Conceptual priming in a generative problem-solving task

Three experiments explored how participants solved a very open-ended generative problem-solving task. Previous research has shown that when participants are shown examples, novel creations will tend to conform to features shared across those examples (Smith, Ward, & Schumacher, 1993). We made the shared features of the examples conceptually related to one another. We found that when the features were related to the concept of hostility, participants' creations contained hostile features that were not part of any of the examples. These results suggest that participants will design novel entities to be consistent with emergent properties of examples shown to them. We also found that a mild hostility prime from unscrambling sentences had a similar conceptual effect. Together, the two effects suggest that conceptual priming of generative cognitive tasks will influence the cognitive aspects of the creative process.

The inadvertent use of prior knowledge in a generative cognitive task

In four experiments with 332 participants, participants were asked to generate novel nonwords for English categories. When participants were shown examples embedded with regular orthographic structures, participants' nonwords tended to conform orthographically to the examples, despite instructions to avoid using features of the examples. The effect was found with immediate testing (Experiments 1) and delayed testing (Experiment 2). The effect was also found with arbitrary features (Experiments 1-4), as well as with naturally occurring orthographic regularities (Experiment 4). Participants had difficulty avoiding the use of this prior knowledge, despite being able to list the features they were asked to avoid (Experiment 3). The results are discussed in terms of the inadvertent use of prior knowledge in generative cognitive tasks.

Topographic differences in CNV amplitude reflect different preparatory processes

Topographic differences in Contingent Negative Variation (CNV) were recorded while people were preparing for cognitive versus motor tasks in an S1-S2 paradigm. CNV had a frontal distribution when people prepared to encode words into long-term memory, whereas CNV was more centrally distributed when the tasks were predominantly motoric. These topographic differences appeared to be related to the type of task rather than the amount of information extracted from the S2, because a direct manipulation of the level of S2 processing had little effect on CNV amplitude. The topographic differences in CNV suggest that preparation for motor activity is a different psychological process from preparation for stimulus processing and that these two processes are subserved by different neural structures. This experiment also demonstrated that a recognition memory paradigm can be useful in the investigation of the psychological correlates of CNV.

Activation patterns and length changes in hindlimb muscles of the bullfrog Rana catesbeiana during jumping

We measured the electromyographic (EMG) activity of seven hindlimb muscles during jumping in the bullfrog Rana catesbeiana. The semimembranosus, gracilis major, gluteus magnus, adductor magnus, cruralis and plantaris longus were consistently active approximately 20-40 ms before any perceptible movement, as indicated by simultaneous video recordings. Activity ended before full extension of the hindlimb and take-off. Activity in the semitendinosus was variable among the jumps recorded. Simultaneous measurements of EMG activity and length changes (via sonomicrometry) in the semimembranosus (SM) and gluteus magnus (GM) muscles indicated that the performance characteristics of these two muscles differed. The SM muscle (a hip extensor) shortens and is activated in a manner consistent with its producing power during a significant fraction of the take-off phase. It shortened by a mean of 26.2% of the resting length during the propulsive phase of the two longest jumps for each frog. The delay between the onset of EMG activity and the beginning of shortening averaged 24 ms, which was brief compared with that found for the GM. The total strain and mean shortening velocity of the SM increased with jumping distance. Contrary to our initial expectations, the GM muscle does not shorten as one would expect of a muscle involved in powering the jump throughout take-off. This muscle has an extensor action at the knee, but also has a flexor action at the hip. A long delay existed between the onset of EMG activity and the beginning of shortening (46-116 ms among the individuals tested). Shortening during take-off by the GM (a mean of 16.7% for all jumps) was much less than by the SM, and in many jumps most of this shortening occurred late in the take-off period. Although the GM cannot contribute directly to power output early in take-off, it may contribute to powering the jump indirectly by transferring energy from the hip extensors to the knee joint. We conclude that muscles previously assumed (on the basis of anatomical criteria) by ourselves and others to be powering the jump may show considerable diversity of function. We hypothesize that elastic energy storage is used to help power jumping, and therefore suggest that muscles in series with major tendinous elements should be targeted for further study.

