The Alternation Problem in Animal Psychology

Abstract

1. By glueing the odd numbers of a row of grains to heavy teak boards fowls were trained to perform a true alternation, i.e. to peck every second grain from a standard row of which all fourteen grains were loose. This was achieved after 500-600 training experiments in 17-19 training days. No punishment was used in this method. 2. Claims by other authors that a training to a true alternation can be achieved in a much shorter time could not be confirmed. As such results are not supported by control tests in which all grains were loose, it is probable that in these cases the birds have learnt only to discriminate between fixed, and loose grains. This also applies to the reported training to select every third one from a series of grains. 3. Although the actual training was effected by preventing the birds from eating the odd grains of the row, the result was nevertheless independent of whether the birds started with the first or the second grain. Rows of odd grains and rows of even grains were eaten without any preference. 4. A sudden increase of the distances between the single grains induced the birds in all cases to abandon the alternation, but it returned without any fresh training when the usual distances were used again. A gradual extension or reduction of the distances, however, did not influence the alternation. 5. A similar result was obtained when the distances between the grains in one and the same row were unequal. Here, too, the alternation was kept when the distances increased or decreased gradually. In this case the correct pecking distances could have the ratio 1 : 2 at both ends of the same row thus proving again a high degree of independence of the absolute pecking distance. 6. In most cases a modification of the experimental conditions (e.g. a different colour of the ground surface, or a curved line of grains instead of a straight line) gave negative results, but a ‘spontaneous readjustment’ resulting in alternation took place frequently without any fresh training. 7. The intended use of a moving lid covering parts of the row of grains in order to avoid a training to a figural pattern or to a temporal rhythm proved impracticable as in this case the birds did not resist pecking at every single grain as soon as it became visible. Apparently the moving of the lid relative to the actually motionless grains had the same effect as really moving objects which have proved to be highly attractive to many birds. 8. The pecking rhythm had no decisive influence on the alternation, but any change of the uniform speed of the pecking movements definitely facilitated mistakes. 9. After the successful training to alternation, boards with one fixed and two loose grains (1, 4, 7, 10, 13 fixed) were used for the unsuccessful training to leave every third grain untouched. The result was that the loose grains 3, 6, 9, 12 were not pecked (see p. 147). This proved that only the successful pecking acts were ‘counted’ by the bird. 10. Relearning of alternation after an interruption of more than 5 months resulted in a considerable saving of time: instead of 19 training days (550 experiments) alternation was almost perfectly mastered again by one bird at the second training day (29 experiments) and completely at the fifth training day (99 experiments).