas about training dolphins for signal detection to pragmatic suggestions about humans collaborating with computers to identify potential messages.

But his fundamental message is that, regardless of whether we ever actually detect an alien signal, the pursuit of this goal is one of the best ways to understand what it means to be human because it pushes us to the extremes of our capabilities, and forces us to grapple with our limitations. And if the search is successful, first contact could extend the frontier of human capabilities in ways that may never have been possible on our own.

From Baird’s perspective, SETI is a total win-win regardless of the outcome.

“The complexity [of the search] should be cause for involvement, not despair,” Baird writes. “Although the psychological boundaries of human thought and expression may seem manifest, these could be illusory. The actual potential of the human mind may be realized only when external conditions demand more, in which case the full story of humanity will not be told until we cope with the altogether unique conditions of interacting with an alien being of the same or higher intellect.”

Baird never lived to see first contact nor did he expect to. He recognized that the challenges faced by SETI might take centuries, if not millennia, to overcome—if they could be overcome at all.

Baird’s legacy lives on in the next generation of alien hunters like Kevin Peter Hand, who were inspired by his work. Hand is a planetary scientist at NASA’s Jet Propulsion Laboratory, where he helps lead a team building the robots that may one day explore the subsurface oceans of Europa, which many astrobiologists think may have the conditions for life. Hand studied with Baird as an undergraduate at Dartmouth and would frequently discuss the possibility of extraterrestrial life with Baird over coffee after class.

“We would grab coffee and talk about SETI and the sensory perception problem of contact,” Hand says. “I ended up double majoring in psychology and physics in no small part because of Jack’s influence. He had a wonderfully curious mind and I think he enjoyed talking about these things with someone studying in the physics department.”

A copy of Inner Limits sits on a shelf in Hand’s office at NASA and although he isn’t in the business of looking for intelligent aliens, he says he still finds Baird’s book to be a source of inspiration and a reminder to be careful assuming too much about what alien life might be like. “Jack was trying to break out of the constraints of our own psychological and sensory perception limitations,” says Hand.

“You’ve got to be a bit fearless when it comes to the search for life in the universe, especially intelligent life because it’s not really a field that is taken tremendously seriously academically. But it’s a profoundly important endeavor and he encouraged me to stay fearless and continue to pursue this stuff.”

When Baird wrote Inner Limits, NASA’s Viking lander had only recently landed on Mars carrying the first astrobiology experiment in history, and just a handful of small radio searches for intelligent extraterrestrial signals had been conducted. There was no guarantee that the hunt for life beyond Earth would ever garner the serious support it needed to be successful. But today, there is a multi-billion-dollar car-sized rover on Mars dedicated to looking for signs of ancient life, Hand is helping lead a scheduled mission to Europa that may be the first to detect biosignatures, and there’s now a global SETI program backed by $100 million that employs many of the world’s leading astronomers.

Far from giving up on the possibility of making contact with extraterrestrial life, the search is enjoying more support than ever before.

Still, there is no guarantee the search for life beyond Earth—intelligent or otherwise—will bear fruit. But as Baird realized, even if we turn up empty-handed, that doesn’t mean the effort wasn’t worth it. “The search itself fulfills a dual purpose,” Baird wrote in Inner Limits. “The manifest intent is to enlarge the perspective of humanity beyond the physical boundaries of Earth. The more subtle agenda is to use the cosmic search as a tool to examine the social and psychological factors behind the widespread interest in and curiosity about alien presence in the universe.

While each of us comes to grips with the implications of contact, it is hoped that we will also be learning more about ourselves.”