Hunziker, M. H. L., Saldana, R. L., & Neuringer, A. (1996).
Behavioral variability in SHR and WKY rats as a function of rearing environment and reinforcement contingency.
Journal of the Experimental Analysis of Behavior,
65, 129-144.
The spontaneously hypertensive rat (SHR) may model aspects of
human attention deficit hyperactivity disorder (ADHD). For
example, just as responses by children with ADHD tend to be
variable, so too SHRs often respond more variably than do
Wistar-Kyoto (WKY) control rats. The present study asked whether
behavioral variability in the SHR strain is influenced by rearing
environment, a question related to hypotheses concerning the
etiology of human ADHD. Some rats from each strain were reared in
an enriched environment (housed socially), and others were reared
in an impoverished environment (housed in isolation). Four groups
- enriched SHR, impoverished SHR, enriched WKY, and impoverished
WKY - were studied under two reinforcement contingencies, one in
which reinforcement was independent of response variability and
the other in which reinforcement depended upon high variability.
The main finding was that rearing environment did not influence
response variability (enriched and impoverished subjects
responded similarly throughout). However, rearing environment
affected body weight (enriched subjects weighed more than
impoverished subjects) and response rate (impoverished subjects
generally responded faster than enriched subjects). In addition,
SHRs tended to respond variably throughout the experiment,
whereas WKYs were more sensitive to the variability
contingencies. Thus, behavioral variability was affected by
genetic strain and by reinforcement contingency but not by the
environment in which the subjects were reared.
Key words: behavioral variability, response sequences, attention
deficit hyperactivity disorder, body weight, response rate,
environmental enrichment, deprivation, spontaneously hypertensive
rats