Two Routes to Interoceptive Prioritisation: Dissociating Likelihood Precision and Preference Reweighting in Active Inference
Authors: St John Grimbly, Nicolas Kuske, Evert A. Boonstra, Charel van Hoof, Rowan Hodson, Benjamin Rosman, Ryan Smith, Mark Solms, Jonathan P. Shock
Organizations: Dept. of Mathematics & Applied Mathematics, Univ. of Cape Town, South Africa · Neuroscience Institute, Univ. of Cape Town, South Africa · Delft University of Technology, Dept. of Cognitive Robotics · Laureate Institute for Brain Research, Tulsa, OK, USA · MIND Institute and CSAM, University of the Witwatersrand, South Africa · INRS, Montreal, Canada
An embodied agent must prioritise among competing bodily needs. In active inference, it can respond to an urgent need by increasing the precision of information about that need or by increasing its preference for outcomes that relieve it. We compare these two interventions, separately and together, in a foraging gridworld with three lethal needs, and ask how each changes survival, perception and the body model the agent learns. Precision sharpens interoceptive posteriors and improves survival. Preference reweighting keeps bodily states further from their lethal boundaries and changes the states from which the agent learns, so its learned model covers fewer need levels, with lower quality across all levels but slightly higher quality on the levels it visits. An experiment on 72 further layouts does not establish the predicted preference benefit on difficult layouts, but both interventions improve average survival there and their interaction is positive. Survival alone therefore gives an incomplete account of how a model prioritises needs and learns about its body.
Figures & tables
Figure 1: The foraging task (illustrative, with layouts varying): one food and one water tile on a 6×6 grid. The needs panel (right) tracks three interoceptive levels and their lethal floors. Hunger and thirst decline over time. Drinking restores thirst but lowers oxygen, which recovers only on land. The best priority therefore depends on the current body state.
Figure 2: The perception–action loop and the two implemented mechanisms. Precision ( κ ) sharpens the likelihood A , which feeds inference and planning and governs the body’s emission. Preference reweighting changes C , which enters only the planner’s pragmatic term. The lower boxes show principal internal effects on the original layouts, not effects exclusive to either intervention.
Figure 3: Survival and the internal dissociation. (a) Condition means and layout-bootstrap 95% intervals across eleven layouts and eight seeds. (b) Layout-level signal-to-error ( ∣mean/s.e.∣ ). Bar length is descriptive. Solid bars have 95% intervals excluding zero (Tables 1 , 3 ).
Contrast
Δ survival
95% CI
Holm p
κ -routing vs uniform baseline
+0.27
[0.12,0.44]
0.0176
dynamic- C vs uniform baseline
+0.11
[−0.06,0.27]
0.248
κ -routing+dynamic- C vs uniform baseline
+0.38
[0.18,0.56]
0.0176
Table 1: Survival contrasts on the eleven original layouts with eight paired seeds. Intervals are paired layout bootstraps. The p values use exact layout-level sign flips with Holm adjustment across the three contrasts.
Comparison
Effect
95% CI
p
Preference, difficult layouts (primary)
−0.008
[−0.025,+0.016]
0.5793
Precision, all layouts (secondary)
+0.111
[+0.076,+0.147]
<0.0001
Preference, all layouts (secondary)
+0.080
[+0.046,+0.118]
<0.0001
Interaction, all layouts (secondary)
+0.114
[+0.049,+0.182]
0.002
Table 2: Survival effects in the additional experiment. The primary test uses the 24 layouts calibrated as difficult. Secondary effects average over all 72 layouts. Intervals resample layouts. Secondary p values are Holm-adjusted jointly with the continuous difficulty test.
Metric (vs. baseline)
κ -routing
dynamic- C
κ -routing+dynamic- C
Posterior entropy ( 10−3 )
−1.37[-1.95,-0.84]
−0.26[-0.83,0.28]
−1.18[-1.77,-0.58]
Visited-state entropy
+0.00[-0.09,0.07]
−0.05[-0.14,0.02]
−0.15[-0.24,-0.08]
Minimum headroom
+0.01[-0.02,0.04]
+0.05[0.01,0.09]
+0.11[0.07,0.15]
Table 3: Internal contrasts against baseline, shown as mean [layout-bootstrap 95% CI]. Entropies use 10−3 nats (posterior) and nats (visited state). Headroom is a fraction.
