Behavioural Brain Research 261 (2014) 49–55 Contents lists available at ScienceDirect Behavioural Brain Research j ourna l h om epage: www.elsevier.com/locate/bbr Review Behaviorally inhibited individuals demonstrate significantly enhanced conditioned response acquisition under non-optimal learning conditions J.L. Holloway a,b , M.T. Allen b,c , C.E. Myers b,d , R.J. Servatius a,b,d,∗ a UMDNJ-GSBS, Newark, NJ, USA b Stress and Motivated Behavior Institute, NJMS-UMDNJ, Newark, NJ, USA c University of Northern Colorado, Greeley, CO, USA d Neurobehavioral Res. Lab. (129), DVA Med. Center, NJHCS, East Orange, NJ, USA h i g h l i g h t s • Behavioral inhibition is a known risk factor for anxiety disorder development. • Inhibited individuals demonstrate enhanced conditioned eyeblink response acquisition. • Enhancements were greater under non-optimal relative to full-reinforcement paradigms. • Motivational aspects of uncertainty or general potentiation may influence etiology in BI. a r t i c l e i n f o Article history: Received 24 February 2013 Received in revised form 17 October 2013 Accepted 24 October 2013 Available online 23 November 2013 Keywords: Classical conditioning Temperament Anxiety Predictability a b s t r a c t Behavioral inhibition (BI) is an anxiety vulnerability factor associated with hypervigilance to novel stimuli, threat, and ambiguous cues. The progression from anxiety risk to a clinical disorder is unknown, although the acquisition of defensive learning and avoidance may be a critical feature. As the expression of avoidance is also central to anxiety development, the present study examined avoidance acquisition as a function of inhibited temperament using classical eyeblink conditioning. Individuals were classified as behaviorally inhibited (BI) or non-inhibited (NI) based on combined scores from the Adult and Ret- rospective Measures of Behavioural Inhibition (AMBI and RMBI, respectively). Acquisition was assessed using delay, omission, or yoked conditioning schedules of reinforcement. Omission training was iden- tical to delay, except that the emission of an eyeblink conditioned response (CR) resulted in omission of the unconditioned airpuff stimulus (US) on that trial. Each subject in the yoked group was matched on total BI score to a subject in the omission group, and received the same schedule of CS and US deliv- ery, resulting in a partial reinforcement training schedule. Delay conditioning elicited significantly more CRs compared to the omission and yoked contingencies, the latter two of which did not differ from each other. Thus, acquisition of an avoidance response was not apparent. BI individuals demonstrated enhanced acquisition overall, while partial reinforcement training significantly distinguished between BI and NI groups. Enhanced learning in BI may be a function of an increased defensive learning capacity, or sensitivity to uncertainty. Further work examining the influence of BI on learning acquisition is important for understanding individual differences in disorder etiology in anxiety vulnerable cohorts. Published by Elsevier B.V. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 2. Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 2.1. Participants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 2.2. Materials and apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 2.3. Psychometric scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 ∗ Corresponding author. E-mail address: Richard.servatius@va.gov (R.J. Servatius). 0166-4328/$ – see front matter. Published by Elsevier B.V. http://dx.doi.org/10.1016/j.bbr.2013.10.041