Habituation of Exploratory Behavior in Rats - Conditioning and Learning in Psychology

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Abstract

This study investigated the effects of displaced objects and spatial reorganization on habituation of exploratory behavior. The subjects, rats, each individually spent 5 minutes in an open field for 6 trials. Throughout the study, exploratory behavior was measured in the number of contacts the subject made, the number of ambulations, and contact time (seconds). Trials 1-5 were mainly used to familiarize the subject with its surroundings, naturally leading to decreasing amounts of exploratory behavior. Trial 6 involves the same routine, except displaced objects are introduced in an attempt to renew exploratory behavior and promote the building up of environmental maps and representations. Additionally, the measured behavior served as a way to compare individual trials with the averages across the experiment. Specifically, in a combined study of 24 rats, the resulting mean number of contacts, ambulations, and contact time at least either suggested exploratory behavior was renewed or guaranteed it. Hence, the results supported the hypothesis that spatial reorganization of familiar objects can renew exploratory behavior, despite time spent in the habituation phase.

Habituation of Exploratory Behavior in Rats Regarding Spatial Rearrangement

of Familiar Objects

This experiment investigated the possibility of renewed exploratory behavior under the influence of spatial rearrangement, specifically after periods of habituation. Rats are very inclined to explore all aspects of novel environments that they are freshly exposed to, but eventually habituation (or familiarity) overpowers and deadens the urge to explore. However, several studies have investigated the role that spatial arrangements play in the renewal of exploratory behavior. The results of one study in particular confirmed that when using exploration as an index of spatial knowledge, hamsters were likely to reinvestigate objects during a test-session if, after two sessions of habituation, the spatial relationships between these objects were changed (Poucet, Chapuis, Durup & Thinus-Blanc, 1986; Thinus-Blanc, Bouzouba, Chaix, Chapuis, Durup & Poucet, 1987).

Additionally, correlations between the effect of age on object exploration, habituation, and the actual responses to spatial and nonspatial changes were examined (Shukitt-Hale, Casadesus, Canturi-Castelvetri, and Joseph, 2001). Much like our present experiment, Shukitt et al. (2001) rearranged the spatial locations of the objects after both the young and senescent rats were familiarized with the original setting. Their results implied that detection of spatial change in familiar environments does indeed decrease with age, but general exploratory behavior towards novel objects remained the same regardless of the rats’ ages. It was also implied that younger rats responded to both spatial and nonspatial changes by spending more time exploring the displaced objects and the substitute. However, senescent rats were solely capable of detecting nonspatial changes (Shukitt et al, 2001).

In another study, Poucet, Durup, and Thinus-Blanc (1988) gathered data that compared the “between-session” and “within-session” habituation in hamsters, rats, and gerbils. They hypothesized that results of habituation may vary or can be dependent on the type of species being assessed on single sessions verses successive sessions. In other words, they discovered that habituatory patterns of rats were on one end of the spectrum whereas the hamsters and gerbils were on the opposite end. Figuring out which side they would end up on was dependent on whether the between-session or within-session habituation was being considered (Poucet et al., 1988). The results gave light to the notion that individual species may be adaptively utilizing individual patterns of exploration. Thus, it seems inaccurate to base results of exploratory renewal on the overall amount of exploratory activity –...
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