Table 1.

Demographic data and psychophysiological parameters of healthy volunteers from London, UK, grouped according to their TCF4 rs9960767 genotype (means and SEMs in parentheses, sex and smoking status in frequency data)

TCF4 rs9960767 genotypeCC + ACAATotalFdf/dferrpdaηp2
n12 (12.2%)86 (87.8%)98 (100%)
Age25.4 (1.7)26.2 (0.7)26.1 (0.6)0.201/970.660.130.00
Years of education17.2 (1.2)17.2 (0.3)17.2 (0.3)0.001/971.000.000.00
Male (%)b33.3%51.2%49.0%10.36
Current smokers (%)b0.0%26.7%23.5%10.06
Current cigarettes smoked per day (only in smokers)9.0 (1.3), n = 239.0 (1.3), n = 23
Fagerström Nicotine Dependence Test (score; only in smokers)1.8 (0.5), n = 231.8 (0.5), n = 23
First block, amplitude of pulse-alone trials (arbitrary units)685 (160)706 (41.9)703 (41.3)0.031/970.870.050.00
Mean amplitude of pulse-alone trials (arbitrary units)523 (117)579 (38.6)572 (36.6)0.251/970.620.150.00
Mean PPI (%; mean across 3 SOA conditions: 30, 60, 120 ms)c14.4% (4.9)32.9% (1.7)30.8% (1.7)12.81/930.0011.070.12
Early habituation of pulse-alone trials (%; between first and second block)25.9% (8.3)19.6% (2.9)20.4% (2.7)0.591/970.450.240.01
Total habituation of pulse-alone trials (%; between first and fourth block)29.2% (11.9)28.9% (3.3)28.9% (3.3)0.001/970.970.010.00
Habituation of pulse-alone trials across 4 blocks (linear gradient coefficient b)−81.3 (28.9)−65.0 (8.6)−67.0 (8.3)0.411/970.520.200.00
  • Bold indicates statistical significance.

  • aEffect size Cohen's d (d = 0.2 is small, d = 0.5 is moderate, and d = 0.8 is a strong effect).

  • bFisher's exact test.

  • cANCOVA, means adjusted by covariates sex and cigarettes per day.