NOTES ON HABITUATION
[top of page 4 of handout]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.)
An Experiment (Humphrey, 1933 p 136)
Habituation is distinguishable from response fatigue in a physiological sense in this instance, but not always, especially if no nervous system.
[bottom of page 4 of handout]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 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
(see also Year 2 course in Developmental Psychology)
For visual stimuli direction of gaze can be monitored by independent observers or video cameras
Bundy et al (1982)
Kellman & Spelke (1983)
Habituation techniques are often used to investigate more elaborate cognitive functioning in human infants. E.g.:
Csibra, G. (2001).
Csibra, G. (2003)