A decrement-to-familiarity interpretation of the revelation effect from forced-choice tests of recognition memory

In the revelation effect, the probability of labeling a target or a lure as "old" on item recognition tests increases if just prior to their recognition judgment, participants first identify a disguised version of the test item. The same occurs with interpolated tasks that occur just prior to a recognition judgment if the task shares constituents with the test items. One explanation of this test bias is an increased feeling of familiarity that comes from the identification stage preceding the recognition judgment (e.g., D. C. LeCompte, 1995; C. R. Lou, 1993). This study's finding in 4 experiments that 2-alternative forced-choice recognition either yields no effects of revelation or an "antirevelation" effect, even when both items were studied or nonstudied, is incongruent with this explanation. The authors argue that revelation decrements familiarity, and this results in a more liberal criterion shift. They also argue that their theory is more consistent with previous empirical data.

An investigation of everyday prospective memory

Prospective memory, remembering to carry out one's planned activities, was investigated using a naturalistic paradigm. Three experiments, with a total of 405 participants, were conducted. The goal was to demonstrate that the cognitive processing underlying successful everyday prospective remembering involves components other than mere "memory." Those components are probably best represented as individual differences in various cognitive capacities. More specifically, metamemory, attentional capacities, and planning processes that reprioritize intentions according to the demands of everyday life may determine how people actually accomplish the plans they establish for themselves. The results of these experiments suggest that researchers interested in the topic will have to contend with a multidimensional set of factors before any comprehensive understanding of prospective remembering can be realized.

Optimal shortening velocity (V/Vmax) of skeletal muscle during cyclical contractions: length-force effects and velocity-dependent activation and deactivation

The force-velocity relationship has frequently been used to predict the shortening velocity that muscles should use to generate maximal net power output. Such predictions ignore other well-characterized intrinsic properties of the muscle, such as the length-force relationship and the kinetics of activation and deactivation (relaxation). We examined the effects of relative shortening velocity on the maximum net power output (over the entire cycle) of mouse soleus muscle, using sawtooth strain trajectories over a range of cycle frequencies. The strain trajectory was varied such that the proportion of the cycle spent shortening was 25, 50 or 75 % of the total cycle duration. A peak isotonic power output of 167 W kg-1 was obtained at a relative shortening velocity (V/Vmax) of 0.22. Over the range of cyclical contractions studied, the optimal V/Vmax for power production ranged almost fourfold from 0.075 to 0.30, with a maximum net power output of 94 W kg-1. The net power output increased as the proportion of the cycle spent shortening increased. Under conditions where the strain amplitude was high (i.e. low cycle frequencies and strain trajectories where the proportion of time spent shortening was greater than that spent lengthening), the effects of the length-force relationship reduced the optimal V/Vmax below that predicted from the force-velocity curve. At high cycle frequencies and also for strain trajectories with brief shortening periods, higher rates of activation and deactivation with increased strain rate shifted the optimal V/Vmax above that predicted from the force-velocity relationship. Thus, the force-velocity relationship alone does not accurately predict the optimal V/Vmax for maximum power production in muscles that operate over a wide range of conditions (e.g. red muscle of fish). The change in the rates of activation and deactivation with increasing velocity of stretch and shortening, respectively, made it difficult to model force accurately on the basis of the force-velocity and length-force relationships and isometric activation and deactivation kinetics. The discrepancies between the modelled and measured forces were largest at high cycle frequencies.

