C. Lloyd Morgan, answered from the texts and cited to the page.
A single striking story proves nothing, for the observer sees what he is disposed to see and the animal's history is unknown. To know how an animal comes to do what it does, you must watch it come to do it — from the first fumbling to the settled habit — under conditions you control. My terrier learned the gate-latch not by insight but by the trial that chanced to succeed; only the watching from the beginning showed it.12345
I tied a piece of string, in later trials, round the centre of balance, but this, at the time of the dog's death, had not served as a sure guide to his experience. The way in which my dog learnt to lift the latch of the garden gate, and thus let himself out, affords a good example of intelligent behaviour. The iron gate outside my house is held to by a latch, but swings open by its own weight if the latch be lifted.Animal Behaviour, pp. 144–145
As it stands, it is quite within the range of sense-experience; nay, more, it affords a very pretty example of the application of sense-experience to new circumstances. It is typically intelligent. One of my own students, Mr Edward J.An Introduction to Comparative Psychology, p. 294
I watched the dog at a very early stage of the development of the habit. He then ran up and down the low wall, and put his head out between the iron bars, now here, now there, now elsewhere, keenly gazing into the road. This he did for quite three or four minutes.An Introduction to Comparative Psychology, pp. 293–294
For how could a chick learn to avoid cinnabar caterpillars if the sight of their black and golden-ringed bodies had not become associated with their distastefulness, and that so intimately and with such a nicety of mechanism that the instinctive tendency to peck at any small object at suitable distance is arrested by the restraining impulse due to the associated taste?Habit and Instinct, p. 153
Mr. E. J. Shellard observed * an act of similar import in a Scotch staghound, which "appeared at first to be the result of thought," but which, on closer observation, was clearly seen to be the result of intelligence in the restricted sense of the ¥ 1c, 21.—Fox-terrier lifting the latch of a gate. term. The dog released the lever-latch of a yard door.Animal Behaviour, p. 146
The demand for controlled observation founded the science and I hold it; where it can err is in the other direction, in mistaking the impoverished laboratory situation for the animal's real capacities, and the naturalists who later watched animals in the field rightly recovered what the controlled study can miss.