Do Black Cats Cause Bad Luck?

What is superstition? According to The Little Oxford Dictionary, superstition is "belief in the existence or power of the supernatural; irrational fear of the unknown; a religion or practice based on such tendencies; widely held but wrong idea." Let us examine that definition in depth. First, there is "belief in the existence or power of the supernatural". This means that there is believed to be some force that can influence the events on the Earth. Second, there is "irrational fear of the unknown." This has been endemic to the human race since the early days when a cave man did not know if that cave was safe to enter or if he would be attacked by a bear. Third, "a religion or practice based on such tendencies." This is the belief that a charm or talisman, such as throwing salt or hanging a horseshoe over the doorway, can affect the aforementioned supernatural force. Finally, there is a "widely held but wrong idea." This is a belief that is believed only because everyone else believes. It maybe wrong, it may be preposterous, but all the other people think it is right and you believe it too.

Why do people believe in something that can be scientifically proven wrong? They may want a simple explanation for a coincidence. For example, a woman plants a tree in her yard and the weather is warm for the rest of the month. She reasons that planting trees causes warm weather. That is a simple, obvious conclusion. A weatherman will give a long, confusing explanation such as "Various meteorological factors caused displacement of the cold front." The woman will believe her own explanation because it is simple and easily understood. Once one person believes this conclusion, others will believe too. Perhaps the woman will be gossiping with some friends, and she mentions her tree superstition. They tell others and soon the whole town believes that trees cause warm weather.

Some examples of common, everyday superstition include the belief that the number 13 is unlucky, that walking under a ladder will bring bad luck, and that a black cat crossing your path can affect your luck. Belief that black cats affect your luck goes far back in time. One king of England, Charles I, owned a black cat. His fear of losing it was so great that he had it guarded. The day after it fell ill and died, he was arrested (Radford 1949, 40). Black cats were often witches in disguise or witches' familiars (Potter 1983, 29). There were also many cat charms relating to ships and the sea. Fishermen's wives would keep a black cat at home to prevent disaster at sea, consequently the cats became very valuable and were often stolen. If a cat ran ahead of a sailor to the pier that would bring good luck, but if the cat crossed his path it means bad luck. For luck, cats were often kept on board ships. If a sailor was approached by the ship's cat it meant good luck, but if the cat only came halfway and went away again it meant bad luck. The worst possible cat-related act, guaranteed to raise a storm and bring bad luck of all sorts, was to throw the cat overboard (Radford 1949, 40). Cat superstitions were also common in medicine. Fur and blood drawn from various parts of the cat's anatomy cured everything from shingles to St. Anthony's Fire (Radford 1949, 40).

All of these superstitions today boil down to "Black cats cause bad luck." A cat crossing your path will adversely affect your luck. This can easily be verified or disproved with only a person, a cat, and a situation that can be affected by luck.

I performed an experiment to test a black cat's effect on luck. Two people tried their luck at guessing computer-generated random numbers. Their paths were then crossed by a cat and then they guessed more numbers. To ensure that the luck effects were only caused by black cats, their paths were also crossed by a white cat.

The source of random numbers was a random number generator that I wrote in True Basic 2.6, a BASIC programming language for Macintosh computers. The random number, between 0 and 1, is calculated by factors including the date and time. The program's main loop appears below.

The first line of the program states that the program runs 50 times, to simulate 50 coin tosses. The computer requests that the user enter "h" or "t", as in "tails" or "heads" in a coin toss. Then a random number between 0 and 1 is picked. If the number is greater than one half (.5) then it counts as tails. If the number is less than one half it counts as tails. The computer compares the user's guess to its random choice. If the user was right then the computer adds 1 to its tally of correct scores. After 50 coin tosses the computer prints out the final percentage correct. Each person was tested five times and the results averaged, to minimize statistical errors.

The situation of the actual path-cross was a hallway with two doorways on opposite sides. As the subject walked down the hallway the cat ran out of one doorway and into the other.

The above diagram is a floor plan of the area in which the test subject encountered a cat. The human began on the left. As he walked down the hall, the cat was released in alcove A. The cat walked or ran across the human's path. The cat then proceeded into alcove B across the hall. The human continued to the computer room C. The subject then ran the luck program. The program was run five times immediately. The results were entered into a series of charts. Luck For Subject Alone is a chart of the subject's luck when his path was not crossed by any cats. Luck for White Cat is a chart of when the subject's path was crossed by a white cat. Luck for Black Cat is a graph of the subject's luck when his path was crossed by a black cat.

The lower line in each chart is the lowest percentage that a subject received. The upper line is the highest percentage that the subject received. The center line is the actual percentage of coin flips correct.

The first subject, according to "Luck for Subject Alone", scored between 56% and 44% for all his tries. The percentages are near the upper range for all tries but the last. 1 out of 5 tries is at the lower range. The average of his tries was 52%: slightly above the statistical prediction of 50%. When his path was crossed by a white cat, his luck first decreased to 36%. This is a great drop taken by itself, but all the other 4 were near or at the top. The average percentage for a white cat was 49.2%, 2.8% below the subject's average and .8% below the statistical prediction. However, 3 out of 5 tries are not outside the original range. They are within the subject's average percentage range, but they are only slight drops from the statistical average of 50%. The subject's luck was decreased according to a random factor, not according to the cat's path-crossing.

These are the cats used in the experiment.

These results appear to agree with the superstition, even for the wrong cat color. I ran the test a second time to see if the white cat's results could be repeated. This time the results (see "Luck for second white cat crossing") were different. The subject's luck started out high, at 56%. Then it peaked at 58%. It then dropped to the lowest point, 40%, and went up through 48% and 50%. These percentages are higher than the drop observed earlier. The drop to 36% can now be seen as a random error, not related in any way to the white cat. If the cat truly was capable of decreasing luck, the subject's luck would have repeated the decline.

The black cat, surprisingly, caused less of a drop than the white cat. The black cat lowered the minimum percentage to 40%. The luck average was 47.2%. This range is still within the percentage range of the unaffected luck. The luck has not descended out of the average range of the subject.

The luck of the second subject was slightly different. His percentages were 40-52%, averaging 46.8%. When his path was crossed by a white cat, his success rate became 40-60%, averaging 49.6%. The white cat caused a gain in luck! The black cat caused an expansion in luck, to 36-56%. Both results go directly against the old superstition. If black cats are unlucky, then why did the subject's luck increase? One possibility is the corollary superstition that a black cat running away from you is bad luck whereas a black cat approaching you is good. But neither applies here. The cats crossed the subject's path at nearly a right angle. The cat did not move towards the subject or away from him. Secondly, the subject's luck range did not simple shift upward, it expanded. The minimum was lowered and the maximum was raised. The possibility for bad luck was there, but so was the possibility for good luck. This remains unexplained by the superstition.

In conclusion, neither cat produced a drastic change in the subject's luck. True, the subject's luck declined slightly, but the change was not great enough to leave the subject's average luck range. There are several objections that believers could raise. It could be said that the cat affects not guessing power but fortune and misfortune in real-life situations. I own a black cat, and although she has crossed my path hundreds of times, I see no degradation in my schoolwork or social life. It could be said that the computer's brain is somehow beyond the cat's influence. I see no difference between an object that could land on one of two sides and a stream of electrons that could end in one of two states. Another argument is that the stakes must be raised so that there is a disadvantage to losing. This implies the existence of a malevolent being, manifested in cats, whose reason for existence is to deny people fortune. But that is ridiculous. The idea that black cats cause bad luck is false. Cats do not affect the luck of anyone whose path has been crossed.

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