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Habituation as discussed by Humphrey in The Nature of Learning (1933)

A shadow thrown on sea urchin makes it raise its spines; but if the stimulus is repeated 3 or 4 times visible reaction ceases. This has been called ‘aclimatisation’, ‘accommodation', or ‘negative adaptation’ and is an example of characteristic biological equilibrium.

Habituation is ubiquitous: it is found in amoeba and other single-celled animals; hyrda, sea anemones worms, parasitic grubs, barnacles, larva of mosquitos bivalve molluscs, snails. (water snails under trees moving in wind ignore shadows, but the same species where no trees very reactive.) many vertebrates and insects; (cows on railway embankments; humans living in cities don’t notice traffic noise.)

BUT NOT ALL SPECIES USE THE SAME mechanism – apparent habituation can be found in species with no nervous system. It can be in receptor systems, or ‘central’.

An Experiment (Humphrey, 1933 p 136)

  • Land snails on an oak platform 18x5in – on ball bearings.

  • Electrically produced jerks given at regular intervals, usually 2 secs.

  • The response measured was withdrawing into the shell.

  • There were individual differences. After habituation one snail did not react to the blow of hammer on the board, and some would be half on the board and half on the table, and still not react when the board was jerked.

  • If these snails were given half-min rests then the response re-appeared, but with repeated half-min rests there is longer term habituation.

  • The phenomena cannot be attributed to fatigue since a new stimulus e.g. a steel ball dropped on the board, will produce the response.


Habituation is distinguishable from response fatigue in a physiological sense in this instance, but not always, especially if no nervous system.

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Thompson and Spencer (1966) Used hindlimb flexion reflex of the acute spinal cat, and list 9 characteristics of habituation they found.

1. Repeated stimulation decreased response.

2. Then no stimulation spontaneous recovery over time.

3. If 1. & 2. repeated habituation becomes quicker (long term Habituation)

4. More frequent stimulation more rapid habituation

5. Weaker stimulation more rapid or stronger Habituation

6. Further stimulation after Habituation delayed recovery of response.

7. Habituation generalizes to similar stimuli.

8. A separate stimulus response recovery (=dishabituation).

9. If 8. repeated dishabituation disappears.

Pinsker et al (1970)

Used the sea-slug Aplysia: gill withdrawal reflex in response to a jet of seawater - this habituated over 10 trials at 3-min intervals.

Results - 6 of the above 9 characteristics were found; missing 3, 6 & 7. (with shorter inter-trial intervals, 3. can sometime be observed - Castellucci and Kandel, 1976)

The Mechanism in Aplysia is that sensory pre-synaptic terminals release progressively less neurotransmitter, and this produces decrements in the excitatory post-synaptic potentials (EPSPs). When there is dishabituation, this is because activity of the sensory pre-synaptic terminals is facilitated. (Castellucci and Kandel, 1976; Kandel, 2001).

Sokolov (1975: see Gray, 1976, p.6 and Walker, 1987, p.39-41, or Green 1987, chapter 7) [page 5 of handout]

Sokolov studied adult human Ss. Uses the term “extinction of the orienting reflex” to refer to habituation. The orienting reflex is not modality specific (up to a point) but a generalised response to novelty. It is measured by –

1. Increased sensory sensitivity (and attention?)

2. Drop in skin resistance (GSR)

3. Reduced alpha rhythms in the EEG

4. Constriction of peripheral blood vessels.

5. Cephalic vasodilation (opposite to 4. in the head.

6. Lowering of respiration and pulse rates.

These things don’t happen to an habituated stimulus.

Human Ss show the ‘missing stimulus effect’: there is dishabituation if a stimulus is absent in a normally regular sequence. This shows some kind of pre-attentive extrapolation from previous experience. Habituation in human subjects is related to attention and memory.

Habituation in Pre-Verbal Human Infants

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(see also Year 2 course in Developmental Psychology)

For visual stimuli direction of gaze can be monitored by independent observers or video cameras
For auditory stimuli, measures such as heart-rate deceleration or general movement can be taken. (see Gleitman, Fridlund and Reisberg, 2004. p. 479-80 or Gleitman et al. (1999) p. 554 or Gleitman 1995, p. 512-3)

Cornell (1974)
Ss 5-mo olds shown photos of faces, 6 times, 110-s each time. They lose interest over 6 trials but are aroused when a different face is first used.

Bundy et al (1982)
Ss= 4 months sensitive to changes in simply melodies but only when fundamental and first three harmonics present.

Kellman & Spelke (1983)
In 6 experiments, 224 3-4 mo olds were habituated to 1 object whose top and bottom were visible but whose center was occluded by a nearer object. They were then tested with a fully visible continuous object and with 2 fully visible object pieces with a gap where the occluder had been. Patterns of dishabituation suggested that infants perceived the boundaries of a partly hidden object by analyzing the movements of its surfaces: Infants perceived a connected object when its ends moved in a common translation behind the occluder. (See Gleitman et al., 1995/1999/2004; p. 513/554/480)

Habituation techniques are often used to investigate more elaborate cognitive functioning in human infants. E.g.:

Csibra, G. (2001).
8 month olds perceive illusory contour (Kanizsa) figures as occluding surfaces.

Csibra, G. (2003)
9 and 12 month olds perceive moving dots as agents trying to achieve goals.