762 



SCIENCE. 



[N. S. Vol. II. No. 49. 



to the weather on those days can be drawn. 

 Almost nothing could be inferred from any 

 single answer, but the answers taken to- 

 gether give information of a degree of ex- 

 actness which may be defined. We can, 

 however, better consider this matter in con- 

 nection with questions requiring a quantita- 

 tive answer. 



Three questions were asked with a view 

 to learning the ordinary accuracy of obser- 

 vation: "Do chestnut trees or oak trees 

 lose their leaves the earlier in the Autumn?" 

 " Do horses in the field stand with head 

 or tail to the wind?" " In what direction 

 do the seeds of an apple point ?" The ques- 

 tions were all answered correctly more often 

 than incorrectly, but only by a moderate 

 majority. Thus 30 students thought that 

 chestnut trees lose their leaves the earlier 

 in the Autumn, and 21 were of the oppo- 

 site opinion ; 34 students thought that 

 horses in the field stand with tails to the 

 wind, and 19 thought they stand facing it. 

 Thus in only about three cases out of five 

 will a college student answer such a ques- 

 tion correctly. 



Each class of persons would of course 

 have a different index of precision. In the 

 present cases country boys would probably 

 do better, whereas in other directions, as in 

 judging of character, they might not do 

 so well. This opens up an interesting 

 direction for research. Is the ordinary 

 observation of men or women better? of 

 students in classical or scientific courses ? 

 etc. 



The degree of confidence may be noticed. 

 The students were sure their answers were 

 correct in all 34 times, and in these cases 

 they were in fact correct 27 times. They 

 were somewhat or quite doubtful in all 70 

 times, and in these cases were correct 37 

 times, scarcely more than a majority. Their 

 judgment of their own accuracy was there- 

 fore of some value, and the degree of con- 

 fidence can with advantage be taken in 



ordinary testimony. But there is great 

 individual diflerence in this respect. Some 

 observers are nearly always sure that they 

 are right, whereas others whose decision is 

 equally or more likely to be correct are 

 much less confident. In other and more 

 elaborate experiments I have found that 

 when an observer is entirely doubtful, for 

 example as to which of two weights is the 

 heavier, and makes a guess, his guess is 

 more likely to be right than wrong. This 

 opens an opportunity for determining the 

 part played by subconscious inference in 

 the decisions of daily life, as in judging the 

 the character from the face. 



As regards the direction in which the 

 seeds in an apple point, 24 answers were 

 'upward,' or 'toward stem;' 18 'toward 

 center;' 13 'downward,' and 3 'outward.' 

 The reader may be left to decide whether 

 or not he knows in what direction the 

 seeds in fact point, and what information 

 he can obtain from these answers. 



Two questions were asked, the answers to 

 which measure the ordinary accuracy of in- 

 formation: " Was Luther or Michel Angelo 

 born the earlier and by how many years?" 

 "In what year did Victor Hugo die?" 

 Michel Angelo was assigned the earlier 

 year in 29 of the 45 answers. The average 

 of the answers placed his birth 12 years 

 before that of Luther, which is nearly the 

 correct value (8 years). The average de- 

 parture from the correct value was 54 

 years, which measures a considerable degree 

 of ignorance. 



The average assigned the death of Vic- 

 tor Hugo 12 years too early, with an 

 average departure from the true date of 

 13 years. The median would here give a 

 more correct date, as the average is unduly 

 influenced by a few who assigned a very 

 early date. The extreme values, indeed, 

 betray great ignorance. One student 

 thought Hugo died in 1790, another that he 

 is still alive. One student thought that 