Event-based prospective memory and executive control of working memory

In 5 experiments, the character of concurrent cognitive processing was manipulated during an event-based prospective memory task. High- and low-load conditions that differed only in the difficulty of the concurrent task were tested in each experiment. In Experiments 1 and 2, attention-demanding tasks from the literature on executive control produced decrements in prospective memory. In Experiment 3, attention was divided by different loads of articulatory suppression that did not ultimately lead to decrements in prospective memory. A high-load manipulation of a visuospatial task requiring performance monitoring resulted in worse prospective memory in Experiment 4, whereas in Experiment 5 a visuospatial task with little monitoring did not. Results are discussed in terms of executive functions, such as planning and monitoring, that appear to be critical to successful event-based prospective memory.

Event-based prospective memory and executive control of working memory

In 5 experiments, the character of concurrent cognitive processing was manipulated during an event-based prospective memory task. High- and low-load conditions that differed only in the difficulty of the concurrent task were tested in each experiment. In Experiments 1 and 2, attention-demanding tasks from the literature on executive control produced decrements in prospective memory. In Experiment 3, attention was divided by different loads of articulatory suppression that did not ultimately lead to decrements in prospective memory. A high-load manipulation of a visuospatial task requiring performance monitoring resulted in worse prospective memory in Experiment 4, whereas in Experiment 5 a visuospatial task with little monitoring did not. Results are discussed in terms of executive functions, such as planning and monitoring, that appear to be critical to successful event-based prospective memory.

The effects of length trajectory on the mechanical power output of mouse skeletal muscles

The effects of length trajectory on the mechanical power output of mouse soleus and extensor digitorum longus (EDL) muscles were investigated using the work loop technique in vitro at 37 degrees C. Muscles were subjected to sinusoidal and sawtooth cycles of lengthening and shortening; for the sawtooth cycles, the proportion of the cycle spent shortening was varied. For each cycle frequency examined, the timing and duration of stimulation and the strain amplitude were optimized to yield the maximum power output. During sawtooth length trajectories, power increased as the proportion of the cycle spent shortening increased. The increase in power was attributable to more complete activation of the muscle due to the longer stimulation duration, to a more rapid rise in force resulting from increased stretch velocity and to an increase in the optimal strain amplitude. The power produced during symmetrical sawtooth cycles was 5-10 % higher than during sinusoidal work loops. Maximum power outputs of 92 W kg-1 (soleus) and 247 W kg-1 (EDL) were obtained by manipulating the length trajectory. For each muscle, this was approximately 70 % of the maximum power output estimated from the isotonic force-velocity relationship. We have found a number of examples suggesting that animals exploit prolonging the shortening phase during activities requiring a high power output, such as flying, jet-propulsion swimming and vocalization. In an evolutionary context, increasing the relative shortening duration provides an alternative to increasing the maximum shortening velocity (Vmax) as a way to increase power output.

In vivo performance of trunk muscles in tree frogs during calling

We used high-speed video and electromyography (EMG) to measure in vivo performance of the trunk muscles (external obliques) in two related species of North American gray tree frogs, Hyla versicolor and Hyla chrysoscelis. Both species produce trilled calls with high sound intensity, but the sound pulse frequency within calls in H. chrysoscelis is twice that in H. versicolor. In both species, sound pulse frequency is directly correlated with the active contractions of the trunk muscles. The length trajectory during contraction and relaxation displays a saw-tooth pattern with a longer shortening phase compared with the lengthening phase. The longer time spent shortening may enhance power production, because the shortening phase is the active part of the cycle during which the muscle produces positive work. A similar total strain (approximately 21 % and approximately 19 % in H. versicolor and H. chrysoscelis respectively) is achieved in the first few pulses, and during subsequent pulses the muscle cycles with a reduced pulse strain (approximately 12 % and approximately 7.3 % in H. versicolor and H. chrysoscelis respectively). The higher pulse frequencies of H. chrysoscelis are thus associated with lower pulse strains. The EMG pattern is different in the two species. A single EMG stimulus occurs for each cycle in H. chrysoscelis, but two stimuli per cycle are found in H. versicolor. Indirect evidence suggests that the initial phase of shortening during a pulse is partly due to elastic recoil of the trunk.

