Volume 1

Experimental psychology : a manual of laboratory practice / by Edward Bradford Titchener.

  • Titchener, Edward Bradford, 1867-1927.
Date:
1901-1905
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Experimental psychology : a manual of laboratory practice / by Edward Bradford Titchener. Source: Wellcome Collection.

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    for holding, keeping its incoming edge precisely parallel to the vertical * black ’ strips. The card is pushed in under the strip, until it hits against the pin-head in the centre of the figure. O, keeping his eyes always upon this pin-head, describes the appearance of the two ‘black’ strips at the moment when the white card emerges from under the strip on Es side of the back- ground. (2) Colour contrast. — Cut pieces of coloured paper, 10 x 7.5 cm. Cut, further, strips of grey paper, 2x1.5 cm. Match the two sets, roughly, paper for paper, as regards brightness ; so that every colour shall have a grey that is, at least approximately, of the same brightness as itself. E lays a matched grey upon a coloured piece, and covers the two with tissue paper. O describes the appearance of the grey as seen through the white tissue. This is repeated, until the whole series has been worked through. We proceed now to a more exact verification of the law, as illustrated by the induction of a grey by a surrounding colour. Materials. — Two colour mixers and discs, the latter 11 cm. in diameter. Rings of black and white paper, 12 mm. in breadth, and 7.5 cm. in (outside) diameter. Protractor. Grey screens. Preliminaries. — Select one of the most saturated colour discs: say the standard red of the series. Place it upon a colour mixer, before a grey background. Choose a grey screen that is approximately of the same brightness as the red. Paste (or pin) a white ring upon the red disc, centring it as accurately as possible. The ring is much lighter than its red background. Paste (or pin) sectors from a black ring over a portion of the white, and set the mixer in rotation. The black and white mix to give a grey ring ; but the grey is, in the present case, tinged with the contrast colour. Is this contrast colour lighter or darker than the red background, or is it of the same brightness ? In either of the two former cases, add or subtract black, until the whole disc (red and contrast ring) is of the same brightness throughout. —We now have an uniformly bright con- trast disc, seen against a grey screen which itself is of approxi- mately the same brightness as the disc.