Choosing Between Predictable and Unpredictable Shock Conditions: Data and Theory

Reviews the literature on predictability and describes the factors that affect choice. Emphasis is given to the reliability of basic findings, including replications and failures to replicate. Behavioral measures related to choice are reviewed, and some physiological correlates of predictable and unpredictable shock are noted. The data allow several firm conclusions regarding preference, notably that (a) rats (albino, hooded, male, female) prefer predictable shock conditions; (b) they prefer predictable conditions whether shock is avoidable, escapable, or inescapable and whether it is scrambled or unscrambled grid shock; (c) this preference occurs with different procedures, apparatus, and shock delivery systems, such as water electrodes or electrodes attached to the tail, back, ears, or pubis bone; (d) fish and birds also prefer the signaled condition; and (e) although the preference is robust, it is affected by shock intensity, signal duration, intershock intervals, amount of training, and the dependability of shock-free periods. Other factors that may affect preference are also noted. Finally, the theoretical views of conditioned reinforcement, of information, of preparation, and of safety are evaluated, and their strengths and weaknesses are described