Work and power output in the hindlimb muscles of Cuban tree frogs Osteopilus septentrionalis during jumping

It has been suggested that small frogs use a catapult mechanism to amplify muscle power production during the takeoff phase of jumping. This conclusion was based on an apparent discrepancy between the power available from the hindlimb muscles and that required during takeoff. The present study provides integrated data on muscle contractile properties, morphology and jumping performance that support this conclusion. We show here that the predicted power output during takeoff in Cuban tree frogs Osteopilus septentrionalis exceeds that available from the muscles by at least sevenfold. We consider the sartorius muscle as representative of the bulk of the hindlimb muscles of these animals, because this muscle has properties typical of other hindlimb muscles of small frogs. At 25 degrees C, this muscle has a maximum shortening velocity (Vmax) of 8.77 +/- 0.62 L0 s-1 (where L0 is the muscle length yielding maximum isometric force), a maximum isometric force (P0) of 24.1 +/- 2.3 N cm-2 and a maximum isotonic power output of 230 +/- 9.2 W kg-1 of muscle (mean +/- S.E.M.). In contrast, the power required to accelerate the animal in the longest jumps measured (approximately 1.4 m) is more than 800 W kg-1 of total hindlimb muscle. The peak instantaneous power is expected to be twice this value. These estimates are probably conservative because the muscles that probably power jumping make up only 85% of the total hindlimb muscle mass. The total mechanical work required of the muscles is high (up to 60 J kg-1), but is within the work capacities predicted for vertebrate skeletal muscle. Clearly, a substantial portion of this work must be performed and stored prior to takeoff to account for the high power output during jumping. Interestingly, muscle work output during jumping is temperature-dependent, with greater work being produced at higher temperatures. The thermal dependence of work does not follow from simple muscle properties and instead must reflect the interaction between these properties and the other components of the skeletomuscular system during the propulsive phase of the jump.

Processing strategies and secondary memory in very rapid forgetting

When a memory test is unexpected, recall performance is quite poor at retention intervals as short as 2-4 seconds. Orienting tasks that change encoding conditions are known to affect forgetting in such "very rapid forgetting" paradigms where people are misled to believe that recall will not be required. We evaluated the hypothesis that differences in forgetting among orienting tasks are attributable to contributions of secondary memory during encoding in two experiments. In Experiment 1, short-term recall performance was inversely related to task demands during encoding, although long-term memory performance was not. Task demands were assessed by making the duration of stimulus presentation dependent on the time required to perform three different orienting tasks. In Experiment 2, we compared performance of that variable-length stimulus presentation to the fixed-length presentation used in most prior research. The results suggested that additional encoding or rehearsal time does not have an appreciable impact on short-term performance. Thus, differences in forgetting appeared to be a function of the contribution of secondary memory rather than a function of the time available to engage in primary memory rehearsal strategies.

Muscular force in running turkeys: the economy of minimizing work

During running, muscles and tendons must absorb and release mechanical work to maintain the cyclic movements of the body and limbs, while also providing enough force to support the weight of the body. Direct measurements of force and fiber length in the lateral gastrocnemius muscle of running turkeys revealed that the stretch and recoil of tendon and muscle springs supply mechanical work while active muscle fibers produce high forces. During level running, the active muscle shortens little and performs little work but provides the force necessary to support body weight economically. Running economy is improved by muscles that act as active struts rather than working machines.

How examples may (and may not) constrain creativity

Three experiments were performed to test Smith, Ward, and Schumacher's (1993) conformity hypothesis-that people's ideas will conform to examples they are shown in a creative generation task. Conformity was observed in all three experiments; participants tended to incorporate critical features of experimenter-provided examples. However, examination of total output, elaborateness of design, and the noncritical features did not confirm that the conformity effect constrained creative output in any of the three experiments. Increasing the number of examples increased the conformity effect (Experiment 1). Examples that covaried features that are naturally uncorrelated in the real world led to a greater subjective rating of creativity (Experiment 2). A delay between presentation and test increased conformity (Experiment 3), just as models of inadvertent plagiarism would predict. The explanatory power of theoretical accounts such as activation, retrieval blocking, structured imagination, and category abstraction are evaluated.

