In 2004, using the memorable experiment above, psychologists Daniel Simons and Christopher Chabris showed that when viewers are concentrating on a task they can become functionally blind to unexpected objects and events.

Remarkably, Cambridge-based parapsychologist A.D. Cornell had earlier demonstrated a similar effect in an even stranger experiment. In 1959 he dressed up in a white sheet and “haunted” a cow pasture near King’s College; none of approximately 80 passers-by seemed to notice anything at all. When he moved the “ghost walk” to the graveyard of St Peter’s Church, 4 of 142 people gave any clear indication of having seen the “experimental apparition,” and none of them thought they’d seen anything paranormal. (One saw “a man dressed as a woman, who surely must be mad,” one saw “an art student walking about in a blanket,” and two said “we could see his legs and feet and knew it was a man dressed in some white garment.”)

The following year Cornell again dressed as a ghost and passed twice across the screen in an X-rated cinema. 46% of the respondents failed to notice his first passage, and 32% remained completely unaware of him. One person thought she’d seen a polar bear, and another reported a fault in the projector. Only one correctly described a man dressed in a sheet pretending to be a ghost. Cornell concluded that the number of “true” hauntings may be grossly under-reported.

(A.D. Cornell, “An Experiment in Apparitional Observation and Findings,” Journal of the Society for Psychical Research 40:701, 120-124; A.D. Cornell, “Further Experiments in Apparitional Observation,” Journal of the Society for Psychical Research 40:706, 409-418.) (Thanks, Elizabeth.)

“Is the old maxim true about there being an exception to every rule? Well, no doubt we can all think of rules that appear to have no exceptions, but since appearances can be deceiving, maybe the old maxim is true. On the other hand, the maxim is itself a rule, so if we assume that it’s true, it has an exception, which would be tantamount to saying that there is some rule that has no exception. So if the maxim is true, it’s false. That makes it false. Thus we know at least one rule that definitely has an exception, viz., ‘There’s an exception to every rule,’ and, although we haven’t identified it, we know that there is at least one rule that has no exceptions.”

— David L. Silverman, Word Ways, February 1972

Raymond Smullyan used to send emails to friends that read, “Please ignore this message.”

“I don’t like writers who are making sweeping statements all the time. Of course, you might argue that what I’m saying is a sweeping statement, no?” — Jorge Luis Borges, quoted in Floyd Merrell, Unthinking Thinking, 1991

Mistaken reports received by the SPCA on the British island of Guernsey:

• A call to a sick seal on a beach was in fact a duvet
• Also a possible dead dog on a beach was another duvet
• An injured crow was a black bag
• A stray pug was called in and was in fact a frog
• A dead gull hanging from a fence was a carrier bag
• An injured bird was a blonde wig
• Birds of prey often turn out to be pigeons
• A hedgehog rescue once turned out to be a pine cone
• A pregnant cat turned out to be a neutered male
• A call for a shark in trouble was a fish

In June 2016 a member of the public brought in a “dead cat” that turned out to be a dog puppet (“a very muddy, wet, insect covered, cold, collapsed small dog with an injured nose”).

“Both the finder and I were extremely relieved and where an air of sadness had been at the GSPCA it soon turned to laughter,” said SPCA manager Steve Byrne.

They advertised for the owner on Facebook, but I don’t know that anyone ever responded.