DYNAMOGENIC INFLUENCE OF LIGHT 357 



The stimuli were prepared as follows : Four holes, about 4 mm. 

 in diameter, were perforated in the cards, to form a quadrilateral 

 whose diagonals lay vertically and horizontally and intersected 

 in the center of the card. The figures thus formed were as 

 follows : 



1. A " large" square, whose diagonals were 50 mm. 



2. A "small" square, whose diagonals were 30 mm. 



3. A "wide" rhombus, whose vertical diagonal was 30 mm. and 

 its horizontal diagonal 50 mm. 



4. A "tall" rhombus, whose vertical diagonal was 50 mm. and 

 its horizontal diagonal 30 mm. 



The figures were designated by the adjectives enclosed in quo- 

 tation-marks. The subject was instructed to "feel" each card 

 separately and lay it in one of four piles conveniently spaced from 

 left to right in the order given above, and to speak, subvocally, 

 the name of the figure as soon as he determined it. The rhyme 

 occurring in the names of the piles when arranged in order proved 

 to be a useful mnemonic in the early stages of learning. 



During all of the work, the subject wore a pair of special chauf- 

 feur's goggles, hinged at the nosepiece and with a covering of 

 plush over the framework which fitted closely to the subject's 

 face. The lenses were unusually large and covered the whole 

 of the visual field when the subject's gaze was not extremely 

 oblique. The lenses were thick and were sand-blasted so that 

 they formed almost perfect diffusers. They were kept clean by 

 the application of alcohol. It was impossible to distinguish any 

 objects through them, or indeed to detect gross differences in 

 brightness of objects placed farther than 20 cm. from the eye. 



The subject was required to hold the head in an easy position, 

 tilted slightly backward, with the muscles of the neck relaxed, 

 and to look horizontally through the lenses toward a white- 

 washed wall about 80 cm. from the eyes. The table on which 

 the cards were to be sorted was also covered with heavy card- 

 board heavily sized with baryta. 



The work was done under two compared conditions: (1) with 

 the room in total darkness, except for a slight leakage about the 

 frames of the openings in it; and (2) with the room lighted in such 



