Natal astrology, also known as genethliac astrology or genethlialogy, is a system of astrology that claims to shed light on an individual’s personality or path in life based on constructing a horoscope or natal chart that includes the exact date, time, and location of an individual's birth. Natal astrology is found in the Indian, Chinese, Hellenistic and Western astrological traditions. A horoscope illustrates the positions of the Sun, Moon, planets, Ascendant, Midheaven, Descendant and Immum Coeli as well as the aspects or angles between them. Interpretation includes noting the placement and significance of important features. Chart Weighting analyzes Zodiac Signs and Houses. Chart Shaping analyzes planetary aspect patterns. In general, astrology is considered to be a pseudoscience by the scientific community. There is little statistical evidence that shows causation between horoscopes and the consequences in a person's life or those that may occur throughout the world.

Features

Within a horoscope, important features of significance may include the planets, aspects, Signs and Houses of the Sun, Moon and Ascendant. The Ascendant has a very strong influence. It is also known as the Rising Sign or Chart Ruler. This may also include one of the first three houses that follow an Ascendant. If no planet occupies the first three houses, a planet in the twelfth house, that is closest to the Ascendant, may be acknowledged as the Rising Sign. Planetary aspects that are in Conjunction or adjacent to the primary angles of the Ascendant, Midheaven, Descendant and Immum Coeli may also be important features.

Chart weighting

Chart weighting analyzes significant categories. This may include the Signs and Houses of the Sun, Moon, planets, Ascendant, and Midheaven. For example, if multiple planets are in Fire Signs, the attributes of those signs give more importance or 'weight' to a person's personality.

Weighting by sign

Chart weighting by sign analyzes masculine or feminine signs as well as elements and their qualities. Elements include fire, earth, air or water. Qualities include cardinal, fixed or mutable. Some astrologers may only use ten or eleven planets. Others may only include the Ascendant and Midheaven. The modern planets of Uranus, Neptune and Pluto may be excluded, because they influence generations; their positions may not have significance in a person's individual chart.

Chart Signature

A Chart Signature summarizes the process of weighting with a single Zodiac Sign. This involves noting which element and quality has the most signs and then combining them into a single Zodiac Sign, which is acknowledged as the Signature Sign of the chart. In a Natal Chart, a Signature Sign may have more influence than any other sign. For example, if a chart has more Fire Signs than any other element and more Fixed Signs than any other quality, then Leo is acknowledged as the Signature Sign of that chart, because it is a Fixed Fire Sign. If there are no majorities in element or quality, the sign of the ruling planets of the Sun or Ascendant may be added. For example, if the Sun is in Taurus, the sign of its ruling planet of Venus is added to its appropriate element and quality. If Venus is also in Pisces, the sign that occupies Pisces is also added in the same way.

Weighting by House

Chart shaping

Chart shaping involves examining the placement of the planets in the chart by the aspects they form and by their positioning in the chart relative to one another. Any significant patterns or 'shapes' which occur in the chart are then interpreted for their importance to the personality of the native.

Aspect patterns

While the astrologer must note every aspect formed by the planets, aspects can be grouped together into larger patterns which must be given particular attention in the chart. The main aspect patterns are as follows:

Hemispheres

The houses are grouped into four main categories or hemispheres. Horoscopes appear 'upside down' in relation to how the compass points usually appear, with the ascendant marking the eastern horizon traditionally appearing on the left hand side. For this reason the southern hemisphere appears in the upper part of the horoscope.

Jones patterns

The American astrologer Marc Edmund Jones has listed seven significant patterns which also occur in the chart, based on the positions of the planets relative to one another.

Scientific appraisal

Carlson's experiment

Shawn Carlson's double-blind chart matching tests, in which 28 astrologers agreed to match over 100 natal charts to psychological profiles generated by the California Psychological Inventory (CPI) test, is one of the most renowned tests of astrology. The experimental protocol used in Carlson's study was agreed to by a group of physicists and astrologers prior to the experiment. Astrologers, nominated by the National Council for Geocosmic Research, acted as the astrological advisors, and helped to ensure, and agreed, that the test was fair. They also chose 26 of the 28 astrologers for the tests, the other 2 being interested astrologers who volunteered afterwards. The astrologers came from Europe and the United States. The astrologers helped to draw up the central proposition of natal astrology to be tested. Published in Nature in 1985, the study found that predictions based on natal astrology were no better than chance, and that the testing "clearly refutes the astrological hypothesis".

Dean and Kelly

The scientist and former astrologer Geoffrey Dean and psychologist Ivan Kelly conducted a large scale scientific test, involving more than one hundred cognitive, behavioural, physical, and other variables, but found no support for astrology. Furthermore, a meta-analysis was conducted pooling 40 studies involving 700 astrologers and over 1,000 birth charts. Ten of the tests, which had a total of 300 participating, involved the astrologers picking the correct chart interpretation out of a number of others which were not the astrologically correct chart interpretation (usually 3 to 5 others). When the date and other obvious clues were removed, no significant results were found to suggest there was any preferred chart. A further test involved 45 confident astrologers, with an average of 10 years of experience, and 160 test subjects (out of an original sample size of 1198 test subjects) who strongly favoured certain characteristics in the Eysenck Personality Questionnaire to extremes. The astrologers performed much worse than merely basing decisions off the individuals' ages, and much worse than 45 control subjects who did not use birth charts at all.

Mars effect

In 1955, astrologer and psychologist Michel Gauquelin stated that although he had failed to find evidence to support such indicators as the zodiacal signs and planetary aspects in astrology, he had found positive correlations between the diurnal positions of some of the planets and success in professions (such as doctors, scientists, athletes, actors, writers, painters, etc.) which astrology traditionally associates with those planets. The best-known of Gauquelin's findings is based on the positions of Mars in the natal charts of successful athletes and became known as the "Mars effect". A study conducted by seven French scientists attempted to replicate the claim, but found no statistical evidence. They attributed the effect to selective bias on Gauquelin's part, accusing him of attempting to persuade them to add or delete names from their study. Geoffrey Dean has suggested that the apparent effect may have been caused by inaccurate self-reporting of birth dates by parents rather than any intentional manipulation of the study results by Gauquelin. The suggestion is that a small subset of the parents may have had changed birth times to be consistent with better astrological charts for a related profession. The sample group was taken from a time when belief in astrology was more common than today. Gauquelin failed to find the Mars effect in more recent populations, in which a nurse or doctor recorded the birth information. The number of births under astrologically undesirable conditions was also lower in the initial study, further indicating that parents had reported dates and times to suit their beliefs.