An honest comparison
Biorhythm vs astrology
Both start from your birth, both offer a personal reading of the day, and neither held up when it was tested. They differ in what they count: biorhythm counts only the days since you were born, and astrology reads the positions of the sun, moon and planets.
- Biorhythm counts
- the days since birth
- Astrology reads
- the sky at birth
Alike
What they share
- 01Both start from the moment of birth.
- 02Both turn that starting point into a reading for any day you ask about.
- 03In the 1970s, newspapers printed biorhythm charts as well as horoscopes.
- 04Both were tested by scientists, and neither predicted what it claimed to.
- 05Both are used today for much the same reason: as a prompt to think about the day.
Apart
Where they differ
| Biorhythm | Astrology | |
|---|---|---|
| Starts from | Your date of birth | Your date, time and place of birth, for a full chart |
| Counts | Days since birth, divided by 23, 28 and 33 | The positions of the sun, moon and planets against the zodiac |
| Worked out by | Arithmetic anyone can do by hand | Tables of planetary positions, then an astrologer's reading |
| Same result for | Everyone born on the same day | Everyone born at the same time and place |
| Age | Proposed between the 1890s and the 1920s | Thousands of years old; its zodiac comes from ancient Babylon |
| Claims | Three cycles in body, feeling and thought | An influence of the sky on character and events |
The record
How each was tested
134
studies of biorhythms, reviewed in 1998
Biorhythms were checked against accidents, sport, exam marks and deaths through the 1970s and 1980s. In 1998 Terence Hines reviewed 134 of those studies and concluded that the theory is not valid. Are biorhythms real? has the detail.
1985
a double-blind test of astrology, in Nature
Astrology has been tested many times too. The best-known test is a double-blind study the physicist Shawn Carlson published in Nature in 1985: astrologers were given people's birth charts and asked to pick, from three personality profiles, the one that belonged to each person. They did no better than guessing would.
Human nature
Why both can feel right
4.26out of 5
In 1949 the psychologist Bertram Forer gave each of his students a personality description, written, he said, for them alone. Every student received the same text, assembled largely from a book of horoscopes, and on average they rated it 4.26 out of 5 for how well it described them. A reading written in general terms fits almost anyone; the days it fits are remembered and the days it misses are forgotten. Horoscopes and biorhythm readings both benefit from that, as any personal reading does.
BioCalendar
How BioCalendar uses it
We treat a biorhythm the way many people treat their horoscope: as something to reflect on, not something to obey. BioCalendar counts the three cycles from your date of birth and shows the reading for the day. It does not chart the planets, and it never claims that a reading is accurate or predicts anything. The editorial policy sets out how we write.
Sources
- Carlson, S. (1985). A double-blind test of astrology. Nature, 318, 419–425.
- Forer, B. R. (1949). The fallacy of personal validation: a classroom demonstration of gullibility. Journal of Abnormal and Social Psychology, 44, 118–123.
- Hines, T. M. (1998). Comprehensive review of biorhythm theory. Psychological Reports, 83, 19–64.
Continue the story
Keep going
- 01What is a biorhythm?A biorhythm is a cycle said to begin at birth and repeat on a fixed period: 23 days physical, 28 emotional, 33 intellectual. The theory and the evidence.
- 02Are biorhythms real?What the studies found when they tested biorhythm theory against accidents, sport, exams and deaths, why people use it anyway, and how we frame it.
- 03Biorhythm vs circadian rhythmA circadian rhythm is a measured body clock of about 24 hours, reset by daylight each morning. A biorhythm is a cycle counted from birth. How they differ.