Biological systems must regulate competing needs under limited perceptual bandwidth, where sharpening one estimate costs the capacity to sharpen the others. Any fixed-budget system therefore has to decide where to allocate its perceptual precision. We study this in a foraging agent that must keep several bodily needs satisfied to survive, modelled with active inference. At each step it reads its own body-state beliefs, identifies the most-needed channel, and reallocates a fixed budget of interoceptive precision toward it, so that the same precision-shaped likelihood feeds both belief update and planning. In AffectWorld, a four-channel foraging gridworld, this selective allocation more than doubles learning-phase survival at matched budget against a uniform-precision agent (0.414 vs 0.199 across 11 layouts, n=32 seeds each, paired cluster-bootstrap p≤10−4). Two further results sharpen the mechanism. The benefit runs through planning as well as perception, since denying the shaped likelihood to the planner alone removes about half of it. It is also need-aligned, since aiming precision at the least-needed channel does worse than spreading it evenly. The attended channel additionally learns its own dynamics about twice as fast, and stays ahead even at matched observation count, a behavioural trace of the same precision routing, visible in learning speed, not survival.
St John Grimbly, Nicolas Kuske, Evert A. Boonstra +7
Dept. of Mathematics & Applied Mathematics, Univ. of Cape Town, South Africa · Neuroscience Institute, Univ. of Cape Town, South Africa · MIND Institute and CSAM, University of the Witwatersrand, South Africa +3
Intrinsic motivation plays a central role in adaptive and goal-directed behavior by conferring agents reward-independent objectives and biases useful to act in noisy and uncertain environments. Active Inference addresses the problem of acting in a partially observable environment through a principled framework for belief updating and action selection. A key component of Active Inference is the specification of prior preferences, which shapes behavior by encoding desirable future outcomes. An intrinsic motivation approach called the Maximum Occupancy Principle (MOP) proposes that agents act so as to maximize occupancy over future paths of states and actions, with no preferences or epistemic targets. Despite its simple formulation, MOP gives rise to rich and adaptive behaviors that combine exploratory variability with goal-directed dynamics. In this work, we extend MOP to partially observable environments and introduce a Bellman reformulation of the Expected Free Energy for Active Inference, both incorporating belief-based inference over hidden states as part of the agent state. The Bellman formulation enables tractable offline computation via value iteration over the full belief-state space. We compare the resulting behaviors in a set of minimal experimental settings with uncertain food sources. We find that MOP agents switch between goal-directed (food seeking) behavior and exploration between different food sources, depending on their energy available and their belief state. In contrast, Active Inference agents mostly inhabit regions around a single food source, a strategy having both high pragmatic and epistemic value. We finally compare with Empowerment, which is shown to be qualitatively similar to Active Inference.
Manolis Mylonas, Rubén Moreno Bote
Center for Brain and Cognition & Department of Engineering Universitat Pompeu Fabra Barcelona, Spain
Reward learning typically assumes the human's input covers everything that matters for the task. In practice, humans can only attend to so much at once, so their teaching naturally captures some features---or aspects of the task---better than others. Prior work has shown how the robot can identify which features were poorly supervised directly from its teaching data. But the current solution is to ask the human to try again, putting the burden on someone who already struggled to convey those features. We propose shifting this burden to the robot. Our key insight is that the same information that tells the robot what it doesn't know can help it ask better questions. Preference queries offer a low-effort channel for resolving this uncertainty, but only if the robot knows where to direct them and the human knows what to attend to when answering. We act on this insight in two ways: we build an informed prior that targets preference queries at the features that need resolving, and we accompany each query with an explanation that focuses the human's attention on exactly those features. In simulation, the informed prior beats the standard active preference learning baseline by up to 30.8% in the low-query regime, where reducing human effort matters most. In a user study, the informed prior and explanations each significantly improve reward recovery and amplify each other.