[page 7 of paper handout]
Few people deny that Habituation occurs in humans
Schicatano, EJ and Blumenthal, TD (1994) Caffeine delays habituation of the human acoustic startle reflex. Psychobiology, 22. pp.117-122.
The present experiments were designed to determine whether caffeine (4 mg/kg) modified startle habituation in low and high caffeine users.
Human eyeblink responses were measured in a startle habituation paradigm in which 30 trials of 85-dB broadband noise stimuli with a duration of 50 msec and a rise time of .1 msec were presented. Caffeine delayed the habituation of startle amplitude in both low and high users and produced significant dishabituation in low users. These findings indicate that caffeine disrupts early sensory filtering.
– or jellyfish (or in the threadworm Caenorhabditis elegans)
Johnson, M.C. and Wuensch, KL (1994) An investigation of habituation in the jellyfish Aurelia aurita. Behavioral and Neural Biology 61, pp.54-59
Results from Experiment 1 showed that polyps significantly decreased their responsiveness to both forms of tactile stimulation with 30- s ISI across 60 trials. Response to a novel stimulus indicated that the response decrement had not been due to fatigue. When the ISI was lengthened to 6 min in Experiment 2, response to the probe form of tactile stimulation did not significantly decrease across 20 trials. Using an ISI of 1 min in Experiment 3, response to the probe form of tactile stimulation decreased significantly across 40 trials.
A significant increase in response to the original stimulus (dishabituation) following presentation of a novel stimulus indicated that response decrement was due to habituation or a habituation- like process rather than simple effector fatigue or sensory adaptation.