Power output of scallop adductor muscle during contractions replicating the in vivo mechanical cycle

Because measurements on isolated skeletal muscles are often made with limited knowledge of in vivo kinematics, predictions of mechanical performance during natural movements are subject to considerable uncertainties. We used information on the in vivo length cycle and phase of activation of the scallop adductor during swimming at 10 degrees C to design an in vitro contractile regime that replicated the natural cycle. Replicating the in vivo length cycle and stimulation regime resulted in power output during cyclic contractions that matched in vivo performance both qualitatively and quantitatively. When sinusoidal length changes were used instead of the natural length trajectory, the adductor muscle produced a similar average power output (approximately 30 W kg-1 at 1.9 Hz), but the distribution of power throughout the cycles was quite different. We examined the instantaneous force-velocity properties during cyclic contractions and found that the muscle operated on or near its isotonic force-velocity curve for only 30-40% of the time required for shortening. During sinusoidal length cycles, the force-velocity trajectory was quite different. We conclude that during cyclic contractions the isotonic force-velocity curve of skeletal muscle sets an approximate boundary to the force-velocity trajectory, but the shape of this trajectory, and thus the distribution of power output, depends on the pattern of length change.

Jumping performance of hylid frogs measured with high-speed cine film

Jumping performance at 20 degrees C was assessed in five species of hylid frogs using high-speed cine film. Mean takeoff velocities (Vt) varied from 1.5 to 2.4 ms-1 among the species. Peak Vt varied from 1.9 to 2.9 ms-1. Body-mass-specific power output averaged over the entire takeoff period varied from 29 to 91 W kg-1 during the jumps with the highest takeoff velocities. These values are similar to those predicted from jumping distance. As the mass of muscles available to power the jump probably amounts to no more than 17% of the body mass, average muscle-mass-specific power can be over 500 W kg-1. The performance during jumping is even more impressive in view of the fact that the peak power during takeoff is about twice the average power. These frogs must use elastic storage to redistribute power during takeoff to produce the peak power required and may use pre-storage of elastic energy to boost the average power available.

Eliciting cryptomnesia: unconscious plagiarism in a puzzle task

In three experiments we investigated cryptomnesia (unconscious plagiarism) and source memory using a word-search puzzle task. Subjects first alternated with a "computer partner" in locating words from 4 puzzles. They then attempted to recall their previously generated items as well as to locate additional new words. Substantially more plagiarism was committed in these tasks than was observed in a study by A. S. Brown and D. R. Murphy (1989), in which Ss generated category exemplars. Manipulations of retention interval (Experiment 1) and degree of encoding (Experiments 2a and 2b) reliably influenced plagiarism rates. Source confusions from a modified recognition memory task (Experiment 3) were used as the basis for a unitary relative strength model to explain both source and occurrence (item) forgetting.

Eliciting cryptomnesia: unconscious plagiarism in a puzzle task

In three experiments we investigated cryptomnesia (unconscious plagiarism) and source memory using a word-search puzzle task. Subjects first alternated with a "computer partner" in locating words from 4 puzzles. They then attempted to recall their previously generated items as well as to locate additional new words. Substantially more plagiarism was committed in these tasks than was observed in a study by A. S. Brown and D. R. Murphy (1989), in which Ss generated category exemplars. Manipulations of retention interval (Experiment 1) and degree of encoding (Experiments 2a and 2b) reliably influenced plagiarism rates. Source confusions from a modified recognition memory task (Experiment 3) were used as the basis for a unitary relative strength model to explain both source and occurrence (item) forgetting.

