Stereotypies, or the repetition of an invariant sequence of behavior, are a component of normal behavior in humans. Abnormal high rates of stereotypic behavior can be found in a number of handicapped populations like mentally retarded, hearing impaired, blind and autistic people. So far there is no univocal (biological) explanation for these seeming meaningless behaviors. The homeostasis interpretation assumes that there is an optimum level of stimulation and that stereotypy compensates for under- or overstimulating environments. According to the operant condition, stereotypy is maintained by reinforcers. These reinforcers can be either positive, involving some particular sensory input or attention from others, or negative, involving escape or avoidance of aversive stimuli. An alternative explanation suggests that stereotypy is neurobiologically based and neither adaptive nor functional.

Stereotypic behaviors do not form a homogeneous class of behaviors but vary considerably in onset, timing, form, intensity, frequency, cyclicity, variability and sensitivity to environmental change. There are inter-individual differences in conditions eliciting stereotypies and intra-individual differences in the effect situational conditions have on various stereotypies. This suggests that there is unlikely to be a single explanation for stereotypies. We were interested whether we could prove that differences in emotional context of stereotypies lead to differences in form and duration. Secondly we wished to study whether there is a correlation between heart rate changes, emotional context and form of stereotypy. Finally we wanted to study the social context and consequences of stereotypies.

To investigate differences in form and duration, each occurrence of stereotypic behavior was recorded from videotape by means of The Observer (Noldus Information Technology). Mood and form were added as modifiers to the code for stereotypic behaviors. Heart rate was recorded with the Sport Tester PE 3000. One B.P.M. value was calculated every five seconds. Of every occurrence of stereotypic behavior, the heart rate values within one minute surrounding the onset of stereotypic behavior were studied. To evaluate the social context and consequences we detected temporal patterns with the software Theme. The software package developed by M.S. Magnusson [1] recognizes temporal behavior patterns based on consistencies in interval.

The results show that stereotypic behavior should no longer be treated as a homogeneous class of behaviors with one function. The phenomenological division of stereotypic behaviors into those associated with elation, distress and composure was sufficient to reveal significant differences in the mean duration and form of stereotypies and in the pattern of heart rate over time around the onset of stereotypic behavior. Analysis of temporal patterns proved a useful method for analyzing the social context and consequences of stereotypies.

References

1. Magnusson, M.S. (1998). Real-time pattern detection versus standard sequential and time series analysis. This volume.