PSY 402 Theories of Learning Chapter 9 – Motivation

Evidence of Motivation  Behavior is variable. Rate of responding changes even in the presence of the same stimuli (the same environment).  Behavior is persistent. Behavior continues once started, even when not rewarded immediately.  Motivation translates knowledge into action – Tolman’s distinction between learning and performance.

Early Studies of Motivation  Deprivation leads to behavior that can be quantified (measured, counted). Deprivation increases motivation.  Specific deprivation leads to specific hungers. Animals and people are more motivated to work for what they need.  Homeostasis – behavior helps the body defend an equilibrium of nutrients.

Hull’s Drive Theory  Hull’s drive theory started simple but added parameters to account for observed behavior.  The first version included just drive (D) and habit (H). Habit is Hull’s term for learning. Drive is motivation Behavior strength = D X H  The terms do not interact.

9.1 Resistance to extinction

Problems with Drive Theory  Drive was hypothesized to increase general activity levels, but did so inconsistently. Hungry and thirsty animals don’t necessarily show more activity of different kinds, than satiated ones. Deprivation affected different species differently.  Hunger and thirst seem to motivate increases in behaviors related to seeking food or water, not all behavior.

9.2 Effects of hunger on various behaviors in the golden hamster (Part 1)

9.2 Effects of hunger on various behaviors in the golden hamster (Part 2)

Incentive Learning  Simple behaviors show a direct connection to deprivation, but more complex behaviors have a more complicated relationship with reward.  Dickinson & Balleine argued that in order for an incentive to be motivating, the animal must know that it will satisfy a state of deprivation. The thirsty rat must drink water and feel better in order for water to become an incentive.

9.3 Lever-pressing for food pellets

9.4 Incentive learning (Part 1) Previous experience increases lever pressing for hungry rats.

9.4 Incentive learning (Part 2) Previous experience decreases lever pressing for satiated rats.

Examples  Baby rats learn that water satisfies thirst and food pellets satisfy hunger.  Rats learn that a heat lamp is uncomfortable in a warm room, then learn that it feels good in a cold room.  Tolman emphasized cathexes – the relationship between a goal and its motivational state (e.g., food and hunger).

Anticipation of Need  Motivated behavior is organized to anticipate need, instead of waiting until there is deprivation. Rats on a high protein diet, over time, drink water before they need to. With 3 meals, when meal 2 is eliminated, rats eat more at meal 3, but gradually shift to eating more at meal 1. Rat stomachs are never empty during free-feeding

9.5 Meal frequency, size, and total (daily) intake As rats must work harder for their food, they have fewer meals but eat more to keep overall intake the same.

Children’s Eating  Newborn babies initially cry to nurse when hungry. By 6 weeks (not months), they learn to eat more when they recognize cues to approaching night, so they begin sleeping through the night.  Preschool kids eat more snacks in rooms associated with food (ice cream), even though satiated. Room cues are CS’s that elicit digestive CR’s.

9.6 Children who are “full” eat more snack food and take less time to begin eating

Food Preferences  Children prefer the foods they eat when they are hungry.  Children can be taught to pay attention to both internal and external cues. Internal = hunger, external = environmental signals such as time of day, signals for food.  Specific hungers for certain foods may be learned too -- the food is associated with feeling better after a deprivation state.

9.7 Old vs. new diet in rats

Anticipation of Reward  Acquired motivation – expectation of reward based on prior experience.  Bait and Switch – animals show disappointment when the expected reward is not there. Monkeys who expect banana but get lettuce are mad. Rats who expect mash but get sunflower seeds run slower.

Contrast Effects  Crespi switched incentives halfway through an experiment. Negative contrast – rats switched from 245 to 16 were slower than those receiving 16 all along. Positive contrast – rats switched from 1 to 16 ran faster than rats receiving 16 all along.  Crespi called these “elation” and “depression” effects because he thought the rats were emotional about the change.

9.8 Running speeds of rats that were given rewards of different sizes Negative contrast Positive contrast

Frustration  Flaherty reduced a 32% sucrose solution to 4% and observed negative contrast in behavior. No stress response occurred until the second day. On the first day, rats licked less but explored their environment, looking for the 32% solution. On the second day, rats became frustrated and upset (judging by corticosteroids).  Tranquilizers abolished the contrast on day 2.

9.9 Successive negative contrast Negative contrast

Hull’s Response  Spence modified Hull’s drive theory to include findings of incentive motivation. K was added to account for incentive. Behavior strength = D x H x K  Drive is innate and internal, incentive is learned and external.  Drive pushes behavior, incentive pulls it.