Contractile properties of the striated adductor muscle in the bay scallop Argopecten irradians at several temperatures

The isometric and isotonic contractile properties of the cross-striated adductor muscle of the bay scallop (Argopecten irradians) were measured in vitro at 10, 15 and 20 degrees C. The length at which twitch force was maximal as a function of the closed length in situ (L0/Lcl) averaged 1.38 +/− 0.01 (mean +/− S.E.M.) at 10 degrees C. This length is very close to the typical length at maximum gape during natural swimming at this temperature. Passive force was very low over the range of lengths measured here; at L0, passive force averaged approximately 0.08 N cm-2, or only 0.5% of the corresponding peak twitch force. The mean peak isometric twitch force (Ptw,max) at 10 degrees C was 21.43 +/− 0.68 N cm-2 (S.E.M.), and the ratio of peak twitch force to tetanic force (Ptw,max/P0) averaged 0.89 +/− 0.01. Temperature did not affect either twitch force (Ptw), once fatigue was taken into account, or Ptw,max/P0. In contrast, the time-related properties of twitch contractions (latent period, tL; time to peak tension, tPtw; and time from peak tension to half-relaxation, t50%R) were positively modified by temperature at all temperatures measured (Q10 > 1.8). All three properties were more temperature-sensitive over the range 10–15 degrees C than over the range 15–20 degrees C. The force-velocity relationships of the striated adductor muscle were fitted to the hyperbolic-linear (HYP-LIN) equation. The force-velocity curves of the striated adductor muscle of the scallop were strongly influenced by temperature. Maximal velocity at zero force (Vmax), and therefore maximal power output, increased significantly with temperature. The Q10 over the temperature range 10–15 degrees C (1.42) was significantly lower than that over the range 15–20 degrees C (2.41). The shape of the force-velocity relationship, assessed through comparisons of the power ratio (Wmax/VmaxP0), was not influenced by temperature.

Reduction in microtubule dynamics in vitro by brain microtubule-associated proteins and by a microtubule-associated protein-2 second repeated sequence analogue

Microtubule-associated protein (MAP) binding to assembled microtubules (MTs) can be reduced by the addition of polyglutamate without significant MT depolymerization or interference with MT elongation reactions. Ensuing polymer length redistribution in MAP-depleted MTs occurs on a time scale characteristic of that observed with MAP-free MTs. The redistribution phase occurs even in the absence of mechanical shearing and without appreciable effects from end-to-end annealing, as indicated by the time course of incremental changes in polymer length and MT number concentration. We also observed higher rates of MT length redistribution when the [MAP]/[tubulin] ratio was decreased. Together, these results demonstrate that MT length redistribution rates are greatly influenced by MAP content, and the data are compatible with the dynamic instability model. We also found that a peptide analogue corresponding to the second repeated sequence in the MT-binding region of MAP-2 can also markedly retard MT length redistribution kinetics, a finding that accords with the ability of this peptide to promote tubulin polymerization in the absence of MAPs and to displace MAP-2 from MTs. These results provide further evidence that MAPs can modulate MT assembly/disassembly dynamics and that peptide analogues can mimic the action of intact MAPs without the need for three contiguous repeated sequences in the MT-binding region.

Mechanical performance of scallop adductor muscle during swimming

Mechanical performance of skeletal muscle has long been the subject of intense interest, but the details of in vivo performance of individual skeletal muscles during normal locomotion remain largely unknown. Performance in vitro has been described with considerable precision under simplified loading conditions. The force production and shortening velocity of most muscles, however, probably change continuously during natural movements. Therefore, modelling in vivo performance on the basis of in vitro contractile properties is subject to large degrees of uncertainty. Designing in vitro experiments that effectively examine the limits of mechanical performance requires increasing knowledge of precisely how muscles are used during normal movements. We report here measurements of the mechanical performance of the adductor muscle in scallops during jet-propulsion swimming. Swimming in scallops is powered solely by the striated portion of the single adductor muscle. Exploiting this simple locomotor morphology with simultaneous high-resolution measurements of pressure and flow rate, we have recorded nearly instantaneous measurements of the performance of a single skeletal muscle during normal locomotion.

