reward-valuation-vlm-anhedonia-causal

name	reward-valuation-vlm-anhedonia-causal
description	Mechanistic framework identifying reward-anticipatory units in Vision-Language Models (VLMs) that parallel Nucleus Accumbens (NAc) function. Causal perturbation of NAc-selective units induces anhedonia-like behavioral shifts toward low-effort, low-reward options. Validates alignment between AI reward circuits and human dopaminergic reward system.
activation	reward valuation, VLM anhedonia, Nucleus Accumbens, causal perturbation, reward anticipation, effort-based decision making, dopamine, motivational deficit, depression model
tags	["neuroscience","vision-language-models","reward-system","anhedonia","causal-analysis","NAc","dopaminergic","depression"]
version	1.0.0
author	agent
arxiv_id	2607.06626
paper_title	Reward Valuation in Vision Language Models: Causal Mechanisms Underlying Anhedonia

Reward Valuation in Vision-Language Models: Causal Mechanisms Underlying Anhedonia

Core Innovation

Problem

Recent Vision-Language Models (VLMs) capture increasingly complex aspects of human cognition. However, whether this alignment extends to reward valuation remains unclear. In the brain, anhedonia (loss of pleasure/motivation) is linked to dysregulation in the Nucleus Accumbens (NAc) and dopaminergic reward system.

Challenge: Neuroimaging has localized reward deficits, but establishing causal links between specific neural activity and behavioral symptoms remains difficult.

Solution

Use neuroscience-inspired approach to:

1. Functionally identify reward-anticipatory units in VLMs
2. Test causal role via targeted perturbations
3. Validate alignment with human anhedonia mechanisms

Methodology

Step 1: Identify Reward-Anticipatory Units

Clinical Tests for Anhedonia
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Extract NAc activation patterns
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Search for analogous units in VLM
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Identify "NAc-selective units"

Approach:

• Use clinical tests developed to evaluate anhedonia in major depressive disorder
• Map NAc activity patterns to VLM internal representations
• Identify units that respond specifically to reward anticipation

Step 2: Causal Perturbation

Baseline VLM Behavior
         ↓
Perturb NAc-selective units
         ↓
Observe behavioral changes
         ↓
Compare with human anhedonia symptoms

Perturbation Types:

• Ablation (zero activation)
• Amplification (increase activation)
• Suppression (decrease activation)

Step 3: Behavioral Validation

Test whether perturbed VLM exhibits:

• Shift toward low-effort, low-reward options
• Preservation of task capability (not general impairment)
• Alignment with clinical anhedonia scales (DARS, MAP-SR)

Key Findings

1. Causal Effect of NAc Perturbation

• Perturbing NAc-selective units induces behavioral effects mirroring human anhedonia
• Model shifts toward low-effort, low-reward options in effort-based decision-making tasks

2. Specificity of Deficit

• Not a general capability loss: Perturbed model maintains baseline performance when reward-based choice is removed