Bauhaus-Universität Weimar

Dictionary of philosophy and psychology including many of the principal conceptions of ethics, logics, aesthetics ... and giving a terminology in English, French, German and Italian, vol. 1 [a-laws]
Baldwin, James Mark
another electro-magnet draws a pointer to the 
scale and holds it, while the pendulum con¬ 
tinues its course. The position of the pointer 
indicates the reaction time. The chronoscope 
is usually ‘ controlled ’ or verified from time 
to time by a control hammer or electric 
The chronograph used in psychological ex¬ 
periment is some form of revolving cylinder, 
such as the kymograph or polygraph, described 
above (II, general). The time is measured 
by a tuning-fork, metronome, or seconds pen¬ 
dulum, and recorded by means of tambours or 
an electric circuit. The electric tuning-fork 
gives the most accurate results. An electro¬ 
magnet near one prong of the fork draws that 
prong ; this breaks the circuit, and the prong, 
released, flies back, makes the circuit again, 
and so on. The fork is thus kept in vibration, 
and as the circuit is made and broken with 
each vibration, it is recorded on the cylinder 
by the Deprez signal. When the circuit is 
finally broken by the reaction movement, the 
record ceases, though the fork continues for 
a time to vibrate. A continuous time record 
may be obtained by a quill attached to a 
prong of the fork and touching the cylinder. 
In other forms, the record is made by another 
tuning-fork vibrating in £ sympathy.’ 
The reaction-time apparatus includes also 
the stimulus releaser and the reaction hey. 
For visual stimuli, such as light, colours, 
letters, and words, a screen with an aperture 
is attached to a pendulum ; as the latter 
swings, the stimulus, behind it, is exposed for 
a time to view ; the instant this exposure 
begins, the chronoscope or chronograph circuit 
is made. The two apparatus are combined 
in the pendulum chronoscope. Instead of a 
pendulum, a heavy falling screen with an 
aperture may be used to expose the stimulus. 
For sensations of sound a bell or hammer is 
struck, and this contact completes the circuit, 
which starts the time apparatus. For sensa¬ 
tions of touch a blunt point is pressed against 
the skin, and this movement completes the 
The most common form of reaction key is 
for the hand ; it is similar to a telegraphic 
key ; the circuit is broken (or made) by press¬ 
ing a knob at the end of a lever. For reacting 
with the vocal organs a lever is fastened to the 
jaw or pressed against the teeth ; when the 
mouth is opened to speak a circuit is broken. 
In another (Libbey-Baldwin) form the mouth 
is placed at the large end of a funnel ; a puff 
of air is sent through the funnel, moving 
a swinging metal tongue at the other end 
and breaking the circuit. For reaction with 
choice a complex key is used, with a lever for 
each finger ; if one stimulus appears, the thumb 
lever is pressed ; if another stimulus, the fore¬ 
finger lever, and so on, as agreed on before¬ 
hand. Or two simple keys may be used and 
the reaction made with right or left hand 
(2) Least Duration. The least duration of 
stimulus consistent with a given kind of per¬ 
ception is measured as follows : a disk with 
alternate sectors of black and white is rotated 
on a colour-wheel (described above, B. a, (4)) ; 
when the speed is increased beyond a certain 
rate the flickering ceases, and we see a uniform 
grey ; from the rate of speed and width of the 
sectors the duration of the separate stimuli is 
calculated. Or,'using a screen with aper¬ 
ture, attached to a pendulum, and taking a 
printed word as stimulus, the speed of the 
pendulum is increased or the width of the 
aperture diminished till the word is no longer 
distinguishable ; the least time of exposure at 
which the word can be read is thus deter¬ 
mined. Arrangements with auditory limiting- 
stimuli have also been used. 
(3) Time Relations of Different Senses. 
The relation between simultaneous percep¬ 
tions of visual and auditory stimuli is measured 
by the complication pendulum. This consists 
of a disk with a scale, over which swings a 
pointer attached to a pendulum. Concealed 
behind the disk is a bell, which can be adjusted 
so as to sound as the pointer passes any given 
point on the scale. The subject notes the 
point at which the bell seems to sound ; the 
direction and amount of error depends upon 
certain conditions of attention, &c. 
(4) Appreciation of Time. To measure the 
least noticeable difference between two periods 
of ‘ empty ’ time, the time-sense apparatus is 
used. It consists of a disk with circular 
scale. Three levers, which project from the 
disk, may be placed at any points on the scale. 
Another disk, with a single pointer, rotates 
over this, and the pointer strikes the three 
levers in turn, making an electric circuit, and 
causing a bell or hammer to sound each time. 
The position of the first two levers being fixed, 
the third is varied till the time between the 
second and third taps is just noticeably dif¬ 
ferent from the time between the first and 
second. The time-sense apparatus of Schu¬ 
mann is described in Zeitsch. f. Psychol., 
iv. i ff. 
D. Apparatus for investigating the Intellec- 


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