Deactivation rate and shortening velocity as determinants of contractile frequency

The kinetic properties of muscle that could influence locomotor frequency include rate of activation, rate of cross-bridge "attachment", intrinsic shortening velocity, and rate of deactivation. The latter two mechanisms are examined using examples from high-speed running in lizards and escape swimming in scallops. During running, inertial loading and elastic energy storage probably mitigate the effects of thermal alterations in intrinsic muscle shortening velocity. The result is a rather low thermal dependence of stride frequency over a 15-20 degree C temperature range. However, at lower temperatures, the longer times required for deactivation cause the thermal dependence of frequency to increase greatly. Scallops use a single muscle to swim by jet propulsion. In vivo shortening velocity in these animals also shows a low thermal dependence. As with high-speed running, the mechanics of jet propulsion may limit the effects of thermally induced changes in intrinsic shortening velocity. The largest thermal effect during swimming is on the initial phase of valve opening. The effects of temperature on the rate of deactivation of the adductor muscle could play an important role in limiting reextension of the muscle, which is dependent on elastic energy storage in the hinge ligament. These examples illustrate that the relative importance of various intrinsic contractile properties in controlling locomotor performance depends on the mechanics of the movements.

Regulation of glycolysis in the pectoralis muscles of seasonally acclimatized American goldfinches exposed to cold

Regulation of glycolysis was assessed in winter- and summer-acclimatized goldfinches (Carduelis tristis). We exposed birds to a thermo-neutral temperature (30 degrees C), moderate cold (-15 degrees C), and severe cold (0 degrees C in an atmosphere of 21% O2-79% He), and then measured concentrations of glycogen, glycolytic intermediates, and citrate in the pectoralis muscles. Winter birds used less glycogen when exposed to moderate cold than did summer birds, confirming the carbohydrate sparing noted by Marsh and Dawson [Am. J. Physiol. 242 (Regulatory Integrative Comp. Physiol. 11): R563-R569, 1982]. However, depletion of muscle glycogen did not correlate with thermoregulatory failure in this study. Concentrations of glucose 6-phosphate and fructose 6-phosphate in the pectoralis muscles were approximately 1.9 and 0.3 mumol/g wet mass in birds exposed to thermoneutral temperatures. The levels of these intermediates fell 50-70% under conditions known to enhance flux through glycolysis as indicated by increased glucose turnover and glycogen depletion. This information identifies phosphofructokinase (PFK) as a major regulated step in glycolysis in these highly aerobic skeletal muscles. Winter birds maintained the inhibition of this step under conditions of moderate cold. However, concentrations of citrate, which have been hypothesized to be an important inhibitor of PFK, did not correlate with the observed pattern of inhibition. Therefore, if the enhanced beta-oxidative capacity of winter birds is important in the regulation of glycolysis, a mechanism other than the accumulation of citrate may be involved.

Secondary memory and very rapid forgetting

Studies of recall in the absence of expectancy (e.g., Muter, 1980) have suggested that forgetting from primary memory is much more rapid than previously assumed. Two experiments examined the role of secondary memory, as reflected by encoding strategies, in determining this rate of forgetting. Experiment 1 demonstrated that the type of encoding specified by orienting tasks can influence recall in a traditional Brown-Peterson task. Experiment 2 demonstrated a similar pattern of effects of orienting task in the Muter task when recall was not expected, despite much more rapid forgetting. The type of encoding engaged by the orienting tasks did not account for Muter's results. Expectancy and orienting task appear to have separable influences on resource allocation during encoding. The presence of secondary memory influences at even the shortest retention interval indicates that forgetting from primary memory may be even more rapid than has been proposed.