An affordance analysis of unconditioned lever pressing in rats and hamsters

Operant Behavior: Responses that occur independently of identifiable stimuli (Skinner, 1938).
Unconditioned Responses: Behaviors emitted prior to conditioning are termed unconditioned; these represent the operant level of behavior.
Historical Context: Limited past research on operant-level responding; mostly focused on lever pressing decades ago (Bullock, 1950; Segal, 1959).
Importance of understanding unconditioned responses as part of organismal activity (Baron et al., 1961).

Objective: Assess how lever height affects unconditioned pressing behavior in rats and hamsters.
Hypothesis: Different lever heights should provide varying postural support, influencing frequency and duration of lever pressing.

Subjects: 42 male Wistar rats, aged 180 days (weights: 340-375 g).
Apparatus: 8-sided operant chamber; lever height variations: 30, 72, 114, 156, 198, 240 mm.
Procedure: Rats divided into six groups based on lever height; 30-minute sessions carried out.
Measurements: Body dimensions recorded to assess lever height relative to body size.

Lever Height Influence: Significant effect on response rate; maximum pressing observed at 156 mm and 30 mm compared to other heights.
Response Behavior: Engagement characterized by bouts, interspersed with pauses, accurately described by a mixture of exponential distributions.
Analyzing Inter-Response Times (IRTs): Organization of pressing into bouts, with different heights influencing initiation and duration of press bouts.

Subjects: 14 male golden hamsters, similar housing and diet conditions.
Apparatus: Similar chamber used, with four lever heights (30, 72, 114, 156 mm).

Lever Height Influence: Proportion of responses peaked at 114 mm; latency to first press was shortest at 114 mm and longer at 156 mm.
Statistical Analysis: ANOVA demonstrated significant differences based on lever height.

Affordances: Objects (levers) afford actions based on their dimensions relative to organism size (Warren, 1984).
Intrinsic Metrics: Analysis reveals that both rats and hamsters pressed more frequently at heights just below their maximum reach with forepaws.
Behavior Organization: Pressing grouped into bouts, imitating reinforced responding patterns.
The findings suggest lever height significantly influences exploratory behavior and operational response rates.

Provides insights into operant-level responding in non-human animals, potentially translating to human behaviors (e.g., children exploring objects).
Recommendations for ergonomics in workspace design to consider body dimensions in action planning (Choi et al., 2007).

Lever height directly correlates with response frequency in both rats and hamsters, showcasing the significance of postural support in unconditioned operant behavior.
Findings contribute to the understanding of how physical environments affect behavior, demonstrating a need for further exploration of affordance in behavioral research.